Steroids MSc 4th sem

 steroid :- 

introduction :- Steroids constitute a group of structural related organic compounds that are widely distributed both in plants and animals kingdom

Basically steroids are the natural products which are extracted from the nature and can also be synthesised in laboratory .

Steroids have 1,2-cyclopentenophenanthrene nuclei in their structure 

steroid include compounds with wide variation in the structure and and encomposed a variety of components of vital importance to life such as cholesterol, bile acids, vitamin D, sex hormones and antibiotic etc.  

Any compound which gives Diel's hydrocarbon with Se distillation is defined as steroid.

Diel's hydrocarbon:-  Diel's hydrocarbon is a solid with melting point 126 to 127 degree Celsius 

its molecular formula is C18H26

 it was first obtained when steroids are distillated with Se.

 when steroids are distillated at 420 degree Celsius yields, mainly two hydrocarbons crysene and little picene.

 structure of Diel's hydrocarbon was confirmed by its synthesis, starting from 2-(1-nephthyl)-ethyl magnesium bromide and 2,5 dimethyl cyclopentanone.

 Sterols:- sterols are known as steroid alcohol , are a sub group of the steroids and an important class of organic molecules. steroids occur in animals and plant oil and fat . 

 They are crystalline compounds, and contain an alcoholic group they occur free or as ester of higher fatty acids and isolated from unsaponificable portion of oil and fat.

 

 Classification of on the basis of source:- 

 three types

 1. 200 sterols ( animal source )[ cholesterol, cholestanol, Coprosterol]

 2. phytosterols ( plant source)[Campesterol, sitosterol, stigmasterol]

 3.  Mycosterols( yeast and fungi source)[Ergosterol, vitamin D]

 Structure (nucleus and number)

 Gonane also known as steran or cyclopentanoperhydrophenanthrene, the simplest steroid and the nuclear of all steroids and sterols, is composed of C17 atoms in C-C bond forming and four fused ring in a three dimensional shape 

 the three cyclohexane ring A B and C forms the skeleton of perhydroderivative of phenanthrene.

 The D ring has cyclopentane structure .

 When the 2 methyl groups and B,C side chains (at C17) are present, the steroids are said to have cholestane frameworks sterols are forms of steroids with a hydroxyl group at position 3 and a skeletal derived from cholestane .

 All the steroids have this basic nucleus they very in the functional group attached and the side chain attached to these four rings.

 

cholesterol :- 

molecular formula of cholesterol is C27H46O and its melting point is 149 degree Celsius

 this is the sterol of higher animals occurring free or as fatty esters in all animal cells, particularly in the brain and spinal cord. cholesterol was first isolated from human ga stone.

 the main sources of cholesterol are the fish liver oil, the spinal cord of cattles .

 cholesterol is a white crystalline solid which is optically active .

 cholesterol is a waxy substance found normally in blood predominantly produced in liver but alsl found in food such as red meat, high fat cheese , butter eggs etc.

 cholesterol is essential for maintaining the good heart but to high concentration of cholesterol in the blood can leads to high blood pressure, heart disease etc. but good and healthy lifestyle can help to lower cholesterol level and the significant to reduce the risk.

 cholesterol travel in the blood transported in molecules called lipoprotein they are sphere shaped assemblies that keeps the cholesterol separated from the blood.

 There are two types of lipoproteins:-

 1. LDL(low density lipoprotein):;

 It is a bad cholesterol if there is too much LDL in blood it can slowly built in the arteries making them narrower which increases of heart diseases.

 2. high density lipoprotein (HDL):- 

  It is a good cholesterol

  It helps to remove excess cholesterol from the bloodstream and return it to the liver where it is broken down and passed out of the body.

   the structure of cholesterol was elucidated only after a tremendous amount of work particularly by wielard, windairs and their co-workers (1903-1932)

   

   structure determination :- 

   for the elucidation of cholesterol , firstly it is important to know the structure of cholesterol 

   the molecule consists of a side chain and a nucleus composed of four rings . 

   these rings are usually designed A,B,C and D

    it also contains two methyl group at C-10 and C-30

    THE STRUCTURE ELLUSIDATION OF CHOLESTEROL CAN BE DIVIDED INTO FOUR PARTS 

   1 STRUCTURE OF THE RING SYSTEM

   2 POSITION OF HYDROXYL GROUP AND DOUBLE BOND

   3 NATURE AND POSITION OF SIDE CHAIN

   4   POSITION OF 2 ANGULAR METHYL GROUPS

    Structure of the ring system molecular:- Molecular formula of cholesterol is C27H46O

     on acetylation, cholesterol forms monoacetal and this reaction confirms the present of a hydroxy group 

     choesterol is treated with H2 in the presence of catalyst and  with bromine(Br2) it absorbs one mole of H2 and 1 mole of Br2 which indicates the presence of 1 double bond

    Cholesterol shows the following set of reactions:- 

    This leads to the following conclusion:-  

     1 to 2 prove the presence of 1 double bond 

     2 to 3 (a ketone) shows that cholesterol is secondary alcohol 

     3 to 4 cholestane is a saturated hydrocarbon and corresponds to the general formula CnH2n - 6 and hence cholesterol is a tetracyclic compound

      the ring in the steroid nucleus were opened to give a dicarboxylic acid and the relative positions of the two carboxylic groups  with respect to  each other were determined by the application of blanc's  rule :- which states that on heating with acetic anhydride, 1,5 dicarboxylic acids form cyclic anhydride and 1,6 - dicarboxylic acids form cyclopentanones with eliminatiom of CO2. 

ENZYMES MSC 4TH SEM

 Enzymes

• 6.1 An Introduction to Enzymes 183
• 6.2 How Enzymes Work 186
• 6.3 Enzyme Kinetics as an Approach to Understanding mechanism 194
• 64 Examples of Enzymatic Reactions 205 
• 6.5 Regulatory Enzymes 220

Introduction:- 

• There are two fundamental conditions for life.
•  First, the organism must be able to self-replicate; 
• second, it must be able to catalyze chemical reactions efficiently and selectively. 
• The central importance of catalysis may seem surprising, but it is easy to demonstrate. 
• As living systems make use of energy from the environment.
•  Many of them, for example, consume substantial amounts of sucrose-common table sugar as a kind of fuel, usually in the form of sweetened foods and drinks.
•  The conversion of sucrose to CO2, and H₂O in the presence of oxygen is a highly exergonic process, releasing free energy that we can use to think, move, taste and see.
•  However, a bag of sugar can remain on the shelf for years without any obvious conversion to CO₂ and H2O. 
• Although this chemical process is thermodynamically favorable, it is very slow! 
• Yet when sucrose is consumed by a human (or almost any other organism), it releases its chemical energy in seconds. 
• The difference is catalysis. 
• Without catalysis, chemical reactions such as sucrose oxidation could not occur on a useful time scale, and thus could not sustain life.
• In this chapter, then we turn our attention to the reaction catalysts of biological systems: the enzymes, the most remarkable and highly specialized protein. 
• Enzymes have extraordinary catalytic power, often far greater than that of synthetic or inorganic catalysts
• They have a high degree of specificity for their substrates, they accelerate chemical reactions tremendously, and they function in aqueous solutions under very mild conditions of temperature and pH.
•  Few nonbiological catalysts have all these properties. 
• Enzymes are central to every biochemical process. 
• Acting in organized sequences, they catalyze the hundreds of stepwise reactions that degrade nutrient molecules, conserve and transform chemical energy, and make biological macromolecules from simple precursors.

 The study of enzymes has immense practical importance. 

• In some diseases, especially inheritable genetic disorders, there may be a deficiency or even a total absence of one or more enzymes. 
• Other disease conditions may be caused by excessive activity of an enzyme.
•  Measurements of the activities of enzymes in blood plasma, erythrocytes, or tissue samples are important in diagnosing certain illnesses.
•  Many drugs act through interactions with enzymes. 
• Enzymes are also important practical tools in chemical engineering, food technology, and agriculture.
• We begin with descriptions of the properties of enzymes and the principles underlying their catalytic power, then introduce enzyme kineties, a discipline that provides much of the framework for any discussion of enzymes. 
• Specific examples of enzyme mechanisms are then provided, illustrating principles introduced earlier in the chapter. 
• We end with a discussion of how enzyme activity is regulated

6.1 An Introduction to Enzymes

• Much of the history of biochemistry is the history of enzyme research, Biological catalysis was first recognized and described in the late 1700s, in studies on the digestion of meat by secretions of the stomach. 
• Research continued in the 1800s with examinations of the conversion of starch to sugar by saliva and various plant extracts. 
• In the 1850s, Louis Pasteur concluded that fermentation of sugar into alcohol by yeast is catalyzed by "ferments." 
• He postulated that these ferments were in- separable from the structure of living yeast cells; this view, called vitalism, prevailed for decades. 
• Then in 1897 Eduard Buchner discovered that yeast extracts could ferment, sugar to alcohol, proving that fermentation was promoted by molecules that continued to function when removed from cells 
• Buchner's experiment at once marked the end of vitalistic notions and the dawn of the science of biochemistry. 
• Frederick W. Kühne later gave the name enzymes to the molecules detected by Buchner.
• The isolation and crystallization of urease by James Sumner in 1926 was a breakthrough in early enzyme studies.
•  Summer found that urease crystals consisted entirely of protein, and he postulated that all enzymes are proteins. 
• In the absence of other examples, this idea remained controversial for some time.
•  Only in the 1930s was Sumner's conclusion widely accepted, after John Northrop and Moses Kunitz crystallized pepsin, trypsin, and other digestive enzymes and found them also to be proteins.
•  During this period, J. B. S. Haldane wrote a treatise entitled Enzymes.
•  Although the molecular nature of enzymes was not yet fully appreciated, Haldane made the remarkable suggestion that weak bonding interactions between an enzyme and its substrate might be. used to catalyze a reaction.
•  This might lies at the heart of our current understanding of enzymatic catalysis.
• Since the latter part of the twentieth century, thousands of enzymes have been purified, their structures Can elucidated, and their mechanisms explained.

Most Enzymes Are Proteins

With the exception of a small group of catalytic RNA molecules (Chapter 26), all enzymes are proteins. 

Their catalytic activity depends on the integrity of their native protein conformation.

 If an enzyme is denatured or dissociated into its subunits, catalytic activity is usually lost. 

If an enzyme is broken down into its component amino acids, its catalytic activity is always destroyed 

This the primary, secondary, tertiary, and quaternary structures of protein enzymes are essential to their catalytic activity.

Enzymes, like other proteins, have molecular weights ranging from about 12,000 to more than 1 million. 

Some enzymes require no chemical groups for activity other than their amino acid residues.

 Others require an additional chemical component called a cofactor either one or more inorganic ions, such as Fe, Mg, Mr, or Zn (Table 6-1), or a complex organic or metallo organic molecule called a coenzyme. 

Coenzymes act as transient (Table 6-2). 

Most are derived from vitamins, organic nutrients required in small amounts in the diet. 

We consider coenzymes in more detail as we encounter them in the metabolic pathways discussed in Part II 

Some enzymes require both a coenzyme and one or more metal ions for activity. 

A coenzyme or metal ion that is very tightly or even covalently bound to the enzyme protein is called a prosthetic group.

 A complete, catalytically active enzyme together with its bound coenzyme and/or metal ions is called a holoenzyme. 

The protein part of such an enzyme is called the apoenzyme or apoprotein. 

Finally, some enzyme proteins are modified covalently by phosphorylation, glycosylation, and other processes. 

Many of these alterations are involved in the regulation of enzyme activity

Enzymes Are Classified by the Reactions They Catalyze

Many enzymes have been named by adding the suffix "ase" to the name of their substrate or to a word or phrase describing their activity.

 Thus urease catalyzes hydrolysis of urea, and DNA polymerase catalyzes the polymerization of nucleotides to form DNA.

 Other enzymes were named by their discoverers for a broad function, before the specific reaction catalyzed was known, 

For example, an enzyme known to act in the digestion of foods was named pepain, from the Greek pepsis, "digestion." and lysozyme was named for its ability to lyse (break down) bacterial cell walls. 

Still others were named for their source: trypsin, named in part from the Greek trypsin, "to wear down," was obtained by nabbing pancreatic tissue with glycerin. 

Sometimes the same enzyme has two or more names, or two different enzymes have the same name. 

Because of such ambiguities, and the ever-increasing number of newly discovered enzymes, biochemists, by interational agreement, have adopted a system for naming and classifying enzymes 

This system divides enzymes into six classes, each with subclasses, based on the type of reaction catalyzed (Table 6-3). 

Each enzyme is assigned a four-part classification number and a systematic name, which identifies the reaction it, catalyse. 

As an example, the formal systematic name of the enzyme catalyzing the reaction class (phosphotransferase);

 the third number (1), a phosphotransferase with a hydroxyl group as acceptor and the fourth number (1), -glucose as the phosphoryl group acceptor

 For many enzymes, a common name is more frequently used in this case hexokinase.

 A complete list and description of the thousands of known enzymes is maintained by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology

 (www.chem.quid.ac.uk/ibmb/enzyme). 

This chapter is devoted primarily to principles and properties common to all enzymes

SUMMARY 6.1 An Introduction to Enzymes

Life depends on powerful and specific catalysts the enzymes. Almost every biochemical reaction is catalyzed by an enzyme. 

With the exception of a few catalytic RNAs, all known enzymes are proteins. 

Many require nonprotein coenzymes or cofactors for their catalytic function.

ATP D-glucose-ADP+ D-gluse 6-phosphate

is ATP ghase phosphotransferase, which indicates that it catalyzes the transfer of a phosphoryl group from ATP to glucose 

It Ergyme Commission number (E.C. mum. ber) is 2.7.1.1. The first number (2) denotes the class name (transferase); the second number (7), the sub

Enzymes are classified according to the type of reaction they catalyze. All enzymes have formal

E.C. numbers and names, and most have trivial

To understand catalysis, we must first appreciate, the important distinction between reaction equilibria and reaction rates. 

The function of a catalyst is to increase the rate of a reaction.

 Catalysts do not affect reaction equilibria.

 Any reaction, such as SP, can be described by a reaction coordinate diagram (Fig. 6-2), a picture of the energy changes during the reaction. 

As discussed in Chapter 1, energy in biological systems is described in terms of free energy, G. 

In the coordinate diagram, the free energy of the system is plotted against. 

the progress of the reaction (the reaction coordinate). 

The starting point for either the forward or the reverse reaction is called the ground state, the contribution to the free energy of the system by an average molecule (S or P) under a given set of conditions.

AGURE 6-1 inding of a substrate to an mayme at the active site. The enzyme dymotrypsin, with bound substrate in red (PDB ID 70CH Some key activeste amino acid residues appear as a red splotchun the ymme surface.

6.2 How Enzymes Work

The enzymatic catalysis of reactions is essential to living systems, Under biologically relevant conditions, uncatalyzed reactions tend to be slow-most biological molecules are quite stable in the neutral pH, mild temperature, aqueous environment inside cells, Further more, many common chemical processes are unfavorable or unlikely in the cellular environment, such as the transient formation of unstable charged intermediates or the collision of two or more molecules in the precise orientation required for reaction. 

Reactions required to digest food, send nerve signals, or contract a misele simply do not occur at a useful rate without catalysis

An enzyme circumvents these problems by providing a specific environment within which a given reaction can occur more rapidly. 

The distinguishing feature of an enzyme-catalyzed reaction is that it takes place within the confines of a pocket on the enzyme called the active site (Fig. 6-1). 

The molecule that is bound in the active site and acted upon by the enzyme is called the substrate. 

The surface of the active site is lined with amino acid residues with substituent grups that bind the substrate and catalyze its chemical transformation 

Often, the active site encloses a substrate, sequestering it completely from solution.

 The enzyme-substrate complex, whose existence was first proposed by Charles Adolphe Wurtz in 1880, is central to the action of enzymes. 

It is also the starting point for mathematical treatments that define the kinetic behaviour of enzyme catalyzed reactions and for theoretical descriptions of enzyme mechanisms.

Enzymes Affect Reaction Rates, Not Equilibria

A simple enzymatic reaction might be written

KEY CONVENTION: 

To describe the free-energy changes for reactions, chemists define a standand set of conditions (temperature 208 K; partial pressure of each gas 1 atm, or 101.3 kPa concentration of each solute I s) and express the free energy change for a reacting system under these conditions as AG", the standard free-energy change. 

Because biochemical systems commonly involve H concentrations far below 1 M, biochemists define a biochemical standard free-energy change, ∆G, the standard free-energy change at pH 7.0, we employ this definition throughout the book.    

The equilibrium between S and P reflects the difference in the free energies of their ground states. 

In the example shown in Figure 6-2, the free energy of the ground state of P is lower than that of S, so AG for the reaction is negative and the equilibrium favors P. 

The position and direction of equilibrium are not affected by any catalyst.

187

the appropriate enzyme is present, because the rate of the reaction is increased. This general principle is illustrated in the conver sion of sucrose and oxygen to carbon dioxide and water:

A favorable equilibrium does not mean that the SP conversion will occur at a detectable rate. The rate of a reaction is dependent on an entirely different parameter. There is an energy barrier between S and P the energy required for alignment of reacting groups, formation of transient unstable charges, bond re arrangements, and other transformations required for the reaction to proceed in either direction. This is illus trated by the energy "hill" in Figures 6-2 and 6-3, Tb undergo reaction, the molecules must overcome this barrier and therefore must be raised to a higher energy level. At the top of the energy hill is a point at which de cay to the S or P state is equally probable (it is downhill either way). This is called the transition state. The transition state is not a chemical species with any signif icant stability and should not be confused with a reac tion intermediate (such as ES or EP). It is simply a fleeting molecular moment in which events such as bond breakage, band formation, and charge development have proceeded to the precise point at which decay to either substrate or product is equally likely. The stiffer ence between the energy levels of the ground state and the transition state is the activation energy AG The rate of a reaction reflects this activation energy: a higher activation energy corresponds to a slower reaction Reaction rates can be increased by mising the tempera ture and/or pressure, thereby increasing the number of molecules with sufficient energy to overcome the energy barrier. Alternatively, the activation energy can be low ered by adding a catalyst (Fig. 6-3). Catalysts enhance maction rates by lowering activation energies

Enzymes are no exception to the rule that catalysts do not affect reaction equilibria. The bidirectional ar rows in Equation 6-1 nuke this point: any enzyme that catalyzes the reaction S-P also catalyzes the reaction PS. The role of enzymes is to accelerate the inter conversion of Sand P. The enzyme is not used up in the process, and the equilibrium point is unaffected. How ever, the reaction reaches equilibrium much faster when

Transition state (1) A

اد

Reaction coordinate

FIGURE 6-3 Reaction coordinate diagram comparing enzyme

catalyzed and uncatalyzed reactions in the reactions→P the 15 and EP intermediates occipy mnima in the energy progress curve of the enzyme-catalyzed reaction. The tems AG and AC comespond to the activation energy ker the uncatalyad reaction and the overall activation ausgy for the catalyzed seactkin, respectively. The atha bon energy is lowerwhen the enzyme catalyzes the reaction

CulO 120, 1200, +11H₂O

This conversion, which takes place through a series of separate reactions, has a very large and negative AG and at equilibrium the amount of sucrose present is neg ligible. Yet sucrose is a stable compound, because the activation energy barrier that must be overcome before. sucrose reacts with oxygen is quite high. Sucrose can be red in a container with oxygen almost indefinitely without reacting. In cells, however, sucrose is readily broken down to CO, and HO in a series of reactions cal alyzed by enzymes. These enzymes not only accelerate the reactions, they organize and control them so that much of the energy released is recovered in other chem ical forms and made available to the cell for other tasks, The reaction pathway by which sucrose (and other sug ars) is broken down is the primary energy-yielding path way for cells, and the enzymes of this pathway allow the reaction sequence to proceed on a biologically useful time scale

Any reaction may have several steps, involving the formation and decay of transient chemical species called reaction intermediates A reaction intermediate is any species on the reaction pathway that has a finite. chemical lifetime (longer than a molecular vibration, -10 seconds). When the SP reaction is catalyzed i by an enzyme, the ES and EP complexes can be consid ered intermediates, even though S and P are stable chemical species (Ean 6-1); the ES and EP complexes occupy valleys in the reaction coordinate diagram (Fig. 6-3). Additional, less stable chemical intermediates of ten exist in the course of an eryme-catalyzed reaction. The interconversion of two sequential reaction interme diates thus constitutes a reaction step. When several steps occur in a reaction, the overall rate is determined by the step (or steps) with the highest activation en ergy, this is called the rate-limiting step in a simple case, the rate limiting step is the highest-energy point in the diagram for interconversion of S and P. In practice, the tate-limiting step can vary with reaction conditions, and for many enzymes several steps may have similar activation energies, which means they are all partially mate-limiting.

Activation energies are energy barriers to chemical reactions. These barriers are crucial to life itself. The rate - at which a molecule undergoes a particular reaction

In this chapter, lediterinerler to chemical species in the main pathway of a side eye-cataly reaction. In the c it of mutable pothwaysinlingmay ays (discussed in Part II), these term ured somewhat diffently. An entire uzymatic mation often referred to as a step in a pathway, and the prodad cainis (which is the sidstnite for the next eve in the pathway) is referred to an intermediate

" Hereditary and evolution" class 10th

 Topics to be covered

• Introduction
• What is Heredity?
• Inherited traits
• Mendel's experiments
• Laws of Inheritance
• Sex determination
• Evolution
• - Variations & its relation to Evolution
• Acquired vs. Inherited traits
• - Speciation
• -Evolution by stages
• Human evolution

What is Heredity?

• Passing of traits from parents/ancestors to offspring
• Genetics :- The branch of science which deal with the study of heredity

Heredity vs. Inheritance

Heredity

• The process by which characters are transferred from one generation to the next generation is called inheritance / heredity 
• The differences in traits of individuals of a progeny from each other and from their parents are called variations
• The branch of science which deals with inheritance and variation is called genetics

Inherited trait:

A trait that is genetically passed down from one generation to another

Inherited traits: Examples

Hair colour

. Eye colour

. Height

Shape of feet

. Ear lobes

How do the traits get inherited?

1. Mendel's Experiment

• Gregor Johann Mendel (1822-1884) is known as 'Father of Genetics'.
• Mendel performed his experiments with garden pea plant (Pisum sativum)
• He conducted artificial pollination/cross-pollination experiments using several true-breeding varieties having contrasting traits 
• He observed one trait at a time
• He hybridised plants with alternate forms of a single trait (Monohybrid cross). The seeds thus produced were grown to develop into plants of first filial generation (F₁) 
• Mendel then self-pollinated the F, plants to generate plants of second filial generation (F₂)
• Later, Mendel also crossed pea plants that differed in two characters (Dihybrid cross)

2. Mendel's Experimental Plant

Mendel selected garden pea as his experimental material because of the following reasons.

(1) It is an annual plant with a short life-cycle. So, several generations can be studied within a short period.

(2) It has perfect bisexual flowers containing both male and female parts

(3) The flowers are predominantly self-pollmating It is easy to get pure line for several generations.

(4) It is easy to cross-pollmate them because pollens from one plant can be introduced to the stigma of another plant by removing the anthers

(5) Pea plant produces a large number of seeds in one generation

(6) Pea plants could easily be raised, maintained and handled

 (7) A number of easily detectable contrasting characterstraits were available

3. Mendel's Observations

(1) F1 progenies always resembled one of the parents and trait of other parent was not seen

(2) F2 stage expressed both the parental traits in the proportion 3.1.

(3) The contrasting traits did not show any blending at either F1or F2 stage.

 (4) In dihybrid cross, he got identical results as in monohybrid cross

(5) He found that the phenotypes in F2 generation appeared in the ratio 3:1

(6) He found that the genotypic ration in F2 generation appeared in the ratio 1:2:1

4. Mendel's Laws of Inheritance

■ Based on his hybridisation experiments, Mendel proposed the laws of inheritance.

(i) Law of dominance (First law)

■ This law states that when two alternative forms alleles are present in an organism, only one factor expresses itself in F1 progeny and is called dominant while the other that remains masked is called recessive.

(ii) Law of segregation (Second law)

■ This law states that alleles of a pair segregate from each other during gamete formation, such that a gamete receives only one of the two factors. They do not show any blending.

iii) Law of independent assortment

According to this law the two factors of each character separate out independent of the factors of other characters at the time of gamete formation and get randomly rearranged in the offsprings producing both parental and new combinations of characters.

Sex Determination Mechanism :- 

Finalisation of sex at the time of zygote formation is called sex Determination .

XX-XY type :- 

Seen in many insects including humans .

Males have X and Y chromosomes along with autosomes and female have a pair of X chromosomes.

"Magnetic effect of electric current" class 10

 Topics to be covered:- 

• History of magnetism 
• Bar magnet 
• Magnety field
• Operated 's experiment 
• Magnetic field lines
• Magnetic field due to current carrying conductor due to magnetic field
• Electric motor 
• Electromagnetic induction
• Electric generator

Introduction:-

• Nail  attracted towards magnet.
• Refrigerator locked due to magnetic properties
• Metro doors use magnetism
• Electric motors and generators works on magnetism

Story of magnetism:- 

• Shepherd found some rocks that was attracted nail.
• People thought that rocks were magical and so called those rocks magnesia (word from magic)
• Later scientists give it a name magnetism.

Bar magnet:-

• Rectangular object that has a magnetic field .

Properties of bar magnet:-

• Align itself in the north south direction when suspended freely.
• North and South pole cannot be isolated.
• Like led repel and unlike poles attract .

• Not all materials are attracted by magnet.

Magnetic field::

• Region around a magnet where the magnet exerts its influence.

Magnetic field lines:- 

• Magnetic field is a vector quantity [magnitude + direction]
• Visual realization of magnetic field by bar magnet and iron filling experiment.
• Directions:- outside magnet:- North to South and Inside magnet:- South to North

Properties of magnetic field lines :-

• Form continuous closed loops
•  Tangent to magnetic field line at a given point specifies the direction of net magnetic field at that point
• Greater number of magnetic field lines per unit area stronger the magnetic field .
• Two magnetic field lines never intersect each other . If they do so that means it shows two directions at one point which is not possible. 

Operated experiment:- 

• Electricity and magnetism are very closely related .
• Operated observed the inter relation between electricity and magnetism.

Oersted experiment:- 

Observations:- 

• Magnetic compass needle deflected when current passes through a wire.
• A wire carrying electric current behave like a magnet.
• Deflection reverses as the direction of current is reversed.

Conclusion:- 

• A wire carrying electric current behave like a magnet.
• Moving charges produce a magnetic field in the surrounding region.

Magnetic field due to a current carrying 

• Straight conductor 
• Circular loop
• Solenoid

Magnetic field due to a current carrying straight conductor:-

• Magnitude of magnetic field produced at a given point increases as the current through the wire increases. 
• Magnetic field produced by a given current in a conductor decreases as the distance of the point from it increases.

Pattern of field lines:- 

• Concentric circles represent magnetic field around a current carrying straight wire.

Directions of magnetic field:- 

Right hand thumb rule :- If a current carrying straight conductor is held in your right hand such that thumb point towards the direction of current, then the wrapped fingers show direction of magnetic field lines.

Magnetic field due to a current carrying circular loop:-

• Every point on the wire carrying current would give rise to magnetic field appearing as straight lines at the centre of loop 

So

•  magnetic field is directly proportional to current 
• magnetic field is directly proportional to number of turns ,
• magnetic field is inversely proportional to square of distance 

Strength of magnetic field at the centre of coil (loop) depends upon:- 

Radius of coil:-

• Strength of magnetic field is inversely proportional to radius of coil . If radius increases, magnetic strength at the centre decreases.

Number of turns in the coil:- 

• As the number of turns in the coil increases , the magnetic field strength at the centre increases. This is because current in each circular turn is having the same direction thus field due to each turn add up .

The strength of current flowing in the coil:- 

• As the strength increases, the strength of magnetic field increases.

Maxwell Corkscrew Rule/ Right Hand rule:-

•  If we considered ourselves driving a corkscrew in the direction of current, then the direction of corkscrew is the direction of magnetic field.

Magnetic field due to a current carrying solenoid :-

• Solenoid is a coil wound into a tightly packed helix .
• Or 
• A coil of many circular turns of insulated copper wire wrapped in shape of cylinder.
• Field lines of a solenoid are similar to those of bar magnet.
• Field is uniform inside the solenoid.
• Strength of magnetic field is proportional to number of turns and magnitude of current.

Where do we use solenoid:- 

• Transformer creation

Electromagnet:- 

• Strong magnetic field produced inside the solenoid is used to magnetize the magnetic material like steel , soft iron , when placed inside the coil 

Magnetic field :- 

• Introduction of force due to magnetic field:- 
• A current carrying rod experiences a force perpendicular to its length and magnetic field 
• Direction of the force on the conductor depends upon:-
• - Direction of current and 
• - Directions of magnetic field

Fleming Left hand rule:-

Stretch your thumb , forefinger and middle finger of your left hand in such a way that they are mutually perpendicular to each other. If the first finger shows the direction of magnetic field and middle finger show the direction of current then the thumb will show the direction of motion of conductor.

Fleming ' left hand rule demonstration:- 

A relationship between direction of magnetic field, current and the force on the conductor .

Note :- downward :- inward

Upward:- outward

Application:- magnetic field and force exerted by it:- 

• Electric motor ,
• Electric generator
• Loudspeaker,
• Microphone,
• Measuring instruments etc.

Magnetism in medicine

• An electric current always produces a magnetic field. 
• Even weak ion currents that travel along the nerve cells in our body produce magnetic fields. 
• When we touch something, our nerves carry an electric impulse to the muscles we need to use. 
• This impulse produces a temporary magnetic field.
•  These fields are very weak and are about one-billionth of the earth's magnetic field. 
• Two main organs in the human body where the magnetic field produced is significant, are the heart and the brain. 
• The magnetic field inside the body forms the basis of obtaining the images of different body parts.
•  This is done using a technique called Magnetic Resonance Imaging (MRI). 
• Analysis of these images helps in medical diagnosis. 

• Magnetism has, thus got important uses in medicine.

ELECTRIC MOTOR

An electric motor is a rotating device that converts electrical energy to mechanical energy,

 Electric motor is used as an important component in electric fans, refrigerators, mixers, washing machines, computers, MP3 players etc. 

Material requirements:- 

Rectangular coil, magnetic poles , split rings. Axle, brushes and source battery.

Construction:-

An electric motor,  consists of a rectangular coil ABCD of insulated copper wire. 

The coil is placed between the two poles of a magnetic field such that the arm AB and CD are perpendicular to the direction of the magnetic field. 

The ends of the coil are connected to the two halves P and Q of a split ring. 

The inner sides of these halves are insulated and attached to an axle. 

The external conducting edges of P and Q touch two conducting stationary brushes X and Y, respectively, 

Working of electric motor:- 

Current in the coil ABCD enters from the Source battery through conducting brush X and flows back to the battery through brush Y. 

 current in arm AB of the coil flows from A to B. 

In arm CD it flows from C to D, that is, opposite to the direction of current through arm AB.

 On applying Fleming's left hand rule for the direction of force on a current-carrying conductor in a magnetic field .

 We find that the force acting on arm AB pushes it downwards while the force acting on arm CD pushes it upwards. 

Thus the coil and the axle O, mounted free to turn about an axis, rotate anti-clockwise. 

After half rotation. Q makes contact with the brush X and P with brush Y. 

Therefore the current in the coil gets reversed and flows along the path DCBA. 

A device that reverses the direction of flow of current through a circuit is called a commutator. 

In electric motors, the split ring acts as a commutator. 

The reversal of current also reverses the direction of force acting on the two arms AB and CD.

 Thus the arm AB of the coil that was earlier pushed down is now pushed up and the arm CD previously pushed up is now pushed down. 

Therefore the coil and the axle rotate half a turn more in the same direction. 

The reversing of the current is repeated at each half rotation, giving rise to a continuous rotation of the coil and to the axle.

Significance of split rings :- 

• Act as a commutator .
• Commutator is a devise that reverses the direction of flowe of current 
• Reversal of current results in a continuous rotation of coil.

The commercial motors use (i) an electromagnet in place of permanent magnet: (i) large number of turns of the conducting wire in the current carrying coil; and (iii) a soft iron core on which the coil is wound. 

The soft iron core, on which the coil is wound, plus the coils, is called an armature. This enhances the power of the motor. 

Electromagnetic induction:- Process by which changing magnetic field in a conductor induced current in another conductor.

Application:- electric generator, Wireless charger , elevators, metro trains

1. Faraday 's Experiment 1 

Observations:-

• Relative motion between magnet and coil induced electric current in the coil 

2. Faraday 's Experiment 2

Observations:- 

• Relative motion between coil induce electric current.

3. Faraday 's Experiment 3

Observations:-

• Relative motion is not an absolute requirement for inducing current.

Faraday 's  Law of induction:-

First law:- 

• An EMF is induced in circuit whenever the amount of magnetic flux (no. Of magnetic field lines per unit area) linked with a circuit changes.

Second law:- 

• Magnitude of induced EMF in a circuit is equal to time rate of change of magnetic flux through the circuit.

Methods of producing induced EMF:- 

• Varying magnetic field (B)
• Varying area(A)
• Varying relative orientation of coil and magnetic field,

Direction of induced current:-

Fleming 's right hand rule:- 

• Stretch the thumb forefinger and middle finger of right hand so that they are perpendicular to each other . If forefinger indicates the Direction of magnetic field , thumb shows the direction of motion of current then the middle finger will show the Direction of induced current. This is Fleming right hand rule.

* Electric Generator:- 

• Device that convert mechanical energy into electric energy

-Principle Based on Electromagnetic Indrection

•  It says that current is  induced in coil /loop through change in its orientation or a change in its effective area.

Types of Electric Generator :-

• AC Generator
• DC Generator

 AC Generator =

• Alternating current is produced which changes its direction after equal intervals  of time

DC Generator:- 

• Direct current is produced which does not changes its direction with time.

- Construction AC Generator:-

• Rectangular coll induced copper
• Magnetic poles
• split rings.
• Axle
• Brushes
• • Galvanometer

* working of Electric generator :- 

• When the axle attached to two rings is  rolated such that arm AB moves up & CD moves down in the magnetic Field produced by permanent magnet, It rolates the coil clockwise
• By applying Fleming's & right hand, the induced current flows in  direction ABCD
•  Thus in external circult, current flows from B₂ to B₁
• After half a rotation.arm CD starts moving up & AB moving down. 
• As a result induced current in both arms changes, giving rise to net induced current in direction DCBA
• Now in External circuit , current flows from B1 to B2.
• Thus after half a rotation, polarity of current in respective arms changes.
• such a current which changes its direction. after equal intervals of time is called alternating current
• This device is called AC Generator

Note :-If there are larger numbers of turns in  the coil, the current generated in each turn adds up to give large current through coil.

DC Generator - Working

• split ring commutator is used to ensure unidirections flow of current.
•  with this, one brush is at all times contact with arm moving down.
•  This generator is thus called a DC generator

Difference the AC & DC

• DC flows in one direction always

 •Ac flows by reverses its directions periodically

• AC Changes direction after every 1/100 sec. Frequency of AC is 50 Hz

• AC Can transmitted over  long distance without much loss of energy.

Domestic electric current:- 

• In our homes, we receive supply of electric power through a main supply (also called mains), either supported through overhead electric poles or by underground cables.
• For safe conduction , we use 3 coated wire,
•  One with red insulation cover, is called live wire (or positive).
•  Second wire, with black insulation, is called neutral wire (or negative). 
• And third with green coat called earth wire.
• In our country, the potential difference between the two is 220 V.

At the meter-board in the house, these wires pass into an electricity meter through a main fuse. 

Through the main switch they are connected to the live wires in the house. 

These wires supply electricity to separate circuits within the house. 

Often, two separate circuits are used, one of 15 A current rating for appliances with higher power ratings such as geysers, air coolers, etc. 

The other circuit is of 5 A current rating for bulbs, fans, etc. 

Functions of green wire:-

• The earth wire, which has insulation of green colour, is usually connected to a metal plate deep in the earth near the house. 
• This is used as a safety measure, especially for those appliances that have a metallic body, for example, electric press, toaster, table fan. refrigerator, etc.
•  The metallic body is connected to the earth wire, which provides a low-resistance conducting path for the current. 
• Thus, it ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, and the user may not get a severe electric shock.

Fuse:-

• Electric fuse is an important component of all domestic circuits. 
• It is a safety device which prevents the damage to appliances and the circuit due to overloading.. 
• Overloading can occur when the live wire and the neutral wire come into direct contact. (This occurs when the insulation of wires is damaged or there is a fault in the appliance.)
•  In such a situation, the current in the circuit abruptly increases. 
• This is called short-circuiting.

 The use of an electric fuse prevents the electric circuit and the appliance from a possible damage by stopping the flow of unduly high electric current. 

The Joule heating that takes place in the fuse melts it to break the electric circuit.

 Overloading can also occur due to an accidental hike in the supply voltage.

 Sometimes overloading is caused by connecting too many appliances to a single socket.

Thank you...

- 

"Bioinorganic chemistry " MSc

Bioinorganic Chemistry

• Bioinorganic chemistry is a relatively new and still growing interdisciplinary field of chemistry which largely focuses on the roles of metal ions in living systems.

Metalloporphyrins

• The metaloporphyrins are the complexes in which a metal ion is coordinated to four nitrogen atoms inside the cavity of the porphyrin ring in a square planar geometry. 
• The axial sites are available for other ligands.
•  Some examples of metalloporphyrins are hemoglobin, myoglobin, cytochromes and chlorophylls.

The porphyrin rings are the derivatives of a macrocyclic ligand called porphine.

 The porphine molecule consists of

•  unsubstituted tetra pyrole connected by methylidyne (CH) bridges.
•  These methylidyne carbon positions are labeled the alpha, beta, Gama, delta and 5, 10, 15, 20 positions in porphine and porphyrin rings respectively.
•  The 5, 10, 15, 20-tetraphenyl derivatives (tpd) are readily available because of their ease of synthesis and purification. 
• In porphyrin rings various groups are attached to the perimeter of porphine molecule.
•  The porphyrin ring can accept two hydrogen ions to form the dication (ie,+ 2 diacid) or donate two protons to form dianion.
•  In metalloporphyrin complexes the inner hydrogen atoms are replaced as protons by dipositive metal ions. 
• Therefore, the metal free porphyrin ligand has -2 charges. 
• Since, this macrocyclic ligand has a planar conjugated system of π bonds around its perimeter, it is much more rigid macrocyclic ligand than the crown ethers
•  Therefore, the ligand is more selective for certain metal atoms than the crown ethers.
•  It has a stronger preferences for the d8 Ni2+ ion. 
• The other metal ions may add above or below the square plane.
•  The structures of porphine molecule, metalloporphyrin and Fe-protoporphyrin IX or heme group are shown in Fig. 9.1.
• 
  

Fig. 9.1 Structure of (a) Porphine (b) Metalioporphynin (c) Fe-protoporphyrn DX

The porphyrin rings are rigid because of the delocalization of the π-electrons around the perimeter. 

The size of the cavity in the centre of porphyrin ring is ideal for accommodation of metal ions of the first transition series. 

If the metal ion is too small such as Ni 2+, the ring becomes ruffled to allow closer approach of nitrogen atoms to the metal ion. 

On the other hand, if the metal ion is too large, it can not fit into the cavity and occupies position above the ring which also becomes domed

Role of Iron in Living Systems

Iron is the most important transition metal involved in living systems, being vital for both plants and animals.

 In the living systems, iron has three well characterized systems:

• (1) Proteins that contain one or more porphyrin rings such as hemoglobin, myoglobin and cytochrome P450
• (2) Proteins that contain non-heme iron such as iron-sulphur compounds (ruberdoxin, ferredoxins nitrogenase)
• (3) The non-heme diiron oxo-bridged compounds such as carboxylates (hemerythrin ribonucleotide reductase and methane monooxygenase) 

Some important naturally occuring iron proteins and their functions in living systems are listed in Table 9.1.

Hemoglobin and Myoglobin

Hemoglobin contains two parts:

• heme groups and 
• globin proteins. 

A porphyrin ring containing an Fe atom is called a heme group. 

Cellular respiration is the process of using oxygen to break down glucose to produce CO₂, water and energy for use by the cell.

 It has molar mass of about 64500.

 Hemoglobin is found in red blood cells that are called erythrocytes and is resposible for their characteristic colour.

 Without hemoglobin the blood is either colourless or a different colour

 Hemoglobin picks up the weak ligand dioxygen from the lungs or gills and carries dioxygen in arterial blood to the muscles, where the oxygen is transferred to another heme containing protein, myoglobin which stores it untill oxygen is required to decompose glucose to produce energy, CO, and water 

Hemoglobin then uses certain amino and groups to bind CO, and carry it in venous blood back to the lungs

Each hemoglobin molecule is made up of four subunits, each of which consists of a globin protein in the form of folded helix or spiral. 

The globin proteins are of two types: 

• two are alpha and two are beta .

An alpha globin protein consists of 141 and an beta globin protein consists of 146 amino acids. 

Each protein consists of one polar and one non-polar group.

 In hemoglobin which has no dioxygen attached (and is therefore called as deoxyhemoglobin or reduced hemoglobin), the protein is attached to Fe(II) protoporphyrin IX through imidazole nitrogen of histidine residue in such a way that the polar groups of each protein are on the outside of the structure leaving a hydrophobic interier.

 Therefore, the heme group is held in a water resistant protein pocket.

Perutz has suggested a "trigger" mechanism for the cooperativity of the four heme groups in a process of oxygenation in hemoglobin. According to him there is a comformational change of the beme group upon coordination of an oxygen molecule which triggers interconversion of the T and R conformations. In deoryhemoglobin, iron is coordinated to four nitrogen atoms of the planar protoporphynin IX and the fifth coordination site is occupied by nitrogen atom on imidazole of a proximal histidine of globin protein. The sixth vacant site trans to the imidazole nitrogen is vacat and reserved for dicaygen. In deoxybemoglobin iron present as high spin Fe(II) with one electron ocupying the d orbital that points directly toward the nitrogen atoms of protoporphyrin DC. The presence of this electron increases the size of Fe(II) in these directions by repelling the lone pair of electrons on nitrogen atoms. As a consequence, Fe(ID becomes too large to fit easily within the hole provide by the planar protoporphyrin IX ring. The Fe() ion is, therefore, lies about 40 pm out of the plane in the direction of the histidine group, and the hese group is slightly bent into a domed shape

(Fig.9.2) The imo atom in deoxyhemoglobin has square based pyramidal coordination. The steric interactions between the histidine residue, the associated globin chain and hene group inhibit the free movement of the imm atos into the porphyrin ring Although O, is not a strong ligand, the coordination of the dioxygen molecule trami to the

histidine group as a sixth ligand ahen the strength of the ligand field and causes the pairing of electrons on iron without affecting the oxidation state of iron. Therefore, Fe(l) becomes low spin and diamagnetic. In low spin Fe(II) che six delectrons occupy the d.d. and d ochals. The darbinals is now empty and the previous effects of an electron present in this orbital in repelling the porphyrin nitrogen atoms is diminished. Therefore, the size of low spin Fell) becomes about 17 pm smaller that high spin Feil). Thus, the Fe() slips in the hole of an approximately planar porphyrin ring. As the iron slips into the hole, the midsole side chain of histidine F, al moves toward Fe atom, and the complex has an octahedral geometry Recent X-ray studies show that dioxygen is bound in a bent fashion with an Fe-0-0 angle of approximately 130. There is strong evidence for hydrogen bonding between an imidanile N-H of a distal histidine and the bound dioxygen.

the four subunits of hemoglobin are linked with each other through salt bridges between the for polypeptide chains. These salt bridges are formed mainly due to electrostatic interaction between the-NH; and-C00 groups present on all the four polypeptide chains of hemoglobin. The protein structures in hemoglobin consists of a peptide backbone with various side chains. These tide chains consist of a variety of non-polar (hydrocarboni), cationic (such as-NH;) and anionic (such -C00) groups. These salt bridges between the polypeptide chains in hemoglobin are now believed to introduce strain in the molecule. Therefore, the deoxy form of hemoglobin is called tense

state (or T state). The movement of iron atom and imidazole side chain of histidine F, toward the porphyrin plane results in breaking of some of the salt bridges. The breaking of these salt bridges reduces the strain in hemoglobin molecule. Therefore, the oxyform of hemoglobin is called relaxed state (i.e., R state). The T form of deoxyhemoglobin discourages the addition of first dioxygen molecule.

The bonding of one dioxygen molecule to a subunit of hemoglobin reduces the steric hindrance in the other subunits (due to breaking of salt bridges) and therefore encourages the bonding of dionygen molecules to the iron atom of the second subunit which in turn encourages the third as well as fourth subunits. The binding of dioxygen molecule is the most difficult in first subunit and the easiest in the last subunit due to conformational change in the protein chain (or polypeptide chain). Initial addition of a dioxygen molecule to high spin Fe(II) triggers the oxygenation of deoxyhemoglobin. This is called cooperative effect.

The phenomenon where the addition of dioxygen to one heme subunit encourages addion of the

dotypen molecules to other heme subunits is known as cooperative effect."

The successive equilibrium constants for binding of dioxygen molecules to each of the four iron

woms follow the order:

K₁ < K₂ < K₂ <K4

The fourth equilibrium constant (K) is found to be much larger than the first (K). This indicates that last O, molecule bound much more readily and tightly than the first. In the absence of conformational changes, K, would be much smaller than Ky. As a result, as soon as one or two dioxygen molecules are bound to iron atoms, all the four iron atoms are readily oxygenated. Conversely, as one O, molecule is removed from oxyhemoglobin the reverse conformational changes occur and successively decrease its affinity for oxygen. Therefore, initial removal of O, molecule from deoxyhemoglobin triggers the removal of remaining O, molecules. This phenomenon is also called as cooperative effect.

Fig. 9.3:1-oxo dimer (hematin)

The naked heme, the tron-porphyrin complex without accompanying the polypeptide chains is oxidized to Fe(III) by dioxygen molecule in aqueous solution and is converted immediately into a stableu-oxo dimer (Fig. 9.3) known as hematin. In hematin iron is high spin Fe(III). The hemarin is unable to transport oxygen. The polypeptide chain can be removed by treatment with HCl/acetone. The polypeptide chain in hemoglobin and myoglobin prevents oxidation of Fe(II) because: (1) The hydrocarbon environment round the iron has a low dielectric constant and is

hydrophobic and therefore act as a non-polar and provides non-aqueous environment.

(2) It provides steric hindrance and does not allow the formation of hematin.

The mechanism of the formation of hematin is as follows:

The first step involves the binding of the O, molecule to Fe(II) of the heme group, PFe(II)

PFe +0₂ Pre-O

Second step involves the coordination of bound oxygen to second heme group forming u peroso

complex.

+PFe"

Pre-0-0-Fe p

O Third step involves the cleavage of the peroxo complex into two ferryl complexes in which iron is present in + 4 formal oxidation state.

0. 0-Fe P-2PF-0

In the last step, the ferryl complex combines with an another heme group resulting in the formation of hematin.

Pre-O+PFeFFe-0-Fe P

Myoglobin (Mb)

Myoglobin (or deoxy-myoglobin) is a protein which has only one heme group per molecule and serves as an oxygen storage molecule in the muscles. It has molar mass of about 17000 and binds

Baterpinic Chemistry

9-7

doxygen molecule more strongly than hemoglobin. The yoglobin molecule is sindur to a single vir of hemoglobin Myoglobin is a five coordinate high spin Fell) complex with four of the ordinating positions occupied by N-atoms of the porphyrin ring. The fifth position is occupied by an Naim of an unidazole group of a histidine residue (a globin protein). The protein consists of 153 acids. This protein restricts access to the Fell) by a second heme and reduces the formation of hematin like Fe (III) dimer. The result is that the Fe(1) porphyrin complex survives long enough to nd and release dioxygen molecule. Such five coordinate heme complexes of Feill) are always high pin te with one electron occupying the da, orbital that points directly toward the four the size of Fe(II) in these directions

prpbyzn nitrogen atoms. The presence of this electron increases by repelling the lone pair of electrons of the nitrogen atoms.

The size of Fe(II) is 92 pm in the square pyramidal arrangement which is considered to be peado octahedral environment with the sixth ligand removed. The size of Fe() ia solarge that it in not fit into the hole of the planar porphyrin ring and therefore it lies about 40 pm away from the plane of the ring (Fig. 9.2). Therefore, high spin Fell) porphyrin complexes (in Hb and Mh) involves packering and twisting of porphyrin ring.

When a dioxygen molecule binds to Fe(II) at sixth coordination site trans to imidazole group of hinde residue, the complex converts to low spin Fe(1) octahedral complex and the electronic configuration changes tori (e, the six d-electrons occupy the dg. d, and, orbish leading to and da orbitals empty). The previous effect of two electrons occupying the citals in repelling the N atoms on X, Y and Z axes diminishes. Therefore, the low spin Fellt) son is maller (75 pm) and slips into the hole in the planar pophyrin ring As the Fe(10 kon moves, it pulls

beidzale group of histidine residue. Therefore, all the nitrogen atoms (including that of

painal histidine) approach more closer to the Fe(II) ion.

Physiology of Hemoglobin and Myoglobin Hemoglobin has relatively high affinity for dioxygen at high partial presure of dixygen where

The

vertibiranes diosygen enters the blood in the lungs or gills where the partial pere of dioxygen go has relatively high affauty for dioxygen at lower partial pressure of dissygen. In natively high and hemoglobin is virtually saturated with dioxygen in hurtigs When hemoglobin ramties dinnypen to muscle tissues, it experiences the lower partial pressure of dicaygen and s way for dioxygen has fallen off rapidly and in this situation affany of myoglobin for disaygen is wively high. Therefore, in muscle tissues dioxygen is thermodynamically favourable transferred han hecsoglobin to myoglobin. The reactions occuring in lungs and muscles a

Hb40,

HNO₂)

The cyproation equilibrium for myoglobin is represented as

9-8

Organometallic and Binorganic Chemistry

Mh+ O₂ Mb(0₂)

K

Iff is the fraction of myoglobin bearing oxygen and Po, is the equilibrium partial

dioxygen, then

K

K PO 1+K Pos if

pressure of

to br

or

The equilibrium constant K is called the binding constant of myoglobin for 0₂.

This is the equation for the hyperbolic curve for myoglobin (Fig. 9.4).

100

80

aope w

de

stof

hat tow

avea at

1. Th

harth his

Bohr's

The c

60

Mb

HypH-7.6 Hb pH 6.8

40+

Partial pressure of O, in lungs

Partial pressure of O, in muscle

0

20

40

60

80

100

20

Percentage satuartion with O₂

120

pure d

be Lunge

yhtey

The 1

the w

Partial pressure of O₂ in mm Hg

Fig. 9.4 Oxygen Dissociation Curves for Hemoglobin and Myoglobin. Showing how Hemoglobin is Able to Absorb O, Efficiently in the Lungs yet Transfer it to Myoglobin in Muscle Tissue

The hemoglobin curve does not follow such an equation. Hemoglobin has more complex behaviour ms it has four heme subunits. It follows an emperically modified form with Por replaced by Po

K = [Mb(0₂).]

K M

---

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"Force and Law of Motion"

 Force and law of motion

• Topics to be covered :- 
• Introducing
• What causes motion
• Force
• Balanced and unbalanced forces
• Galileo's idea of force and motion
• Newton's first law of Motion
• Newton's second law of motion
• Mass Vs inertia
• Newton's third law of motion
• Conservation of momentum

Introduction:- What causes motion?

• External force is needed to make a stationary body move 
• External force is needed to stop a moving body

Balanced and unbalanced forces:-

Balanced force:- 

• Equal and opposite forces
• Do not cause any change in motion
• Example:- Tug of war

Unbalanced forces:- 

• Unequal forces 
• Can be in the same or opposite direction
• Causes a change in motion

Law of motion:- 

• Aristotle's law of uniform motion:- An external force is required to keep a body in uniform motion.

Aristotle's fallacy:-

• He didn't discuss about opposite forces like frictional forces

Conclusion:-

• An external force is required to keep a body in motion, only if resistive forces like frictional and viscous force are present.

Galileo's Law :-

• A body moving on a frictionless surface should move with constant velocity.

Conclusion:- 

• Aristotle law was falsified by Galileo.
• A body at rest or in uniform motion experience zero net force.

Newton's first law of motion:- 

• A body at rest tends to remain at rest and a body in uniform motion tends to remain in the state of motion until and unless an external / unbalanced force is applied on it.
• Example:- Ball at rest , Ball in uniform motion

What is inertia?

• Inertia is the resistance of a body. To change its state of motion.
• Or
•  tendency of the body at rest tends to stay at rest  and tendency of the body in motion to keep in motion is called inertia.
• Example:-Jerk experienced when brakes applied suddenly.
• Tendency to bend on one side on a bike during sharp turn.

Newton's second law is about 

• Newton's first law was for scenario where net force is zero
• Newton's second law is for scenario with net force not equal to zero 

What is momentum ?.

• Momentum is product of mass of a body and it's velocity
• It is a vector quantity
• It is denoted by 'p'
• Mathematical expression is p=mv
• SI unit = kgm/s
• Dependency of force on mass 
• Force required to push object with same velocity 
• Greater the mass,more the force required to set the body in motion

Dependency of force on change in velocity

• Greater the velocity of moving object , more the force is required to stop the object
• Dependency of force on change in momentum in a  given time, greater is the force that needed to be applied.

Mathematical formulation of second law of motion:-

• Let an object of mass , m is moving along straight line with initial velocity, u
• It is uniformly accelerated to velocity, v in time t
• So initial momentum p(initial) = mu
• final momentum p(final) = mv
• Change in momentum, 
• dp = p(final) - p(initial) 
• = mv-mu = m(v-u)
• Change in momentum w.r.t time, dp/dt =m(v-u)/t
• Or, the applied force , F = km(v-u)/t = kma
• When k=1 
• F= ma 
• This is second law of motion

Newton's second law of motion:-

• The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction in which the force acts
• F  is directly proportional to (rate of change of momentum) 
• F = k(dp)/dt 
• When k=1 

• F = dp/dt

Alternatively:- 

• The relationship between an object's mass m, it's acceleration a , the applied force F is F=ma the direction of force is the same as the direction of acceleration.
• Another way of derivation :-
• F= dp/ dt

• F = d(mv)/dt
• F = m(dv)/dt
• F = ma 
• Where F= force applied,  m= mass of object , a= acceleration of an object
• Unit of force = Kgm/s^2
• S.I unit of force is newton (N)

Consistency of second law with first law:- 

• According to second law, F= ma
• If F = 0 then a=0 (m cannot be zero)

• Also acceleration is zero if the body is at rest or in uniform motion

According to first law, 

If a= 0 , F=0 

So two laws are consistent with each other.

Impulse:-

• Impulse is defined as a force multiplied by time it acts over. 
• Example :- Tennis racket striking the ball 
• Impulse = change in momentum.
• Because as per definition , I = F×t = dp

Newton's third law of motion:-

• To every action ,there is always an equal and opposite reaction
• Example:- Tonie holding ball
• He exerts force on ball to hold it - action
• The ball exert force back on his hand :- reaction
• Apple falling down the tree.
• Apple is pulled by earth due to gravitational force- action 
• Earth is pulled by Apple also - reaction 
• But mass of earth is very large as compared to Apple . So for e exerted by earth on Apple is also very large .so net force is acting on Apple and apple  down

Action and reaction forces :- 

• Action and reaction forces always act on different bodies 
• Action and reaction forces occurs at the same instant 
• There is no cause effect relation between them 

Conservation of momentum:-

• In an isolated system, the total momentum is conserved (does not mean zero) 

Example1:-

• Bullet from rifle 
• Initial momentum:- zero and kinetic energy = zero
• After fire :- momentum of bullet + momentum of rifle = zero but KE   increase
• So momentum is conserved 
• Momentum before collision = momentum after collision

English grade 6th

  Chapter 1 " Who did Patrick's homework"

1. What did Patrick think his cat was playing with? What was it really? (2)

Ans: Patrick thought that his cat was playing with a little doll. It was, in fact, a very small-sized man, an elf.

2. Why did the little man grant Patrick a wish? (2)

Ans: Patrick had saved the tiny man’s life from the cat by not handing him back to the cat. So he promised to fulfil one wish of Patrick.

3. What was Patrick’s wish? (3)

Ans: Patrick hated doing homework. His greatest wish was that the little man should do all his homework till the end of the session.

4. In what subjects did the little man need help, to do Patrick’s homework? (5, 6)

Ans: The little man needed Patrick’s help in maths, English and history.

5. How did Patrick help him? (7)

Ans: Patrick sat beside the little man and guided him. He brought books from the library and read out to him.

6. Who do you think did Patrick’s homework – the little man, or Patrick himself? Give reasons for your answer. (9, 10)

Ans: It was Patrick himself who actually did all the homework. He had to help the elf again and again with guidance and books.

A House, A Home Summary In English

Poet :- Lorraine M. Halli

A house is made of brick and stone and hard wood. It includes glass windows and very often a yard. There are a few other things also like the tiled floors, plastered walls and many doors.

However, all these things do not really make a home. It is a loving family which makes a real home. In such a family people care for each other and work unselfishly.

Chapter 2 How the Dog Found Himself

Working With the Text  (Page21)

Discuss these questions in pairs before you write the answers.

1. Why did the dog feel the need for a master? (1,2)

Ans: The dog was sick and tired of going about alone in search of food. And he did not feel safe. So he decided to have a master.

2. Who did he first choose as his master? Why did he leave that master? (3)

Ans: The dog first chose a wolf as his master. But he found the wolf afraid of the bear. So he left the company of the wolf.

3. Who did he choose next? (3)

Ans: Next, the dog chose a bear as his master, because he was stronger than the Wolf.

4. Why did he serve the Lion for a long time? (4)

Ans: The dog served the Lion for a long time because he had no complaint against him. Secondly, he felt safe and secure. No other wild animal dared to displease him.

5. Who did he finally choose as his master and why? (9, 10)

Ans: The dog finally chose a man as his master. Even the lion was afraid of man. So the dog was convinced that man was the strongest creature on earth.

B.A summary of the story is given below. Fill in the blanks to complete it taking appropriate phrases from the box. 

This is the story of___________ , who used to be___________ . He decided to find a

master___________ . First he found ______________  , but the wolf was afraid of

_________ . The dog thought that the bear was______________ . After some time the

dog met__________ who seemed the strongest. He stayed with the lion for a long

time. One day he realised that the lion was _________________  . To this day, the dog

remains man’s best friend.

Ans. This is the story of a dog, who used to be his own master. He decided to find a master, stronger than anyone else. First, he found a wolf but the wolf was afraid of the bear. The dog thought that the bear was the strongest of all. After some time the dog met a lion, who seemed the strongest. He stayed with the lion for a long time. One day he realised that the lion was afraid of man. To this day, the dog remains man’s best friend.

Poem 2

The Kite Summary In English

Poet:- Harry Behn

A new kite is wonderful to watch. Diving and dipping in the blue sky it moves its tail with a noise. It soars high with the wind. At this time it sails like a ship with only one sail. It rides on the current of air just as the ship rides on the waves of the ocean. When the wind falls it seems to rest. When the string which holds the kite goes slack, the master of the kite winds back the string. The kite comes back to the earth. It is there again in the sky when a new wind blows filling the wings of the kite with the air again.

However, when the string of the kite is caught in a tree, the kite flaps. It soon turns into a very torn and dirty thing.

Chapter 3 "Taro's Reward"

Date: 1 Sep 2021

Working With the Text    (Page 34)

A   Answer the following questions.

1. Why did Taro run in the direction of the stream? (5)

Ans: Taro ran in the direction of the stream because he was thirsty. Secondly, he had never before heard the sound of falling water in that area:

2. How did Taro’s father show his happiness after drinking sake? (7)

Ans: Sake gave warmth as well as energy to the old man. Taro’s father stopped shivering and started dancing. In this way, he showed his happiness.

3. Why did the waterfall give Taro sakeand others water? (12)

Ans: The waterfall obliged Taro and changed water into sake. The reason was that he was a thoughtful son. He served his old parents sincerely. Sake was the reward for his goodness. Other people were just greedy. So they got only plain water.

4. Why did the villagers want to drown Taro? (10, 11)

Ans: The villagers went to the waterfall to collect sake. But they got only plain cold water. They thought that Taro had tricked them. So they looked for Taro to punish him.

5. Why did the Emperor reward Taro? (13)

Ans: The Emperor of Japan rewarded Taro for being good and kind towards his parents. This was Emperor’s way to encourage all children to respect, obey and serve their parents.

B. Mark the right item.

1. Taro earned very little money because

(i)he didn’t work hard enough.

(ii)the villagers didn’t need wood.

(iii)the price of wood was very low.

2.Taro decided to earn extra money

(i)to live a more comfortable life.

(ii)to buy his old father some sake.

(iii)to repair the cracks in the hut.

3. The neighbour left Taro’s hut in a hurry because

(i)she was delighted with the drink.

(ii)she was astonished to hear Taro’s story.

(iii)she wanted to tell the whole village about the waterfall.

Ans. 1. (iii), 2. (ii), 3. (iii)

The Quarrel Summary In English

Poet ;- Eleanor Farjeon

The poet quarrelled with his brother on some very petty matter. It was so petty that now he does not remember what it was. One thing led to another. Both of them felt that they were right. It had started as something small. It had become big in the end. So they began to hate each other. The afternoon became very tense and unpleasant for both of them.

Then suddenly, the poet’s brother patted him on the back. He said that the two of them could not go along like that for a long time. It would be difficult to pass the night in that manner. He said that it was his mistake, Just then the poet felt that his brother was right. In fact he himself was wrong.

Chap 4 An Indian Woman. In Space : Kalpana Chawla

Answer the following questions.

1. Where was Kalpana Chawla born? Why is she called an Indian-American? (3)

Ans: Kalpana Chawla was born at Kamal, in Haryana. She was born in India, but married an American and became a naturalised citizen. So she is called an Indian- American.

2. When and why did she go to the U.S? Who did she marry? (2, 3)

Ans: Kalpana went to the U.S. for higher studies in aeronautical engineering. There she married the flight instructor Harrison.

3.How did she become an astronaut? What gave her the idea that she could be an astronaut? (3)

Ans: Kalpana had already got a bachelor’s degree in aeronautical engineering before she went to the U.S. She earned her PhD in aerospace engineering. In 1994 she was selected by NASA for training as an astronaut. She was encouraged by the people around her.

4. What abilities must an astronaut have, according to the journalist? (6)

Ans: An astronaut needs to know a lot about biology and aeronautical engineering. He/ she must have a wide knowledge of science subjects.

 5. Describe Kalpana Chawla’s first mission in space. (5)

Ans:  Kalpana’s first mission in the space shuttle, Columbia, was nearly 16 days long. She went around the earth 252 times. Among her colleagues were a Japanese and Ukranian astronauts. They performed so many experiments.

6. What does Kalpana Chawla say about pursuing a dream? Do you agree with her that success is possible? (7)

Ans:  Kalpana Chawla, a girl from a small town, touched the skies. In her message to college students of Chandigarh, from space, she said that it was always possible to realise one’s dream. One could certainly get success provided one had the vision and the courage.

B. Read the newspaper report to find the following facts about the Columbia’s ill- fated voyage.

1. Date and place of lift off:_____________________________________________________

2. Number of astronauts on board:_______________________________________________

3. Number of days it stayed in space:_____________________________________________

4. Number of experiments done by scientists:_______________________________________

5. Date of return journey: ______________________________________________________

6. Height at which it lost contact:_________________________________________________

Ans:

1 .16 January 2003                

2. Seven

3 .About 16 days eighty experiments

4 .1 February 2003 6. 200,000 feet

Beauty Poem Summary

The poet is trying to say in this poem that beauty is in everything. All the small things we do or the environment around us, everything has beauty in it. Everything has its own importance. All things are beautiful in their own unique way. Sunlight has its own beauty. Beauty can be seen in the growing corns, people who are working and dancing for getting good harvest. Beauty is not only seen but can also be heard or felt. For instance, when night falls, wind blows slowly, the sound of rainfall, or when a singer sings. They all give pleasure to the mind and make it feel happy.Beauty is not just outside, it is within. Beautiful is the self. Our good deeds, happy thoughts please everyone are all beautiful.Our dreams are also beautiful as they give us reason to advance and work with zeal. Beauty is in your style of work, the way you take rest and sleep.Beauty is everywhere. It is in attitude, the way we look at things. Actually everything is beautiful in its own unique manner, the need is to feel it.

Chapter 5 A Different Kind of School

 Working With the Text  (Page 62)

A. Put these sentences from the story in the right order and write them out in a paragraph. Don’t refer to the text.

I shall be so glad when today is over.

Having a leg tied up and hopping about on a crutch is almost fun, I guess.

I don’t think I’ll mind being deaf for a day—at least not much.

But being blind is so frightening.

Only you must tell me about things.

Let’s go for a little walk.

The other bad days can’t be half as bad as this.

Ans: Let’s go for a little walk. Only you must tell me about things. I shall be so glad when today is over. The other bad days can’t be half as bad as this. Having a leg tied up and hopping about on a crutch is almost fun, I guess. I don’t think I’ll mind being deaf for a day, at least not much. But being blind is so frightening.

B. Answer the following questions:

1. Why do you think the writer visited Miss Beam’s school? (1)
Ans: The writer had heard much about Miss Beam’s new teaching method. So he visited her school to see the new play-way method personally.

2. What was the ‘game’ that every child in the school had to play? (9)
Ans: Every child in the school had to play the role of being blind, deaf, dumb, injured and lame once in a term. It was a sort of game and training.

3. “Each term every child has one blind day, one lame day …”. Complete the line. Which day was the hardest? Why was it the hardest? (9, 11, 15)
Ans:  “… one injured day and one dumb day.” Being blind was the hardest day. The student felt that he/she was going to be hit by something every moment.

4. What was the purpose of these special days? (5, 9)
Ans: The purpose of these special days was to give the children a personal taste of misfortune. They learnt to help the needy in society. Such training made them good citizens.

Pact with the sun 

Chapter 1

Date: 5 Sep 2021

1. How did the two baby-birds get separated?

Ans: The two baby birds lived in a tall tree with their mother. One day a big storm blew. The tree came down. The mother bird was killed. The strong wind blew the two chicks away to the other side of the forest at a little distance from each other. Thus they got separated from each other.

2.Where did each of them find a home?

Ans: One of the young birds came down near a cave. A gang of robbers lived there. The other bird landed outside the ashram of a rishi at a little distance.

3.What did the first bird say to the stranger?

Ans: The first bird saw the stranger (the King). He called the robbers to hurry up and rob the man of his jewels and his horse. Indirectly he asked the stranger to leave the place at once.

4. What did the second bird say to him?

Ans: The second bird welcomed the king to the ashram. He requested the stranger to drink water, take rest and make himself comfortable. He added that his brother lived in the company of robbers, so he talked like them.

5.’ How did the rishiexplain the different ways in which the two birds behaved?

Ans: The king told the rishi about the different behaviour of the two birds. The rishi explained that the first bird repeated the words of the robbers. The second bird repeated what he had always heard at the ashram. Their different ways were the results of their company.

6. Which one of the following sums up the story best?

(i) A bird in hand is worth two in the bush.

(ii)One is known by the company one keeps.

(iii)A friend in need is a friend indeed.

Ans: (ii) One is known by the company one keeps.

Chapter 2 The Friendly Mongoose

1. Why did the farmer bring a baby mongoose into the house?

Ans: The farmer had a small son. He wanted to have a pet to give company to his child. So he brought home a baby mongoose to play with the child.

2. Why didn’t the farmer’s wife want to leave the baby alone with the mongoose?

Ans:The farmer’s wife did not trust even her pet mongoose. She did n’t want to leave her son alone with an animal.

3. What was the farmer’s comment on his wife’s fears?

Ans: The farmer understood why his wife was afraid of leaving the baby alone with the mongoose. Therefore, he tried to remove her fear. He said that the mongoose was a friendly animal, as sweet and gentle as their own baby.

4. Why did the farmer’s wife strike the mongoose with her basket?

Ans: The farmer’s wife returned home with a heavy basket. She noticed blood on the face and paws of the mongoose. She had no doubt that the mongoose had killed her son. So in anger she hit the animal with the basket. The poor mongoose died on the spot.

5. Did she repent her hasty action? How does she show her repentance?

Ans: The farmer’s wife saw the snake tom into pieces. Her own son was safely asleep. She realised her mistake. She felt very sorry. She touched the mongoose and cried. She saw the painful result of her hasty action.

Chapter 3 The Shepherd’s Treasure

1. The shepherd had n’t been to school because

(i)he was very poor.

(ii)there were very few schools in those days.

(iii)he wasn’t interested in studies.

Choose the right answer.

Ans: (ii) There were very few schools in those days.

2.Who visited the shepherd one day. and why?

Ans:  The shepherd soon became famous for his wisdom and friendly nature. The king of Iran heard about him and visited him. He was riding a mule and dressed like a shepherd.

3.Why did the other governors grow jealous of the shepherd?

Ans: The common shepherd was appointed the governor of a small district. He was loved and honoured by the people. His fame spread far and wide. So the governors of other provinces grew jealous of him.

4.Why was the new governor called to the palace?

Ans: The jealous governors poisoned the king’s ears against the new shepherd-governor. They reported that the new governor was dishonest, and he always carried his ill-gotten treasure in an iron chest. So the king called him to the palace to see that treasure.

5. Why was everyone delighted to see the iron chest on the camel’s back?

Ans: Those who were present in the palace, thought that the iron-box contained valuables. If their report proved true, the king would dismiss the shepherd. So they were delighted. They waited anxiously to see the contents of the box.

6. (i) What did the iron chest contain?

(ii)Why did the shepherd always carry it?

(iii)Is it an example of the shepherd’s humility or wisdom or both?

Ans: (i) The iron chest contained only an old blanket.

(ii)The shepherd always carried his blanket in the box because it was his oldest and time-tested friend. It would protect him in case the king took away his post and power.

(iii)Yes, it is an example of the shepherd’s humility as well as wisdom.

7. How did the king reward the new governor?

Ans:The king was highly pleased with the new governor’s humility and honesty. He rewarded him with a promotion. He made him the governor of a much bigger province the same day.

Chapter 4 The Old-Clock Shop

1. What made Ray think the visitor was not really a shopper?

Ans: Ray was deaf and dumb, but a good judge of men. His old wise eyes told him that the new visitors to his shop at that late hour, was not a shopper or customer. There was no friendliness in his eyes.

2. Why do you think he had come to the shop?

Ans: The visitor had not come to the shop to buy anything. Perhaps his intention was to loot the owner of his cash. He was in dire need of money.

. How did Ray communicate with him?

Ans: Ray could neither speak nor hear. So he communicated with his customer by writing his message on a notepad. The visitor also wrote his reply on paper.

4. What do you think the man said to his friend who waited at the door?

Ans: The older man pointed to his ears and shook his head from side to side. Thus he conveyed to his younger companion that the shop owner could neither hear ‘ nor speak.

5. Raypeople in exchange for their old watches and clocks?

Ans: Ray was not a pawnbroker, a person who lends money on security of some item. He did not lend money on interest. He was, however, kind and helpful. He could n’t say ‘No’ to the needy people.

6. “The watch was nothing special and yet had great powers.” In what sense did it have ‘great powers’?

Ans: The watch was just ordinary. But it had the power to pull a person out of a bad situation. The older man got the money he needed without hurting Ray. The generous shopkeeper also escaped physical injury. In this sense the watch had great powers.

7. Do you think the man would ever come back to pick up the watch?

Ans:No, it is very unlikely that the older man would ever come back to pick up his watch. He had, after all, got a price higher than the watch was worth for.

8. When did “the unfriendly face” of the visitor turn truly friendly?

Ans: The unfriendly face of the visitor turned friendly when he got a fifty dollar note for his ordinary watch. He felt obliged and happy.

.