Biomolecules

Biochemistry

1. B I O M O L E C U L E S By: Mr. Tushar P. Dukre Assistant Professor SSSIOP, Malwadi, Bota.

2. Biomolecules are the compounds needed for life. Biomolecules are the molecules present in a living organism. These biomolecules are fundamental building blocks of living organisms as they support the biological processes essential for life. E.g. carbohydrates, proteins, nucleic acids, lipids, vitamins, etc. The principle organic constituents in a living cell are as following: Introduction

3. Most of them are organic compounds. Functional group determines their chemical properties. Most biomolecules are asymmetric. Building block molecules have simple structure. Biomolecules first grow by chemical evolution. Characteristics of Biomolecules:

4. These are the compounds of carbon, hydrogen and oxygen. On hydrolysis, they yield simple sugar. Sugars are aldehyde or ketone derivatives of polyhydric alcohols i.e. Glycerol (-OH = alcohol group) Glyceric aldehyde (-CHO = aldehyde group), Dihydroxyl acetone (-CO = ketone group) Carbohydrate:

5. Monosaccharides , disaccharides and polysaccharides are all carbohydrates, but the most important carbohydrate in nature is dextrose (glucose). All carbohydrates are converted in to it before oxidation in tissues. Carbohydrate:

6. These are the neutral fats, oils and waxes and just like carbohydrates lipids are compounds of carbon, hydrogen and oxygen. They occur in plant and animal tissues and are insoluble in water, but are soluble in organic solvents like chloroform, benzene, ether, alcohol, etc. Lipids:

7. These are complex nitrogenous compounds of carbon, hydrogen, oxygen and nitrogen. Sometimes they may also contain other elements like sulphur, phosphorus, iron, etc. They have high molecular weight and on hydrolysis i.e. on decomposition of reaction with water, they form amino acids. Proteins:

8. An amino acid, is an organic compound which contains amino ( NH2 ) group and a carboxyl ( -COOH ) group. Glycerine is the simplest amino acid. 20 different amino acids have been isolated from different proteins. Proteins:

9. These are the largest and the most fascinating molecules found in living matter. These are the carriers and mediators of genetic information from one generation to another and exert primary control over basic life processes in all organisms. Like proteins, nucleic acids are also polymers. Nucleic acids :

10. Chemical Nature And Biological Role

11. Carbohydrate are defined as polyhydroxyalcohols with aldehydes and ketones and their derivatives. These are widely distributed both in animal and plant tissues. In animals, carbohydrates in the form of glucose and glycogen serve as an important source of energy. Some carbohydrates have highly specific functions; E.g. ribose and deoxyribose are carbohydrates which are components of nucleoproteins. A. Carbohydrate:

12. A. Carbohydrate: (Classification)

13. A. Carbohydrate: (Classification) Carbohydrate are divided into four major types: Monosaccharide's : These are often called as simple sugars. Which cannot be hydrolysed into a simpler form. The general formula is C n (H 2 O) n . They can be further sub-divided as shown in above table.

14. A. Carbohydrate: (Classification) Sr. No. Carbon atoms (No) Aldoses : Examples Ketoses : Examples 1. Trioses (3) Glyceraldehydes or glycerose Dihydroxyacetone 2. Tetroses (4) Erythrose Erythrulose 3. Pentoses (5) Ribose, xylose , arabinose Ribulose , xylulose 4. Hexoses (6) Glucose, galactose, mannose Fructose 5. Heptoses (7) Glucoheptose , galactoheptose Sedoheptulose

15. A. Carbohydrate: (Classification) Disaccharides: These carbohydrates produce two molecules of the same or different monosaccharide's on hydrolysis. The general formula is C n (H 2 O) n – 1 . Examples: Lactose, Maltose, Sucrose. Oligosaccharides: These carbohydrate yield 2-10 monosaccharide unit on hydrolysis, E.g. Maltotriose .

16. A. Carbohydrate: (Classification) Polysaccharides: These carbohydrates yield more than ten molecules of monosaccharide’s on hydrolysis. The general formula is (C 6 H 10 O 5 ) n . Sub-class: Homo-polysaccharide’s : Starch, glycogen, cellulose, dextrin. Hetero-polysaccharide’s: Mucopolysaccharides .

17. Asymmetric Carbon Atom: A carbon atom to which four different atoms or groups of atoms are attached is said to be asymmetric carbon atom. Many biochemical's contain two or more asymmetric carbon atoms. The presence of asymmetric carbon atom allows formation of isomers. The compounds which have the same structural formula, but differ only in spatial configuration are called as stereo – isomers or geometric isomers.

18. Classification of Isomers: Isomers of carbohydrates are classified as under: D and L isomer : The designation of an isomer as D- or L- form is determined by spatial configuration to the parent compound. When –OH group around the carbon atom at right side, the sugar belongs to D-series. If the –OH group is on left side, it is a member of L-series.

19. Classification of Isomers: Optical isomer: When a beam of polarised light passed through a solution exhibiting optical activity, it will be rotated to right or left in accordance with presence of optical isomer. A compound which causes rotation of polarised light to the right is said to be dextro-rotatory and is designated with plus (+) sign. Rotation of beam to the left is termed as leavo-rotatory and is designated with minus (-) sign.

20. Classification of Isomers: Epimer: Isomers formed as a result of interchange of –OH and –H on carbon atoms 2, 3 and 4 of glucose are known as epimers. In the body, epimerisation take place by the enzyme epimerase. Biologically, most important epimers of glucose are mannose and galactose formed by epimerisation at carbon 2 and 4 respectively.

21. Classification of Isomers: Anomer ( α and β ): The cyclic structure of glucose is retained in solution, but isomerism takes place about position 1. This is accomplished by optical rotation (mutarotation) by which the position of –H and –OH groups are changed around carbon 1. Inter-conversion of α and β glucose in solution with change of optical activity is called mutarotation.

22. Classification of Isomers: Pyranose and Furanose: All sugars forming six membered rings are called as pyranoses and those forming five membered rings are called as furanoses. Amylene oxide form of glucose = glucopyranose . Butylene oxide form of glucose = glucofuranose .

23. Classification of Isomers: Aldose and Ketose: Fructose has same molecular formula as that of glucose but differs in its structural formula since carbon-2 is a part of CO group, which make fructose a ketose sugar rather than aldose . Structure of β -D-Fructose

24. Physiological Significance of Carbohydrate

25. MONOSACCHARIDE'S : Sr. No. Sugar Source Physiological importance 1. D-Ribose Nucleic acid Structural elements of nucleic acids and coenzymes, e.g. ATP, NAD, NADOP, FAD. 2. D- Ribulose In metabolic processes Intermediates in hexosemonophosphate shunt. 3. D- Arabinose Plum and cherry gums Bacterial metabolism 4. D- Xylose Wood gums Bacterial metabolism 5. D- Lyxose Heart muscle Component of lyxoflavin isolated from human heart muscle. Physiological importance of some Pentose

26. MONOSACCHARIDE'S : Sr. No. Sugar Source Physiological importance 1. D-Glucose Fruit juice, cane sugar, maltose, lactose, etc. Carried by blood and used by tissues. Presence in urine is called glycosuria . 2. D-Fructose Fruit juice, honey. Hydrolysis of cane sugar. Changed to glucose in liver and intestine and thus used in body. 3. D-Galactose Hydrolysis of lactose. Changed to glucose in liver and metabolised . 4. D-Mannose Hydrolysis of plant mannosans and gums Constituents of prosthetic polysccharides of albumins, globulins, mucoproteins . Physiological importance of some Hexoses

27. MONOSACCHARIDE'S : Glycosides: These are the compounds formed by consideration between a sugar and the hydroxyl group of second compound called aglycone which may or may not be another sugar. Physiological importance: Glycosides are found in many drugs, spices and animal tissues. Cardiac glycosides, e.g. digitalis contain steroids as aglycone. Other glycosides include antibiotics like streptomycin.

28. MONOSACCHARIDE'S : Amino sugar ( Hexosamines ): Sugar containing amino group are called as amino sugar; e.g. D- galactosamine , D-glucosamine, D- mannosamine . Physiological importance: Glucosamine is a component of hyaluronic acid. Galactosamine is a consituents of glycoproteins. Mannosamine is an important constituent of mucoprotein . Several antibiotics like erythromycin, carbomycin contain amino sugars.

29. DISACCHARIDE'S : Physiological importance Maltose (Malt sugar): It does not occur in the body. It is present in germinating cereals and malt. It is the intermediate product in the breakdown of starch by amylase in the alimentary tract. Lactose (Milk sugar): It is present in milk and formed in lactating mammary glands. It may occur in urine during pregnancy. Sucrose (Cane sugar): It occurs in cane sugar, pineapple, carrot roots, sweet potato and honey. It is hydrolysed to glucose and fructose by sucrase in the alimentary canal and product are absorbed.

30. POLYSACCHARIDE'S : Physiological importance Cellulose: It is the main constituents of supporting tissues of plants and forms a considerable part of vegetable food. It does not occurs in animal. It is not acted upon by amylase in digestive system. Glycogen (Animal starch): It is the reserved carbohydrate found in liver and muscle of animals and human beings. The glycogen content of liver is more than that of muscle. It is also found in plants which have no chlorophyll system; e.g. fungi and yeast. Not present in green plants.

31. POLYSACCHARIDE'S : Physiological importance Starch: It is the store of carbohydrate in green plants. Most important source of carbohydrate in our food and found in potatoes, legumes, and other vegetable in high concentrations. It is a mixture of two substances: amylase and amylopectin. Dextrin's: Dextrin’s are formed by partial hydrolysis of starch by an enzyme, salivary amylase, dilute mineral acids or heats. Have faint sweet taste.

32. B. LIPIDS: The lipids are heterogenous compounds related to fatty acids. They are insoluble in water and soluble in organic solvents like ether, chloroform and benzene. Chemically they are esters of fatty acids and alcohols.

33. Biological Significance of Lipids : Lipids (fats) serves as an efficient source of energy. They are stored in adipose tissue. The fat-soluble vitamins and essential fatty acids are found with the fat of natural food. Serve as an insulating material in the sub-cutaneous tissues and around certain organs. Lipoproteins (combinations of fat and protein) and glycolipids (combinations of fat and carbohydrate) are essential for maintaining cellular integrity. Provide building blocks for different high molecular weight substance, e.g. acetic acid can be used for synthesis of cholesterol.

34. Classification of Lipids :

35. 1. Simple Lipids: Simple lipids are further sub-classified as fat and waxes. Fats: They are esters of fatty acids with glycerol. They are the best reserves of food material in human body. Acts as insulator for the loss of body heat. Acts as padding material for protecting internal organs. The chemical structure of fat consists of three different molecules of fatty acids (R1, R2, R3) esterified with three hydroxyl groups of glycerol.

36. 1. Simple Lipids: Fats: Structure of Fats (Triglycerides)

37. 1. Simple Lipids: Fats: Fats are characterised by following parameters: Saponification number: It is defined as the number of mgs of KOH required to saponify 1 gm of fat or oil. It is depends on number of –COOH groups present on the fat/oil. Fat containing short chain fatty acids will have more –COOH groups and will have higher saponification number. Acid number: Defined as number of mgs of KOH required to neutralise free fatty acids of 1 gm of fat. The acid number indicates degree of rancidity of the given fat.

38. 1. Simple Lipids: Fats: Fats are characterised by following parameters: Iodine number: It is the amount (in gms ) of iodine absorbed by 100 gm of fat. It is the measure of degree of unsaturation of fat. Highly unsaturated fatty acids will have higher iodine number. Acetyl number: It is the number of mgs of KOH required to neutralise the acetic acid obtained by saponification of 1 gm of fat after it has been acetylated.

39. 1. Simple Lipids: Fats: Fats are characterised by following parameters: Polenske number: It is the number of ml of 0.1 N KOH required to neutralise the insoluble fatty acids from 5 gm of fat. Wollny number: It is the same as Polenske number except that the soluble fatty acids are measured by titration of the distillate obtained by steam distillation of the saponification mixture. It indicates how much volatile fatty acid can be extracted from fat through saponification.

40. 1. Simple Lipids: Waxes: Waxes are esters of fatty acids with higher alcohols other than glycerol. In human body, commonest waxes are esters of cholesterol. They are of three: True waxes are esters of higher fatty acids with acetyl alcohol or other higher straight chain alcohols. Cholesterol esters are esters of fatty acid with cholesterol. Vitamin A and vitamin D are palmitic / stearic acid esters of vitamin A (Retinol) or vitamin D respectively.

41. 2. Compound Lipids: They are esters of fatty acids containing groups in addition to an alcohol and a fatty acid. They are further sub-classified as: Phospholipids ( phosphatides ): They are esters of fatty acids with glycerol containing as esterified phosphoric acid and a nitrogen base. They are present in large quantity in nerve tissue, brain, liver, kidney, pancreas and heart.

42. 2. Compound Lipids: Phospholipids ( phosphatides ): Biological importance: They increase the rate of fatty acid oxidation. They act as carriers of inorganic ions across the membrane. They help in blood clotting. They act as prosthetic group to certain enzymes. They form the structures of membranes, matrix of cell wall, myelin sheath, microsomes and mitochondria.

43. 2. Compound Lipids: Phospholipids ( phosphatides ): Phospholipids are further sub-classified as: Glycerophosphatides : In this type of phospholipids, glycerol is the alcohol group. Example : Phosphatidic acid, Lecethin , Cephalin .

44. 2. Compound Lipids: Phospholipids ( phosphatides ): Phospholipids are further sub-classified as: Phosphoinositides : In this type, inositol is the alcohol. Example : Phosphatidyl inositol ( Lipositol ).

45. 2. Compound Lipids: Phospholipids ( phosphatides ): Phospholipids are further sub-classified as: Phosphosphingosides : In this type, sphingosine is an amino alcohol. Example : Sphingomyelin .

46. 2. Compound Lipids: Phospholipids ( phosphatides ): Clinical importance of phospholipids: In Niemann -Pick disease, excess amount of sphingomyelin are deposited in brain, liver and spleen. It is due to deficiency of enzyme sphingomyelinase . The symptoms are: enlarged liver and spleen, mental retardation, anaemia and leucocytosis .

47. 2. Compound Lipids: Glycolipids: These lipids contain amino alcohol (sphingosine or iso-shingoshine ) attached with an amide linkage to a fatty acid and glycosidically to a carbohydrate group (sugars, amino acid, sialic acid), they are further sub-classified as follows: Cerebrosides Gangliosides Sulpholipids Amino lipids

48. 2. Compound Lipids: Glycolipids: S ub-classified as follows: Cerebrosides : They contain galactose, a high molecular weight fatty and sphingosine. They are chief constituent of myelin sheath. Cerebrosides are in much higher concentration in medullated rather than in non- medullated nerve fibres. E.g. Kerasin , Cerebron . Clinical importance: In Gaucher’s disease, cerebroside content of reticuloendothelial cell (spleen) is very high. It is caused by deficiency of enzyme glucocerebrosidase . Symptoms: Increase in size of spleen, leucopenia, liver enlargement.

49. 2. Compound Lipids: Glycolipids: S ub-classified as follows: Gangliosides : They are glycolipids occuring in the brain. They contain ceramide (sphingosine + fatty acid), glucose, galactose and sialic acid. There are three types of gangliosides : GM1, GM2 and GM3. GM1 is due to deficiency of enzyme β - galactosidase . GM2 termed as Tay Sach’s disease, caused due to deficiency of enzyme hexosaminidase . Symptoms : mental retardation, blindness and muscular weakness.

50. 2. Compound Lipids: Glycolipids: S ub-classified as follows: Sulpholipids ( sulphatides ): These have been isolated from brain and other animal tissues. These are sulphate derivatives of the galactosyl reduce in cerebrosides . Amino lipids: Phosphatidyl ethanoamine and serines are amino lipids and sphingomyelins , gangliosides contain substituted amino groups.

51. 2. Compound Lipids: Glycolipids: S ub-classified as follows: Sulpholipids ( sulphatides ): These have been isolated from brain and other animal tissues. These are sulphate derivatives of the galactosyl reduce in cerebrosides . Amino lipids: Phosphatidyl ethanoamine and serines are amino lipids and sphingomyelins , gamgliosides contain substituted amino groups.

52. 2. Compound Lipids: Lipoproteins: Characteristics: To form a hydrophilic lipoprotein complex, there should be a combination of triacylglycerol (45%), phospholipids (35%), cholesterol and cholesteryl esters (15%), free fatty acids (<5%) and protein. The density of lipoprotein increases as the protein content rises and the lipid content falls and the size of the particle becomes smaller. Four major group of lipoproteins have been identified. They are physiologically important. They used in clinical diagnosis is some metabolic disorders of fat metabolism.

53. 2. Compound Lipids: Lipoproteins: Four sub-types are as follows: Chylomicrons : Both chylomicrons and VLDL contain triacyl glycerol (50%) and cholesterol (23%) as predominant lipids. Their concentration is increased in atherosclerosis and coronary thrombosis. Very low density lipoproteins (VLDL/pre- β -lipoproteins): It is assembled in the liver from triglycerides, cholesterol and apolipoproteins .

54. 2. Compound Lipids: Lipoproteins: Four sub-types are as follows: Low density lipoproteins (LDL/ β -lipoproteins): Predominant lipid in LDL is cholesterol (46%) and phospholipids (23%). It is increased in atherosclerosis, coronary thrombosis. High density lipoproteins (HDL/ α -lipoproteins): Predominant lipid in HDL is phospholipid (27%) and proteins (>45%)

55. 2. Compound Lipids: Lipoproteins: Physiological Importance: To transport and deliver the lipids to tissues. To maintain structural integrity of cell surface and sub-cellular particles like mitochondria and microsomes. The β -lipoproteins fraction increases in severe diabetes mellitus and atherosclerosis.

56. 3. Derived Lipids: They are classified in to two categories: fatty acid and steroids. Fatty acids: These are obtained by hydrolysis of fats. Fatty acids occuring in natural fats usually contain an even number of carbon atoms. Usually they are straight chain derivatives. The straight chain may be either saturated or unsaturated. In addition, there are few fatty acids which are typical.

57. 3. Derived Lipids: Saturated Fatty acids: General formula for saturated fatty acid is CnH2n+1COOH . Sr. No. Name of acid Formula Number of carbon atoms 1. Acetic CH 3 COOH 2 2. Propionic C 2 H 5 COOH 3 3. Butyric C 3 H 7 COOH 4 4. Capronic C 5 H 11 COOH 6 5. Caprylic C 7 H 15 COOH 8 6. Decanoic ( Capric ) C 9 H 19 COOH 10 7. Lauric C 11 H 23 COOH 12 8. Myristic C 13 H 27 COOH 14 9. Palmitic C 15 H 31 COOH 16 10. Stearic C 17 H 35 COOH 18 11. Arachidic C 19 H 39 COOH 20 12. Behenic C 21 H 43 COOH 22 13. Lignoceric C 23 H 47 COOH 24

58. 3. Derived Lipids: Unsaturated fatty acids: Unsaturated fatty acids are classified as mono-unsaturated fatty acid (MUFA) and poly-unsaturated fatty acid (PUFA). Sr. No. Type of acid Name of acid Formula Number of carbon atoms 1. Mono-unsaturated Palmitoleic C 15 H 29 COOH 1 2. Mono-unsaturated Oleic C 17 H 33 COOH 1 3. Poly-unsaturated Linoleic C 17 H 31 COOH 2 4. Poly-unsaturated Linolenic C 17 H 29 COOH 3 5. Poly-unsaturated Arachidonic C 19 H 31 COOH 4 Eicosanoids 6. Protanoids Timmoionic C 19 H 33 COOH 5 7. Leukotrienes Clupanodonic C 12 H 32 COOH 5 8. Leukotrienes Cervonic C 21 H 31 COOH 6

59. 3. Derived Lipids: Unsaturated fatty acids: Prostanoids (PUFA) are subclass of eicosanoids which are further sub-divided as Prostaglandins (PG) and Thromboxanes (TX) and Prostacyclins (PGI2) General characteristics of prostanoids are as follows: All are having 20 carbon compounds. Trans double bond is at 13 position. -OH group is at 15 position.

60. 3. Derived Lipids: Unsaturated fatty acids: Classification of Prostanoid and Leukotriene .

61. 3. Derived Lipids: Unsaturated fatty acids: Prostaglandins (PG): They exist in almost every mammalian tissue and act as local hormones. They have important physiological and pharmacological activities. They are obtained from arachidonic acid to form a cyclopentane ring. PGE2

62. 3. Derived Lipids: Unsaturated fatty acids: Thromboxanes (TX): They contract smooth muscles on blood vessels, GI tract, uterus and bronchioles. They are located in platelets, and have the cyclopentane ring interupted with an oxygen atom (oxygen ring). TXA2

63. 3. Derived Lipids: Unsaturated fatty acids: Leukotrienes : They are third group of eicosanoid derivatives formed by the lipooxygenase pathway. They are located in leucocytes and are characterised by the presence of three conjugated double bonds. Forth double bond in LTA4 is not conjugated. LTA4

64. 3. Derived Lipids: Essential Fatty Acids: Fatty acids which are essential for growth and health of humans and other animals have been termed as essential fatty acids. They are poly-unsaturated fatty acids which are not synthesized in the body, but are taken form natural sources. Examples: Linoleic acid, Linolenic acid, arachidonic acid. They have low melting points and iodine number.

65. 3. Derived Lipids: Essential Fatty Acids: Physiological importance of essential fatty acids: They are structural constituents of the cell. They cause prolongation of clotting and increase hydrolytic activity. They cure skin lesions. Their deficiency in diet of babies causes eczema.

66. 3. Derived Lipids: Steroids: Steroids are often found in association with fat. They have a cyclic nucleus resembling phenanthrene (ring A,B,C) to which a cyclopentane ring (D) is attached. The structure and nomeclature for numbering of carbon atoms is shown in Fig. Methyl side chains occurs at positions 10 and 13. A side chain at position 17 is usual. If the compound has one or more hydroxyl groups and no carbonyl or carboxyl groups, is called as sterol.

67. 3. Derived Lipids: Steroids: Steroids are divided in following manner: Sterols : Cholesterol, ergosterol , coprosterol . Bile acids: Glycocholic acid, taurocholic acid. Sex hormones: Testosterone, estradiol . Vitamin D: Vitamin D2 and D3. Adrenocortico hormone: Corticosterone , hydroxyl corticosterone . Cardiac glycosides: Stropanthin . Saponins: Digitonin , digitoxin .

68. C. Nucleic Acids: Nucleic acids are made up of nucleotides. Nucleotides are composed of purine or pyrimidine bases, ribose or deoxyribose sugars and phosphoric acid. When phosphoric acid from a nucleotide is removed, the remainder part is termed as nucleoside. Thus a nucleoside is composed of a purine or pyrimidine base and a ribose or a deoxyribose sugar.

69. C. Nucleic Acids: The nomenclature indicating numbers to carbon/nitrogen atoms of purine and pyrimidine are indicated below: Structure and nomenclature of Purine and Pyrimidine

70. C. Nucleic Acids: Biological importance of Nucleotides: Nucleotides are important intracellular molecules of low molecular weight. They play an important role in carbohydrate, fat and protein metabolism. The most important role of nucleotides is of being precursors of DNA and RNA. The purine nucleotides also act as the high energy source ATP, cAMP in a wide variety of tissues and organisms. The pyrimidine nucleotides also act as high energy intermediates such as UDP-glucose and UDP-galactose in carbohydrate metabolism.

71. D. Amino Acid and Proteins: Proteins are made up of amino acids. An intermediate stage between amino acids and proteins is of peptides. Hence some basic information on amino acids and peptides is essential. Although there are 200 amino acids found in nature, only 20 of them occur in proteins. The general structure of an amino acid is

72. D. Amino Acid: Common Properties of Amino Acids: Amino acids have at least two ionisable groups i.e. –COOH and –NH3 + . Carboxyl group dissociates more easily than amino group. In solution, two forms of these group, one charged and one neutral, exist in protonic equilibrium with each other. R-COOH R-COO - + H+ and R-NH3 + H + + R-NH2 R-COOH and R-NH3+ represent the protonated or acid partners in these equilibria. R-COO - and R-NH2 are conjugated bases (i.e. proton acceptors) of the corresponding acids. Normal pH of blood is 7.4 at this pH carboxyl groups exist almost entirely as the conjugated base i.e. R-COO-.

73. D. Amino Acid: Structure of Amino Acids: Based on the structure of amino acids in proteins, they are classified into seven classes as follows: Their examples are also cited along with type of class. With aliphatic side chains: Glycine, alanine , valine , leucine and isoleucine . With side chains containing hydroxyl (-OH) groups: Serine, threonine . With side chains containing sulphur atoms: Cysteine, methionine . With side chains containing acidic groups: Aspartic acid, glutamic acid. With side chains containing basic groups: Arginine , lysine, hydroxyl lysine, histidine . With side chains containing aromatic rings: Phenyl alanine , tyrosine, tryptophan. Imino acids: Proline , hydroxyproline .

74. D. Amino Acid: Some of the physiologically active and naturally occuring peptides are as follows:

75. D. Amino Acid: Glutathione: It is a tripeptide consisting of glutamic acid, cysteine and glycine . It is converted to disulphide form by dehydrogenation and is involved in oxidation-reduction reaction. It is required for action of several enzymes and that of insulin. Oxytocin and vasopressin: These are cyclic peptide hormones consisting of 8 amino acids and located in pituitary gland. Oxytocin functions on uterine muscle and aids in ejection of milk.

76. D. Amino Acid: Carnocin : It is a dipeptide consisting of β - alanine and histidine . It is a dipeptide of voluntary muscle. Bradykinin : It is a monopeptide consisting of 9 amino acids. It is most potent pain- producing substance. It mediates production of PGE2 from arterial walls.

77. D. Amino Acid: Angiotensin: Agniotensin I consists of 10 amino acids and has slight effect on blood pressure. Angitoensin I is further converted to Angiotensin II by splitting two amino acid. Angiotensin II has prominent effect on blood pressure. It stimulate thirst, causes dilation of blood vessels of voluntary muscles and brain. Antibiotics: Biologically active antibiotics are obtained from fungi and contain both D- and L- amino acids and amino acids absent in protein.

78. D. Proteins: Proteins are define as high molecular weight mixed polymers of α -amino acids joined together with peptide linkage (-CO-NH-). Proteins are chief constituents of all living matter. They contain carbon, hydrogen, nitrogen, sulphur and phosphorus.

79. D. Proteins: Biological significance of proteins: Protein are essence of life processes. They are fundamental constituents of all protoplasm and are involved in structure and functions of living cells. Enzymes are made up of proteins. The cementing substances and the reticulum which binds or holds the cell as tissues or organs is made up of proteins. Homeostatic control of volume circulating blood and of interstitial fluids is through plasma proteins.

80. D. Proteins: Biological significance of proteins: Proteins are involved in blood clotting through thrombin, fibrinogen and through other protein factors. Antibodies, which are defending factors against infections are proteinous in nature. Nucleoproteins in the cell nucleus perform hereditary transmission.

81. D. Classification of Proteins:

82. 1. Simple Proteins: Sr. No. Class of protein Characteristics Examples 1. Albumins Soluble in water, precipitated at high salt conc. Serum albumin, egg albumin, lactalbumin (milk), etc. 2. Globulins Insoluble in water, soluble in dilute salt solution. Serum albumin, vitelin (egg yolk), turberin (potato), etc. 3. Glutelins Insoluble in water, soluble in dilute acids and alkalies, mostly found in plants. Glutenin (wheat), oryzenin (rice). 4. Prolamines Insoluble in water and absolute alcohol, soluble in 70-80% alcohol. Gliadin (wheat), zein (maize) 5. Protamines Basic proteins of low molecular weight, soluble in water, dil. Acids and alkalies. Salmine (salmon sperm) 6. Histones Soluble in water, insoluble in very dil. Ammonium hydroxide. Globin of haemoglobin and thymus histone . 7. Scleroprtoeins Insoluble in water, dil. Acids and alkalies. Keratin (hair, horn, nail), collagen (bone, skin), etc.

83. 2. Conjugated Proteins: Sr. No. Class of protein Characteristics Examples 1. Nucleoproteins Composed of simple basic proteins ( protamine /histamines) with nucleic acids, located in nuclei, soluble in water. Necleoprotamines , Nucleohistones 2. Lipoproteins Combination of proteins with lipids, e.g. fatty acids, Lipoproteins of egg – yolk, milk, blood, etc. 3. Glycoprtoteins Combination of proteins with carbohydrates. Mucin (saliva), ovomucoid (egg white). 4. Phosphoproteins Contain phosphorous radical as a prosthetic group. Caseinogens (milk), ovovitellin (egg yolk) 5. Metalloproteins Contain metal ions as prosthetic group: Fe, Co, Mg, Zn, etc. Siderophilin (Fe), Ceruloplasmin (Cu) 6. Chromoproteins Contain porphyrin (with iron) as prosthetic group. Heamoglobin , myoglobin, catalase . 7. Flavoproteins Contain riboflavin as their prosthetic group. Flavoproteins of liver and kidney.

84. 3. Derived Proteins: Sr. No. Class of protein Characteristics Examples Primary derivatives 1. Proteans Derived in early stage of protein hydrolysis by dil. Acids, enzymes or alkalies. Fibrin from fibrinogen 2. Metaproteins Derived in later stage of protein hydrolysis by slightly stronger acids and alkalies. Acid and alkali metaproteins 3. Coagulated proteins Denatured proteins formed by the action of heat, X-rays, ultra violet rays. Cooked proteins, coagulated albumins. Secondary derivatives 4. Proteoses Formed by action of pepsin or trypsin . Albumose from albumin, globulose from gloulin 5. Peptones Soluble in water, not precipitated by saturated ammonium sulphate 6. Peptide Containing two or more amino acids. ( di -, tri-, and polypeptides) Glycyl-alanine , leucyl-glutamic acid.

85. Bonds related to Protein Structure: Protein structure are confirmed by two types of bonds: Strong bonds: Peptide bonds: Disulphide bonds: Weak bonds: Hydrogen bonds: Hydrophobic bonds

86. Bonds related to Protein Structure: Strong bonds: Peptide bonds: Proteases produce polypeptide by hydrolyzing proteins. They can also hydrolyze peptide bonds. Polypeptides like proteins react with biuret reagent which is suggestive of two or more peptide bonds.

87. Bonds related to Protein Structure: Strong bonds: Disulphide bonds: The disulphide bond may interconnect two parallel chains through cysteine within each polypeptide. The bond is not broken under usual condition of denaturation. Two peptide chains united by a disulphide linkage

88. Bonds related to Protein Structure: Weak bonds: Hydrogen bonds: The hydrogen bond appears form sharing of hydrogen atoms between the nitrogen and the carbonyl oxygen of different peptide bonds. Each hydrogen bond is relatively weak.

89. Bonds related to Protein Structure: Weak bonds: Hydrophobic bonds: The non-polar side chains of neutral amino acids are closely associated with one another in proteins. There are not true bonds. They play an important role in maintaining structure of proteins.

90. Structure of Proteins: The structure of proteins is considered by several levels of organization as mentioned below: Primary level of organization = Sequence of amino acids. Secondary level of organization = Folding of Polypeptide chains. Tertiary level of organization = Relation between primary and secondary structure. Quaternary level of organization = Aggregation of two and more units.

91. Denaturation of Proteins: It is defined as the disruption of the secondary, tertiary and quaternary structure of the native protein resulting in alteration of the physical, chemical and biological characteristics of protein by a variety of agents. The native proteins are the one which occur in animal and plant tissues in a natural state. Characteristic: solubility, viscosity, optical rotation, sedimentation rate, electrophoretic mobility, etc. during denaturation.

92. Biological Significance of Denaturation: Precipitation of native protein as a result of denaturation is used to advantage in the clinical laboratory. Blood or serum samples to be analyzed for small molecules. It is used to know the enzyme-catalysed reaction of an extract at the loss of enzyme activity when boiled and acidified. A denatured protein can be renatured by appropriate changes in the salt concentration used to precipitate the protein.