Ch-09,Biomolecules Class XI - PowerPoint Presentation

1. Ch-09,BiomoleculesClass XI sir

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5. Chemicals or molecules present in the living organisms are known as BiomoleculesThe sum total of different types of biomolecules, compounds and ions present in a cell is called as cellular poolBiomolecules are compounds of carbon. Hence the chemistry of living organisms is organized around carbon.Carbon is the most versatile and the most predominant element of life.ELEMENTNon living (Earth crust)Living MatterHydrogen0.140.5Carbon0.0318.5Oxygen46.665.0Nitrogen Very less3.3Sulphur0.030.3Sodium2.80.2Calcium3.61.5Magnesium2.10.1Silicon27.7Very less

6. Biomolecules Any living tissue (a vegetable or a piece of liver, etc.) and grind it in trichloroacetic acid (Cl3CCOOH) using a mortar and a pestle. We obtain a thick slurry. Strain slurry through a cheesecloth or cotton. Obtain two fractions. One is called the filtrate or more technically, the acid-soluble pool, and The second, the retentate or the acid-insoluble fraction.Scientists have found thousands of organic compounds in the acid-soluble

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8. contAll the carbon compounds that we get from living tissues can be called ‘bio-molecules’. However, living organisms have also got inorganic elements and compounds in them.

9. contThe tissue is fully burnt and converted into ‘ash’. This ash contains inorganic elements (like calcium, magnesium etc). Inorganic compounds like sulphate, phosphate, etc., are also seen in the acid-soluble fraction. Therefore elemental analysis gives elemental composition of living tissues in the form of hydrogen, oxygen, chlorine, carbon etc. while analysis for compounds gives an idea of the kind of organic (Figure 9.1) and inorganic constituents (Table 9.2)

10. Biomolecules From a chemistry point of view, it can identify by functional groups like aldehydes, ketones, aromatic compounds, etc. But from a biological point of view, we shall classify them into amino acids, nucleotide bases, fatty acids etc.

11. sirBIOMOLECULESInorganicOrganicMineralsGasesWaterCarbohydratesLipidsAmino acidsProteinsEnzymesNucleotidesNucleic acidsVitamins

12. sirBIOMOLECULESMicromoleculesMineralsGasesWaterSugarsAmino acidsnucleotidesCarbohydratesLipidsProteinsNucleic acidsMacromoleculesSmall sized, low mol wtBetween 18 and 800 daltonsFound in the acid soluble poolLarge sized, high mol wtAbove 10000 daltonsFound in the acid insoluble pool

13. sirBiomoleculeBuilding blockMajor functionsProteinAmino acidBasic structure and function of cellDNADeoxyribonucleotideHereditary informationRNARibonucleotideProtein synthesisPolysaccharide MonosaccharideStorage form of energyLipidsFatty acids & glycerolStorage form of energy to meet long term demandsThe major complex biomolecules of cells

14. sirProteins

15. sirPROTEINSMost abundant organic molecules of the living system.They form about 50% of the dry weight of the cell.They are most important for the architecture and functioning of the cell.Proteins are polymers of amino acids Proteins on complete hydrolysis yields Amino AcidsThere are 20 standard amino acids which are repeatedly found in the structure of proteins – animal, plant or microbial.Collagen is the most abundant animal protein and Rubisco is the most abundant plant protein .Protein Synthesis is controlled by DNA.

16. Amino acidsAmino acids are organic compounds containing an amino group and an acidic group as substituents on the same carbon i.e., the α-carbon.Hence, they are called α-amino acids. They are substituted methanes. There are four substituent groups occupying the four valency positions. These are hydrogen, carboxyl group, amino group and a variable group designated as R group. Based on the nature of R group there are many amino acids.

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20. sirAMINO ACIDSAmino acids are group of organic compounds having 2 functional groups (-NH2) and (-COOH)(-NH2) group is basic whereas (-COOH) is acidicR- can be H in glycine, CH3 in alanine, Hydroxymethyl in serine in others it can be hydrocarbon chain or a cyclic groupAll amino acids contain C, H, O and N but some of them additionally contain SPhysical and chemical properties of amino acids are due to amino, carboxyl and R functional groups Amino acids are differentiated into 7 groups

21. sirNo.NatureAmino acids1.NEUTRAL : Amino acids with 1 amino and 1 carboxyl groupGlycine (Gly), Alanine (Ala), Valine (Val), Leucine (Leu), Isoleucine (Ile)2.ACIDIC : 1 extra carboxyl groupAspartic acid (Asp), Asparagine (Asn), Glutamic acid (Glu), Glutamine (Gln)3.BASIC : 1 extra amino groupArginine (Arg), Lysine (Lys) 4.S – CONTAINING : Amino acids have sulphurCysteine (Cys), Methionine (Met)5.ALCOHOLIC : Amino acids having –OH groupSerine (Ser), Threonine (Thr), Tyrosine (Tyr)6.AROMATIC : Amino acids having cyclic structurePhenylalanine (Phe), Tryptophan (try)7.HETEROCYCLIC : amino acids having N in ring structureHistidine (His), Proline (Pro)

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23. ESSENTIAL AMINO ACIDST2 L2 I M V P (Can not synthesised by our body) TryptophanThreonineLysineLeucineIsoleucineMethionineValinePhenylalanineSemi-Arginine and Histidine23

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26. Zwitterions Zwitterions (the word is derived from the German for "hybrid ion") are ions that are electrically neutral overall but contain nonadjacent regions of positive and negative charges; they are sometimes referred to as "dipolar ions." The best-known examples of zwitterions are the free amino acids found in cells.An examination of the general structure of an amino acid reveals that there are two parts, or groups, of the molecule that can function as an acid/base pair, the –COOH and –NH2 groups. At pH values near neutrality, a protein transfer reaction takes place that results in the –COOH becoming –COO− and the –NH2 becoming –NH3+. A large favorable (stabilizing) electrostatic interaction now develops between these two parts of the molecule. This interaction is favorable enough to shift the equilibrium constant for the proton transfer reaction toward the formation of the charged species, by a factor of between 10– and 50–fold.

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28. sirAspartic acid (acidic)Alanine (neutral)Lysine (basic)Serine (alcoholic)Cysteine (suphur)Phenylalanine (aromatic)

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30. sirPEPTIDE FORMATIONAmino acids are linked serially by peptide bonds (-CONH-) formed between the (-NH2) of one amino acid and the (-COOH) of adjacent amino acid.Chain having 2 amino acids linked by a peptide bond is called as a DIPEPTIDEThe sequence of amino acids present in a polypeptide is specific for a particular protein.

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36. Ramachandran plot  Ramachandran plot (also known as a Rama plot, a Ramachandran diagram or a [φ,ψ] plot), originally developed in 1963 by G. N. Ramachandran, C. Ramakrishnan, and V. Sasisekharan, is a way to visualize energetically allowed regions for backbone dihedral angles ψ against φ of amino acid residues in protein structure.Each peptide bond holds six atoms in a plane. The alpha carbon (C-α) in the center of each amino acid is held in the main chain by two rotatable bonds. The dihedral (torsion) angles of these bonds are called Phi and Psi (in Greek letters, φ and ψ).

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40. sirSTRUCTURE OF PROTEIN4 basic structural levels are assigned to proteins – primary, secondary, tertiary and quaternary.PRIMARYThe primary structure refers to the number and linear sequence of amino acids in thepolypeptide chain and the location of thedisulphide bridges.The primary structure is responsible for the function of the protein.The N-terminal amino acid is written on the left side whereas the C- terminal amino acid is written on the right side

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46. sirSECONDARYThe folding of the linear chain into a specific coiled structure is called as secondary structure.3 types : α- helix, β- pleated sheet and collagen helixα- helixβ- pleated sheetCollagen helix

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49. TERTIARYThe helical polypeptide may fold upon itself and assume a complex but specific form – spherical, rod like or something in between.These geometrical shapes are known as tertiary (30) structure QUATERNARYProteins are said to be quaternary in structureIf they have 2 or more polypeptide chainsHaemoglobin is an excellent example

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54. sirPROTEINSFunctionChemical nature and solubilityNutritional importance

55. sirFunctional classificationStructural proteins e.g. keratin, collagenEnzymatic proteins e.g. pepsinTransport proteins e.g. HaemoglobinHormonal proteins e.g. Insulin, Growth hormoneContractile proteins e.g. Actin, myosinStorage proteins e.g. OvalbuminGenetic proteins e.g. NucleoproteinsDefence proteins e.g. ImunoglobulinsReceptor proteins e.g. for hormones and viruses

56. sirClassification based on chemical nature and solubilitySimple proteins : They are composed only of amino acid residues2. Conjugated proteins : Along with amino acids , there is a non-protein prosthetic group.3. Derived proteins : They are denatured or degraded products of the above two.

57. ProteinsSimpleConjugatedDerivedNucleoproteinsGlycoproteinsMucoproteinsLipoproteinsPhosphoproteinsChromoproteinsMetalloproteinsGlobularFibrousGlobulinHistonesAlbuminElastinKeratinCollagenPrimarySecondaryProteansMetaproteinsCoagulatedproteinsprotonesPeptidesProteoses

58. sirCARBOHYDRATESCarbohydrates are the most abundant organic molecules in nature.The term carbohydrate is derived from the French term hydrate de carbone i.e. it is a hydrate of carbon or Cn(H2O)nCarbohydrates are defined as organic substances having C, H & O Wherein H and O are in the ratio 2:1 as found in H2OFUNCTIONS OF CARBOHYDRATESMost abundant source of energy (4 kcal/g =17kJ/g)Precursors for many organic compounds (fats, amino acids)Present as glycoproteins and glycolipids in the cell memebrane and functions such as cell growth and fertilizationPresent as structural components like cellulose in plants, exoskeleton of some insects, cell wall of microorganismsStorage form of energy (glycogen) to meet the energy demands of the body.

59. sirCARBOHYDRATESMONOSACCHARIDESOLIGOSACCHARIDESPOLYSACCHARIDESBasic units of carbohydratesCannot be hydrolysed into smaller unitsThey can be further hydrolysedNon crystalline, non soluble in water, tasteless, on hydrolysis gives mol of monosaccharidese.g. starch , celluloseBased on the no. of C-atomsBased on the type of functional groupDisaccharidesTrisachharidesTetrasachharides

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61. sirMONOSACCHARIDESBased on the no of C-atomsBased on the functional group- Trioses (C3H6O3) e.g. Glyceraldehyde, Dihydroxyacetone- Tetroses (C4H8O4) e.g. Erythrose, Threose- Pentoses (C5H10O5) e.g. Ribulose, Xylose Arabinose(deoxyribose – C5H10O4)- Hexoses (C6H12O6) e.g. glucose, fructose galactose, mannose- Heptoses (C7H14O7) e.g. sedoheptulose glucoheptoseAldoses : the functional group is Aldehyde –CHOe.g. Glyceraldehyde, glucoseKetoses : the functional group is ketone ( C = O)e.g. Dihydroxyacetone, fructose

62. Aldose and ketose

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65. glucose

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67. GLYCOSIDIC BOND

68. sucrose

69. Glycosidic bond

70. sirDerivatives of MonosaccharidesDeoxy Sugars : Deoxygenation of ribose produces deoxyribose, which is a structural component of DNA2. Amino Sugars : When 1 or more –OH groups of monosaccharides are replaced by –NH2 (amino group) it forms an amino sugar e.g. Glucosamine, which forms chitin, fungal cellulose, hyaluronic acid. 3. Sugar Acid : Oxidation of –CHO or –OH group forms sugar acids. Ascorbic acid is a sugar acid4. Sugar alcohols : Reduction of aldoses or ketoses. Glycerol and Mannitol.

71. sirOLIGOSACCHARIDESThey are formed by condensation of 2-9 monosaccharidesDepending upon the no. of monosachharide molecules they are : Disaccharides (sucrose, lactose)Trisaccharides (raffinose=glucose+galactose+fructose)Tetrasaccharides (stachyose=glucose+2 galactose+fructose)The smallest and the commonest oligosaccharides are Disaccharides

72. sirDISACCHARIDESA disaccharide consists of 2 monosaccharide units (similar or dissimilar) held together by a glycosidic bond.They are crysatalline, water soluble and sweet to taste.MALTOSE : - is also called as malt sugar. - made up of 2 glucose moleculesLACTOSE : - is also called as milk sugar as it is found naturally in milk - made up of glucose and galactose - souring of milk is due to conversion of lactose to lactic acid SUCROSE : -is also called as cane sugar. It is the sugar found in sugar cane and sugar beet - most abundant among naturally occurring sugars. - Important source of Dietary carbohydrates - made up of glucose and fructose

73. POLYSACCHARIDESAlso called as GLYCANSMade up of repeating units of monsaccharides held by glycosidic bondsDuring its formation a water molecule is released at each condensation.This helps reduce the bulk making it almost insoluble decreasing its effect on the water potential or osmotic potential of the cell. - Unlike sugars they are not sweet.They are ideal as STORAGE AND AS STRUCTURAL COMPONENTSThey are of 2 types Homoglycans and Heteroglycans. HOMOGLYCANS-Made up of only 1 type of monosaccharide monomers-For eg starch, glycogen, cellulose -Glucan (made up of glucose)-Fructan(made up of fructose) -Galactan (made up of galactose)HETEROGLYCANS-Made up condensation of2 or more types of monosaccharidesFor eg Hyaluronic acid, agar, Chitin, peptidoglycans etc

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75. sirSTORAGEPOLYSACCHARIDESSTARCHCarbohydrate reserve of plants and the most important dietary source for animalsHigh content of starch in cereals, roots, tubers, vegetables etc.Homopolymer made up of GLUCOSE units. Also called as GLUCAN.Starch = Amylose + Amylopectin (polysaccharide components)GLYCOGENCarbohydrate reserve in animals. Hence referred as animal starchHigh concentration in Liver, muscles and brain.Also found in plants that do not have chlorophyll (yeast and fungi)GLUCOSE is the repeating unit.INULINPolymer of fructose i.e. fructosanFound in Dahlia, bulbs, garlic, onion etcEasily soluble in waterInulin is not readily metabolised in the human body and is readily filtered through the kidney. Hence used for testing kidney function (GFR).

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78. cellulose

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81. sirSTRUCTURALPOLYSACCHARIDESCHITINSecond most abundant organic substance.Complex carbohydrate of Heteropolysaccharide type.Found in the exoskeletons of some invertebrates like insects and crustaceans. Provides both strength and elasticity.Becomes hard when impregnated with calcium carbonate.CELLULOSEOccurs exclusively in plants and is the most abundant organic substance in plant kingdom.Predominant constituent of plant cell wall.It is totally absent in animals.

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83. Lipids Biomolecules

84. sirWith the water, I say, Touch me not,To the tongue, I am tasteful,Within limits, I am dutiful,In excess, I am dangerousLIPIDS

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87. lipidsLipids are generally water insoluble. They could be simple fatty acids.A fatty acid has a carboxyl group attached to an R group. The R group could be a methyl (–CH3), or ethyl (–C2H5) or higher number of –CH2 groups (1 carbon to 19 carbons).For example, palmitic acid has 16 carbons including carboxyl carbon. Arachidonic acid has 20 carbon atoms including the carboxyl carbon.

88. lipidFatty acids could be saturated (without double bond) or unsaturated (with one or more C=C double bonds). Another simple lipid is glycerol which is trihydroxy propane. Many lipids have both glycerol and fatty acids. Here the fatty acids are found esterified with glycerol. They can be then monoglycerides, diglycerides and triglycerides. These are also called fats and oils based on melting point. Oils have lower melting point (e.g., gingely oil) and hence remain as oil in winters.Some lipids have phosphorous and a phosphorylated organic compound in them. These are phospholipids. They are found in cell membrane. Lecithin is one example. Some tissues especially the neural tissues have lipids with more complex structures.

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96. sirLipids are the chief concentrated storage form of energy forming about 3.5% of the cell content.Lipids are organic substances relatively insoluble in water but soluble in organic solvents (alcohol, ether)Functions : They are the concentrated fuel reserve of the body.Lipids are constituents of membrane structure and regulate the membrane permeability.3. They serve as source of fat soluble vitamins4. Lipids are important cellular metabolic regulators5. Lipds protect the internal organs and serve as insulating materials

97. phospholipids

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101. sirLIPIDSSimpleComplexDerivedPhospholipidsGlycolipidsLipoproteinsFats & OilsWaxesSteroidsTerpenes

102. sirSIMPLE LIPIDSThey are esters of fatty acids with alcohol. They are of 2 types : 1. Neutral or true fats : Esters of fatty acids with glycerol 2. Waxes : Esters of fatty acids with alcohol other than glycerol.Neutral / True fatsTrue fats are made up of C, H, & O but O is lessA fat molecule is made up of 2 components : GLYCEROL b) FATTY ACIDS (1-3 mol, of same or diff long chained)

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107. sirGlycerolA glycerol mol has 3 carbons each bearing a –OH groupFatty acidA fatty acid mol is an unbranched chain of C-atoms.It has a –COOH group at one end and a H bonded to almost all the C-atomsFatty acids may be saturated or unsaturated

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112. ESSENTIAL FATTY ACIDSLinolenic AcidLinoleic AcidArachidonic Acid112

113. WAXESLipids which are long chain saturated fatty acids and a long chainSaturated alcohol of high mol wt other than glycerolExample : Bees wax : secretion of abdominal glands of worker honey beesLanolin or wool fat : Secretion of cutaneous glands and obtained from the wool of sheep3. Sebum : secretion of sebaceous glands of skin4. Cerumen : soft and brownish waxy secretion of the glands in the external auditory canal. Also called as Earwax5. Plant wax : Coating formed on the plant organs to prevent transpiration6. Paraffin wax : A translucent waxy substance obtained from petroleum

114. sirCOMPLEX LIPIDSThey are derivatives of simple lipids having additional group like phosphate, N2-base,Protein etc. They are further divided intoPhospholipids, Glycolipids, Lipoproteins.PhospholipidThey are made up of a molecule of glycerol Or other alcohol havingA phos group at 1 of its –OH groups2 fatty acid molecules at other 2 –OH groups3. A nitrogen containing base attatched to phos groupA phospholipid molecule has a hydrophobic tail (fatty acids) and a hydrophilic head(phos group)

115. GlycolipidThey are components of cell membranes, particularly myelin sheath and chloroplast membranesCEREBROSIDE are the most simplest form of glycolipids

116. sirLipoproteinThey contain lipids and proteins in their molecules.They are main constituent of membranes.They are found in milk and Egg yolk.Lipids are transported in blood and lymph as lipoproteins.5 types of lipoproteins : 1. chylomicrons 2. VLDL 3. LDL 4. HDL 5. Free fatty acid albumin complex

117. sirDERIVED LIPIDSThey are derivatives obtained on the hydrolysis of the simple and complex lipids.e.g. steroids, terpenes and prostaglandinsSteroidThe steroids do not contain fatty acids but are included in lipids as they have fat-like properties.They are made up of 4 fused carbon ringsCholesterol, Vit D, testosterone, adrenocortical hormones.The most common steroids are STEROLS.Common sterols are Cholesterol and ergosterol

118. sirTerpenesTerpenes are a major component of essential oils produced by plants. They give fragrance to the plant parts.Vitamins A, E and K contain a terpenoid called phytolCarotenoid pigment is precursor for Vitamin ALycopene, a pigment present in tomatoes is a terpenoidGibberellins, the plant hormone is also a terpene

119. History –nucleic acidNuclein were discovered by Friedrich Miescher in 1869.In 1889 Richard Altmann discovered that nuclein has acidic properties, and it became called nucleic acidIn 1938 Astbury and Bell published the first X-ray diffraction pattern of DNA.In 1953 Watson and Crick determined the structure of DNA.Experimental studies of nucleic acids constitute a major part of modern biological and medical research, and form a foundation for genome and forensic science, and the biotechnology and pharmaceutical industries

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129. sirNUCLEOTIDES

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132. Mechanism of JoiningCarbon Number 1 of Pentose sugar is Joined with the Nitrogen of 9th and 1st Number of Purines and Pyrimidines respectively.Carbon Number 3rd of Pentose sugar is joined with another nucleotide by Phosphate by Phosphoester bond.Carbon Number 5th of Pentose sugar is joined Phosphate by Phosphoester bond.

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134. Phosphodiester bond

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140. SUGARN2 BASESsir

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142. DNAsir

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145. m- RNAr- RNAt- RNAsir

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147. sirENZYMES

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149. ENZYMES149 The name enzyme(en=in,zyme-yeast) literally means in yeast.The term enzyme was coined by Kuhne in 1878.Enzyme was discovered by Buchner.Summer in 1926 isolated first enzyme urease in crystaline form from jack bean and he confirming that enzymes are proteinaceous.All enzymes are protein but all proteins are not enzyme exce.Ribozyme (RNA catalytic) and Abzymes(antibodies activity)

150. Structure of enzymeHoloenzyme(functional)=apoenzyme(proteinous)+cofactor(non-proteinous part).Cofactor are three types1.Coenzyme-loosely attached organic compounds i.e NAD,NADP,FAD,FMN,Vitamins2.Prosthetic group-tightly attached organic compounds3.Activator-metalic element inorganic substance.150

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159. Enzymes are a group of catalysts functioning in a biological systemThey are usually proteinaceous substances produced by the living cell Without themselves getting affected.Enzymes enhance the rate of reaction and are formed in the cell under the instructions of genesENZYMOLOGY is the branch of science that deals with the study of Enzymes in all the aspects like nomenclature, reactions and functionsEnzymes occur in colloidal state and are often produced in inactive form called proenzymes (zymogen), which are converted to their active forms by specific factors like pH, substrate etc.The enzymes that are produced within a cell for metabolic activities are known as endoenzymes and those which act away from the site of synthesis are called exo-enzymes

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161. catalytic cycle of an enzymeThe catalytic cycle of an enzyme action can be described in the following steps:1. First, the substrate binds to the active site of the enzyme, fitting into the active site.2. The binding of the substrate induces the enzyme to alter its shape, fitting more tightly around the substrate.3. The active site of the enzyme, now in close proximity of the substrate breaks the chemical bonds of the substrate and the new enzyme- product complex is formed.4. The enzyme releases the products of the reaction and the free enzyme is ready to bind to another molecule of the substrate and run through the catalytic cycle once again.

162. ENZYME SUBSTRATE COMPLEX

163. EnzymesAre specific for what they will catalyzeAre ReusableEnd in –ase -Sucrase -Lactase -Maltase163

164. Active SiteA restricted region of an enzyme molecule which binds to the substrate.EnzymeSubstrateActive Site

165. Enzyme-Substrate ComplexThe substance (reactant) an enzyme acts on is the substrateEnzymeSubstrateJoins

166. How do enzymes Work?Enzymes work by weakening bonds which lowers activation energy.

167. ACTIVATION ENERGYThe activation energy is the energy required to start a reaction. Enzymes are proteins that bind to a molecule, or substrate, to modify it and lower the energy required to make it react. Enzymes lower the activation energy of a reaction by binding one of the reactants, called a substrate, and holding it in a way that lowers the activation energy. Likewise, an enzyme holds its substrate in such a way that the reaction is much more likely to occur.

168. Activation Energy Enzymes work by lowering the activation energy needed to start a chemical reaction.

169. EnzymesFreeEnergyProgress of the reactionReactantsProductsFree energy of activationWithout EnzymeWith Enzyme

170. MODE OF ACTIONTwo models1.Lock and Key model-Proposed by Fischer2.Indused fit model -Proposed by Khosland(1968) Michaelis –Menton Theory-Lower the value of Mechaleis constant higher the affinity with substrate.

171. Lock and Key Theory:The specific action of an enzyme with a single substrate can be explained using a Lock and Key analogy first postulated in 1894 by Emil Fischer. In this analogy, the lock is the enzyme and the key is the substrate. Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme).Smaller keys, larger keys, or incorrectly positioned teeth on keys (incorrectly shaped or sized substrate molecules) do not fit into the lock (enzyme). 

172. LOCK AND KEY MODEL

173. Induced FitA change in the shape of an enzyme’s active siteInduced by the substrate

174. Group of Enzymes Reactions catalysed Examples1. OxidoreductasesTransfer of O2 or H2 atoms or electrons from one substrate to anotherDehydrogenaseOxidases2.TransferasesTransfer of a specific group from one substrate to anotherTransaminase3.HydrolasesHydrolysis of a substrateDigestive enzymes4. IsomerasesChange of the molecular form of the substratePhospho Hexo isomerase5.LyasesNon hydrolytic removal or addition of a group to a substrateDecarboxylaseAldolase6. LigasesJoining of 2 molecules by formation of new bondsCitric acid synthetase

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176. GENERAL PROPERTIES OF ENZYME AND FACTORS AFFECTING THEIR ACTIVITY Enzymes accelerate the reaction but do not initiate it.2) Enzymes themselves do not participate in the reaction and remain unchanged at the end of the reaction. Enzymes, are therefore, needed in small amounts.The molecule of an enzyme is larger than that of substrate molecule and hence during reaction a specific part of enzyme molecule comes in contact with the substrate molecule. That part is called active site of enzyme.4) Amphoteric nature: Chemically most of the enzymes are proteins and, therefore, show amphoteric nature. The enzymes can react with acidic substances as well as alkaline substances.

177. Specificity: Most of the enzymes are specific in their action. A single enzyme acts upon a single substrate or a group of closely related substrates. For example, the enzyme urease can act only upon urea invertase can act upon sucrose only. A slight change in the configuration of the substrate molecule requires action by a different enzyme.6) Colloidal nature: All enzymes are colloidal in nature and thus provide large surface area for reaction to take place. Colloids (colloids- gel like) are mixtures of two components i.e. dispersed particles and dispersion medium. The size of the dispersed particles is larger than dispersion medium.

178. Enzyme optima : Enzymes generally work best under certain narrowly defined conditions referred to as optima. These include appropriate temperature and PH.Temperature sensitivity : Since the enzymes are proteins, they are affected by change in temperature. With increase in temperature, increase in enzyme activity takes place (up to 40°C). However, when temperature increases above 60°C the proteins undergo denaturation or even complete breakdown. When the temperature is reduced to freezing point or below freezing point the enzymes become inactivated but they are not destroyed. The rate of reaction is more at optimum temperature.b) pH sensitivity : Most of the enzymes are specific to pH and remain active within particular range of pH. The strong acid or strong base denatures enzymes. Most of the intracellular enzymes function best around neutral pH

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180. Concentration of enzyme and substrate : The rate of reaction is proportionate to the concentration of the reacting molecules. If the substrate concentration is increased the rate of enzyme action also increases up to certain limit. Beyond a certain concentration, the enzyme molecules remain saturated with substrate molecules and the activity becomes steady.9) Enzyme inhibitors : Enzyme inhibitors are certain products which inhibit enzyme activity. During the reaction, if the active site of enzyme is occupied by these inhibitors instead of substrate molecules and the activity of enzyme is lost. These substances are like substrate molecules in their structure and are called competitive inhibitors.

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186. What are secondary metabolites ?Secondary metabolites : The materials which do not require for normal growth and development are called secondary metabolites. These are the by-products of plants, eg: Alkaloids, Tannins, Resins, Gums and Latex etc, Though plants produce these chemicals for their own use man found the usage of these chemicals for own benefits. They are generally coloured and fragrant.1) Alkaloids: These are nitrogenous by-products and poisonous. These are stored in different parts of the plants.

187. secondary metabolites2) Tannins: Tannins are carbon compounds. These are stored in different parts of the plant and are deep brown in colour. Tannins are used in tanning of leather and in medicines,e.g.Cassia,Acacia.3) Resin: Occur mostly in Gymnosperms in specialized passages called resin passages. These are used in varnishes, e.g. Pinus.4) Gums: Plants like Neem, Acacia oozes out a sticky substance called gum. When branches are cut. The gum swells by absorbing water and helps in the healing of damaged parts of a plant. Gums are economically valuable and used as adhesives and binding agents in the preparation of the medicines, food, etc.

188. secondary metabolites5) Latex: Latex is a sticky, milky white substance secreted by plants. Latex is stored in latex cells or latex vessels. From the latex of Hevea braziliensis (Rubber plant) rub¬ber is prepared. Latex from Jatropa is the source of bio-diesel.6) Modern chewing gum originally made of chick natural latex from plant.

189. Secondary metabolites7.Abrin is a natural poison that is found in the seeds of a plant called the rosary pea or jequirity pea. These seeds are red with a black spot covering one end. Abrin is similar to ricin, a toxin that also is found in the seeds of a plant (the castor bean plant).8.Ricin, a lectin(a class of proteins, chiefly of plant origin, which bind specifically to certain sugars and so cause agglutination of particular cell types) produced in the seeds of the castor oil plant, Ricinus communis, is a highly potent toxin. A dose of purified ricin powder the size of a few grains of table salt can kill an adult human.

190. Secondary metabolites9. Morphine was first extracted from opium in a pure form in the early nineteenth century. It was used widely as a painkiller during the American Civil War, and many soldiers became addicted. This is narcotic means medically to any psychoactive compound with sleep-inducing properties, and euphoric properties as well.10. Codeine, a less powerful drug that is found in opium but can be synthesized (man-made), was first isolated in 1830 in France by Jean-Pierre Robiquet, to replace raw opium for medical purposes. It is used mainly as a cough remedy.

191. Secondary metabolites11. Concanavalin A (Con A) is a plant lectin that is purified from jack beans. Con A binds to the mannose residues of various glycoproteins and activates lymphocytes. When Con A is administered to mice, liver injury that depends on the activation of T lymphocytes by macrophages occurs 

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193. Peptide bond

194. Glycosidic bond