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= | Viki goes to his scientist friend’s house HO|HAS'MORE DOUBTS? : The scientist who is full of doubts!! | Viki's friend, Dr Panda, was a professor at Department of “Yaar, molecules of this (Yaw, 1 | Chemistry of the University. Viki went on a rickshaw to Dr | liquid are supposed to become | supessedto become rnd ater | | Panda’s house on the University campus. red after reacting with Sulphuric | ee a ela) agit On the way, Viki started a conversation with the rickshaw | Acid but... (bla... bla... rind { | puller, “What is your name?” bla, why it is not happening for last three days. | “Petoo.” ? | have so many doubts arising ; in my mind for last three days.” “OK, Petoo, why did not you study enough?” A worried Dr Panda started “Why should |, Sir?” replied Petoo. “I wanted to pull | Consulting books and sank into eee rickshaw like my father and stay independent.” it. ci ” Viki said.“ ‘ a Viki waited for half an hour and patie 7A Hmm” ,Viki said. “Yes yo ” : te Gi at school you are right in a way!” But had understood that Dr Panda had entirely gee you studied at school you would not have doubts about forgotten about hi se things around you. ‘gotten about his presence. ig Viki did not want to disturb the | The rickshaw puller has no doubts ‘Wat doubt, Sir? person who was so full of questions | ‘What doubt, Sir ?” replied Everything is Clow to and doubts and was trying to salve { How interesting not have the rickshaw puller. “Everything any doubt at al the mysteries surrounding them! So, | feeoneare i is so clear fo me ... | do not Loa he returned without meeting him. friend Dr. Panda: have any doubt at all.” On Viki returns, On the way, he kept on thinking about the two contrasting characters one who had no doubts to worry about and the other wha was full of doubts. By that time, they had reached the residence of Dr. Panda. Viki paid the fare and went in to Dr Panda's house. MORAL OF THE STORY’ Dr Panda is in laboratory 1. Aperson, who knows very little, has no doubts Dr Panda's wife said, “Dr Panda spends his day and | 2. A person, who knows more, has more doubts. night in the Chemistry laboratory. | do not know what is he | IN STUDIES: doing there.”. 1. A student, who studies very less, does not ask Viki ran to the University Chemistry Laboratory and found questions. i a very worried Dr Panda, busy in some tests. Viki said “Yaar, | 2. A person, who studies more, has more doubts to be i what are you doing here?” cleared by teacher. SECTION — A: BSC (DaiLy SCHOLARSHIP CLass) (Theory + Home Assignment Questions) ime TANT NOTE FOR'STUDENTS 1. Home Assignments : You must write (a) the key points of the ans of only those Home Assignments qns, which you are likely to forget, and, (b) the reasoning of the ans of the Home Assignments qns. 2. Key points: Write notes (a) in telegraphic language, (b) in your own handwriting, and (c) in your own language. Key paints will help you to revise the Study Units in minimum time. Always prepare through key points to get the best results. 3. Students must prepare the theory and the home assignments before coming to class. WE WILLLEARN Ti, Introduction. 72. How to Analyse Chemical Composition, T3. Biomacromolecules, T4. Amino Acids & Proteins, TS. Carbohydrates, T6. Nature of bond linking monomers in a polymer, T7. Dynamic state of body constituents - concept of metabolism, T8, Metabolic basis for living, T9. The living state, T10. Enzymes. x 155 INEROD N i sity In living organisms in our sete 0 ranean s plant tissue, ani ee and microbial mass indicates that they are made up similar types of elements and compounds. % Weight of Earth’s crust Element Human Body Hydrogen (H) 0.14 0.5 Carbon (C) 0.03 18.5 ‘Oxygen (0) 46.6 65.0 Nitrogen (N) Very little 3.3 Sulphur (S) 0.03 0.3 Sodium (Na) 2.8 0.2 Calcium (Ca) 3.6 1.5 Magnesium(Mg) 2.1 0.1 Silicon (Si) 27.7 negligible Four elements of carbon, hydrogen, oxygen and nitrogen constitute 97 — 99% of the body of living organisms. Carbon constitutes more than 50% of the dry matter. All compounds or molecules present in the living tissues are called biomolecules. & The essential organic compounds are also called as metabolites. Metabolites are organic compounds that are formed in living beings as a result of their metabolic activity. They are of two types, primary and secondary. Primary metabolites are biochemicals formed as intermediates and products of normal vital metabolic pathways of organisms. They occur in all organisms, e.g., amino acids, nucleotides, sugars, fats, acids, peptides, etc. Animal tissues usually possess only primary metabolites. Plant tissues and microbes also have additional metabolites called secondary metabolites. Secondary metabolites are specialised products formed by alteration of normal or primary metabolic pathways, which have specific functions, e.g. aromatic compounds, alkaloids. A List of Representative Inorganic Constituents of Living Tissues. Component Formula Sodium Na* Potassium K* Calcium Ca** Magnesium Mg** Water H20 Compounds NaCl, CaCOs, POs” S047" o CHs—(CH2)1e—COOH ied gen Fatty acid CH—OH n (Palmitic acid) 1 Reboty 0 CH2—-OH ¢ 9 Glyceral . rf Triglyceride: nl and Ra are ay ay ‘ Reo : CH;—O—P—O—CH25CHe ! ANS, acedety Manet Phospholipid (Lecithin) bite HO Fats and oils (lipids) COOH cgoH Bqor | 4 H—-@—NHa H—G—NHe HOG aNte ‘CH2—OH Glycine Alanine Serine Hi CeH120c (Glucose) CaH100s (Ribose) Sugars (carbohydrates) Amino acids Nucleic Acid : It was first isolated ‘by’ a “Swiss. biochemist Friedrick Miescher from the nuclei of p cells and named this substances as nuclein. Al renamed it latter as nucleic acid due to its acidi properties. The nucleic acids are formed by. polymerisation of a larger no. of repeated units called. as nucleotides. Nucleotides : The nucleotides though considered as. micro molecules are relatively large molecules. Upo acid hydrolysis, they break down. into nucleoside: and phosphoric acids. The nucleosides on furthe hydrolysis with still stronger acid break down int pentose sugars and nitrogen-rich bases. It mean that, they are the condensation products of three, chemicals - a nitrogen base, a pentose sugar. an Phosphoric acid. Being the phosphorylated forms 0 nucleosides, the nucleotides - are © also. calle nucleoside phosphates. £ fone 156 i ENTRATION DURING CLASS, KEEP NOTING PLENTY 0! laotides Nitroge Sugar |Nucleosides puseenue je Pocet jt Baee. IPhosph| jases late fi. DNA nine oxyadenos| d-A [Deoxyadenylic acid ia cue a gs 1 er Deoxyadenosine jonophosphate Pp , Gg Peoxyguanos| dR-G ipeoxyquanylic acid bret ORG fre | lor Deoxyguanosine P jmonophosphate ine} UR-C i idelic acid ICytosine| IDeoxycytidine| yric [Deoxycytidelic st ‘ lor Deoxycytidine | monophosphate P (Thymine} t. ‘a | ORT fthymidine | grr |rhymidelic acid or | [Thymidine Imonophosphate 2. RNA P eee Adenine} R-A adenosine R-A {Adenylic acid or (A) Adenosine | Imonophosphate Pp Guanine} R-G [Guanosine | RG |euanylic acid or (S) | {Guanosine Pp monophosphate Cytosine! Rc loytidine Rc |[Cytidelic acid or (Cc) ICytidine | Imonophosphate Pp af - [ridelic acid or Uracil] RU Uridine RU loridine (U) I monophosphate P l dR = Deoxyribose sugar, R = Ribose sugar, p = Phosphoric acid HOCH; -O. Adenine e HO -P ~ OCHz Adenine OH OH PH Adenosine HOCH,-Ox_Uracil OH OH Adenylic acid OH OH Uridine Nucleosides Nucleotide 2.1 Primary and Secondary Metabolites If one were to make a list of biomolecules, such a list would have thousands of organic compounds including amino acids, sugars, etc.In anima! tissues one notices the presence of all such categories of compounds. These are called primary metabolites. However, when one analyses plant, fungal and microbial cells, one would see thousands of compounds other than © _these called primary metabolites, e.g. “Alkaloides, flavonoides, rubber, essential oils, antibiotics, coloured pigments, scents, gums, spices. These are called secondary metabolites. While primary metabolites have identifiable functions and play knawn roles in normal - physidlogiaf » processes, we do not at the moment, understand the tole or functions of all the ‘secondary metabolites’ in host organisms. However, many of them are useful to ‘human welfare’ (e.g., rubber, drugs, spices, scents and pigments). Some Secondary Metabolites ) Pigments + Carotenoids, Anthocyanins, etc. Alkaloids —» Morphine, Codeine, etc. Terpenoides -» Monoterpenes, Diterpenes etc. Essential oils —» Lemon grass oil, etc Toxins —> Abrin, Ricin , Lectins — Concanavalin A Drugs ~ Vinblastin, curcumin, etc. at. Ans. These are organic compounds that are not directly involved in the normal growth, development or reproduction of organisms. Unlike primary metabolites, absence of secondary metabolities results not in immediate death, but in long-term impairment of the organism's survivabilityfecundity or aesthetics, or perhaps in no. significant change at all. Secondary metabolites are often restricted to a narrow set of species within phylogenetic group. “8 T3. There is one feature common to all those compounds found in the acid soluble pool. They have molecular weights ranging from 18 to around 800 daltons (Da) approximately. The acid insoiuble fraction, has only four types of : organic compounds i.e., proteins, nucleic acids, polysaccharides and lipids. These classes of compounds with the exception of lipids, have molecular weights in the range of ten thousand daltons and above. For this very reason, biomolecules, ie., chemical compounds found in living organisms are of two types. One, those which have molecular weights less than one thousand dalton and are usually referred to as micromolecules or simply biomolecules while those which are found in the acid insoluble fraction are called macromolecules or bio -macromolecules. 158 A e Average Composition of Cells 1. Amino Acids are colourless crystalline, water Component % of the total cellular mass soluble and aminated organic acids formed of C, Water 70490 Eo H, O, Nand in some S. There are some 200 amino acids, out of which 20 occur in proteins. Proteins > 10-15 2. Protein amino acids besides bearing a carboxy! group, possess an amino group attached to a- Carbohydrates’) 1S carbon, hence a-amino acids. The a-carbon also Lipids > 2 bears one hydrogen and hydrocarbon which is i Sekt; case of glycine (simplest and smallest) is a second Nucleic acids => 5-7 hydrogen, NHz.CHR.COOH. ons > 1 3. Proline and hydroxyproline have ~ NH imino group) instead of -NHa2. 4. R-hydrocarbon can be polar (eg., glutamic acid, serine) or nonpolar (e.g., alanine). Lipids are indeed small molecular weight compounds and are present not only as such but also arranged into structures like cell membrane and other ‘ i A membranes. 5. Except for glycine, all ther protein amino acids are . ; . . laevorotatory. When we grind a tissue, we are disrupting the cell 6. Three important nonprotein amino acids are structure. Cell membrane and other membranes are broken into pieces, and form vesicles which are not water soluble. ornithine, citrulline (urea cycle) and diaminopimelic acid. 7. The eight essential aminoacids are leucine, isoleucine, valine, tryptophan, phenylalaline, lysine and methionine and threonine(adults).But arginine and histidine are two semi-essential aminoacids. Therefore, these membrane fragments in the form of vesicles get separated along with the acid insoluble pool and hence in the macromolecular fraction, Lipids are not strictly macromolecules. The acid ® Function: soluble pool represents roughly the cytoplasmic 4. These are the monomeric units (building blocks) of composition. proteins. The macromolecules from cytoplasm and organelles 2, Amino acid derivitatives, amides are used to store become the acid insoluble fraction. nitrogen. 3. Tyrosine is required for the synthesis of many Together they represent the entire chemical hormones such as Thyroxin, tetra iodo thyronin. composition of living tissues or organisms. epinephrine, nor-epinephrine, dopamine etc. — ———— 4. Tryptophan is required for the formation of auxins (indole 3 acetic acid), a plant hormone & vitamin nicotinamide. Q2. (1 Mark) : Name one element invariably found in proteins but not in all carbohydrates and lipids. Ans. Nitrogen 5. Tyrosine is necessary for the formation of skin =
5', % TC Td 165 KZAE. Ea WF WE Ae (f) Reversibility Theoretically, all controlled reactions are reversible, (g) Enzyme Specificity : Enzymes are a highly specific in their. For example, enzyme maltase acts on sugar maltose but not on lactose. (h) Heat sensitivity :All enzymes are heat sensitive or thermolabile. Most enzymes operate optimally between 25° - 35° C. They become inactive at freezing temperatures and denatured at 50° - 55°C, Protein Poisons : Being made of proteins, enzymes are inactivated or denatured by all those substances and forces which destroy protein structure, e.g., heavy metals, high energy radiations. () pH : Each enzyme functions at a particular pH, e.g., pepsin (2 pH). sucrase (4.5pH), salivary amylase (6.8pH). trypsin (8.5pH). . Classification of Enzymes : According to modern system “International union of Biochemists” have recommended a classification in which enzymes are grouped into 6, main divisions which are follows: (a) Oxidoreductases : They include enzymes which bring about the main energy yielding reactions tissue such as oxidation and reduction reactions. Three types of such enzymes can be distinguished namely, oxidases dehydrogenases and redutases. (b) Transferases : These enzymes bring about the transfer to a group of atoms from one molecule to another. Common examples of Transferases are Phosphokinases and Transases (such as transaminases, transketolases, transaldolases, transmethylases etc.) Example is : Glucose+ATP === Glucose -6 PO,+ ADP (c) Hydrolases : This group includes digestive enzymes like carbohydrases, proteases, esterases etc. Examples are : enzyme rt sucrase Sucrose + H20 —“““— > Glucose + Fructose (d) lsomerases : These enzymes bring about conversion of a substrate molecule into different isomeric forms through _ intra- molecular rearrangements, not involving a net change in the concentration of compounds other than the substrate. Example is Phosphogiuco-Isomerase Glucose 6-PO, “===> Fructose- 6-Phosphate (e) Lyases : The enzymes of this group result ina direct breakage of different kinds of bonds like C-C, C-O, C-N etc, Without a hydrolysis or oxidation reduction. Ex. Decarboxy-lase Carboxylases, Aldolases etc. ONCERTRATION DURING CLASS, KEEP NOTING PLENTY OF KEV.POINTS AS TEACHER TEACHES. Fructose 1, 6 diphosphate Site Dihydroxy acetone-+Glyceraldehyde phosphate (f) Ligases ; These are enzymes catalyzing all of the reactions involving the formation of bonds between two substrate molecules that are coupled to the cleavage of a pyrophosphate bond is ATP or another energy donor. AcetylCoA + Oxaloacetic acid —Semess_5 Citric acid, . Structure of Enzymes : Enzymes are made up a proteins. Some enzymes have a non-protein part attached to the protein and are together known as conjugate protein. Such an enzyme is often known as the holoenzyme. The Protein part a of the enzyme is called the apoenzyme and the non- protein part is called the prosthetic group. Usually the prosthetic group is firmly attached to the apoenzyme, but sometimes it is not firmly bound and can also be separated easily. The separable prosthetic group is also known as coenzyme or cofactor. (a) Apoenzyme: - It is the protein part that forms the major component of the enzyme. The sequence of amino acids is specific for specific enzyme. There is a specific area on the apoenzyme which takes part in the reaction called the active site or reaction site or reaction centre. The apoenzyme becomes non functional when the non-protein part is removed from it. (6) Prosthetic group : It is the non-protein part tightly bound to the protein component by chemical bonds and is not removed by dialysis under physiological conditions. But when it is separated it becomes enzymetically inactive. These are of three types : Metalloenzymes : These are simple prosthetic groups composed of a single atom of metal like Fe, Cu, Zn, Mg, Mn; K etc. They are generally with some oxidising enzymes and are also called metal activators. fron porphyrin proteins : These are complex prosthetic groups containing organic compounds of metals like cytochromes. Metaloflavoproteins These are complex prosthetic groups vitamin B complex groups such as thiamine (B1), riboflavin (82), pyridoxine (Be). (c) Co-enzyme and Co-factors : Co-enzymes and Co-factors are distinguished from prosthetic groups by the fact that they are not tightly bound to the protein parts. They are smaller molecules and can be readily separated by dialysis. 167 ING Pl FOISUIEE)TOTRULCNyE THN VTS GMm CONCENTRATION DURING CLASS, KEEP NOT kad WH WAH EAL | LZ Revomncreea Co-enzyme is usually used for organic molecules which actually participate in an enzymetic action, Separation of co-enzyme inactivates the enzyme. é Substrate + NAD‘ —> Product + NADH + H () Co-enzymes like NAD (nicotinamide adenine dinucleotide) or Co-enzyme-!, NADP (nicotinamide adenine dinucleotide phosphate) or co-enzyme-ll, FMN (Flavin monocucleotide, FAD (Flavin adenine dinucleotide) etc. These act as hydrogen carriers and take part in oxidation on reduction reaction. (ii) Co-enzymes like co-enzymes Q(Co-Q)and TPP (thiamine pyrophosphate) take part in oxidative decarboxylation process i.e., removal of Hydrogen and CO2 (iii) Co-enzymes A(Co-A) is involved in transacetylation reaction as acyl group (-SH) carrier. (d) ATP (Adenosine triphosphate) is also a co- enzyme of many reactions which required metabolic energy. Co-factor is a term generally used for inorganic ions linked to the protein part of the enzyme. These are mostly the ians of essential elements like K*, Mg”, Mn**, Ca™*, Fe™*, Zn™*, CI etc. Co. factors are also called activating ions or activators as they activate the enzyme. 5. Mechanism and mode of Enzyme Action : The primary action of the enzyme is to bind the substrate molecules to a specific site on its surface called the active site and to bring these molecules to a state of activation by lowering the amount of energy required to activate them. The process involves two important phenomena : (a) active site and (b) activation energy. (a) Active site : Enzymes are proteins composed of amino acids arranged in polypeptide chains . In few regions on the surface of the enzyme some amino acid groups behaving as functional groups capable of reacting with the substrate molecules and combine with them. These reacting groups carry out catalytic function and are called active site or catalytic site. (b) Activation Energy : At normal temperature the majority of molecules have an average kinetic energy. Some molecules possess higher or lower than the average kinetic energy as they are in a state of collision and accordingly they are called energy rich or energy poor molecules. The minimum excess amount of energy required to activate the substrate molecules to over come the energy barrier is called activation energy. ENERGY, REACTION ————? Fig. 3 ents The enzyme molecules (E) combines with tha substrate molecule (S) to form an enzyme substrate complex (ES). The complex will react to form the product (P) and the enzyme (E) will be released. Since the activation energy needed for the formation and decomposition of the enzyme-substrate _ complex is low almost all the substrate molecules will” participate in the reaction and the rate of reaction i thus accelerated. Mode of Enzyme Action : 1. Lock and key Hypothesis : -It was put forwarde: by Emil Fischer in 1894. According to this - hypothesis, both enzymes and substrate molecules have specific geometrical shapes. In the region of active sites the surface configuratio: of the enzyme is such as to allow the particular. substrate molecules to be held over it. The active sites also contain special groups having - NH2 , COOH - SH for establishing contact with the substrate molecules. The contact is such that the substrate molecules or reactants come together « causing the chemical change. Just as a lock can be opened by its specific key, a molecule can be acted upon by a particular enzyme. This also explains the specificity of enzyme actions. : ©2-@-@3. ENZYME SURSTRATE ENZYME ENZYME, PRODUCTS suastaare ‘COMPLEX + — Env supstaare see MOLECULES moLEcULES «suas tS ‘COMPLEX Fig.4 After coming in contact with the active site of enzyme, the substrate molecules or reactants form a complex called enzyme -substrate complex. in the complexed state the molecules of the substrate undergo chemical change. The product remain attached to the enzyme for some time so that enzyme -product complex is also formed. Howevel the product are soon released and the freed enzymt is able to bind more substrate molecules. 3 Enzyme + substrate = Enzyme - Substrate complex 168 
