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Respiration Q.1. What is respiration? Give the overall equations of aerobic and anaerobic respiration. Ans: 1. Respiration is defined as an intra cellular process of oxidation in which complex organic substances are broken down in stepwise manner with the release of energy which is immediately converted into metabolically usable form of energy (ATP). 2. Equation of aerobic respiration is C6 H12 O6 6O2 6CO2 6H2 O 38ATP 3. Equation of anaerobic respiration is Step Direct ATP Indirect ATP formation formation Via ETS 1. Glycolysi s 2 ATP 2 NADH2 3 = 6 ATP 8 ATP 2. Link reaction -- 2 NADH2 3 = 6 ATP 6 ATP 3. Krebs cycle 2 ATP 6 NADH2 3 = 18 ATP 24 ATP C6 H12 O6 6CO2 6H2 O 38ATP Total ATP 2 FADH2 2 = 4 ATP Q.2. Draw a neat and labelled diagram showing ultrastructure of mitochondrion. Total ATP 4 ATP + 34 ATP =38 ATP Q.4. Describe the connecting between glycolysis and Kerbs cycle. Link reaction Ans: 1. Link reaction is acet;ylation of pyruvate. yruvate is formed by glycolysis and it underdergoes oxidative decarboxylation before entering Kerbs cycle. 2. Link reaction mitochondrion. Fig: Ultrastructure of mitochondrion Q.3. Give the balanced sheet of ATP formed in aerobic respiration. Ans: takes place 3. Here removal of CO2 along with from Pyruvate occurs. 4. It is catalysed by pyruvic 5. Coenzymes like NAD and CoA are in matrix hydrogen dehydrogenase. required. 6. End product acetyl CoA enters Kerbs cycle 7. NADH2 formed enters ETS. of 8. Thus from one glucose there forms 2 pyruvate and 2 NADH2 3 = 6 ATP 9. Link Reaction is. 2 pyruvate + 2 NAD + 2CoA 2 Acetyl CoA + 2 NADH2 + 2 CO2 Q.5. Give the significance of respiration. Ans: (i) Respiration provides energy for biosynthesis of cellular materials such as carbohydrates, proteins, fats, lipids, vitamins, pigments, etc. (ii) It is also a source of energy for cell division, growth, repairs and replacement of worn out parts, movements, locomotion etc. (iii) Various intermediates of Kerbs cycle are used as building blocks for synthesis of other complex compounds. (iv) Coupled with photosynthesis, it helps to maintain the balance between CO2 and O2 in the atmosphere. (v) Anaerobic respiration (fermentation) is used in various industries such as dairies, bakeries, distilleries, leather industries, paper industries, alcohol, organic acids, vitamins, antibiotics etc. (vi) Energy of respiration is also used to convert insoluble substances into soluble form. 6. How much energy is released when one molecule of ATP is hydrolysed to ADP and iP? Ans: When ATP is hydrolysed to ADP and iP, then 7.3 Kcal of energy gets released. Q.7. Ans: 1. Chemically ATP is Adenosine triphosphate, thus it is triphosphate ester of adenosing ribonucleoside. 2. It has 3 components- Adenine, ribose (C5H10O5) and 3 phosphate groups. Q.8. ATP is called energy currency of cell, Explain. Ans: 1. When energy is released, ATP synthesis takes place from ADP and iP. 2. When energy is required, ATP is hydrolysed and energy is released which is used in metabolic activities. 3. Therefore ATP is called energy cell. currency of Q.9. Differentiate between aerobic and anaerobic respiration. Aerobic respiration Anaerobic respiration 1. It requires molecular 1. It occurs in absence oxygen. of oxygen. 2. Here undergoes oxidation. glucose 2. Here glucose complete undergoes incomplete oxidation. 3. Metabolic water is end 3. Water is not the end product product 4. More energy (38 ATP) 4. Less energy (2 ATP) is is released released per glucose. 5. Eg. Higher plants and 6. Eg. Few bacteria, animals yeast Describe structure of ATP. Q.10. What is respiratory Quotient? Ans: 1. The ration of volume of CO2 evolved to the volume of O2 consumed in respiration is called respiratory ration (RQ). 2. It depends on the type of respiratory substrate when carbohydrates are used as respiratory substrate and oxidized completely, i.e. aerobic respiration, the RQ is 1. C6 H12 O6 6CO2 6H2 O Energy 6CO 2 RQ 1 6O 2 3. For proteins and fats RQ is less than 1. 4. In case of anaerobic respiration RQ is infinity as O2 is not used. glycolysis Glucose 2 pyruvic acid+ 2 NADH2 +2ATP reduction 2 Pyruvic acid +2NADH2 2Lactic acid +2NAD Q.13. Explain respiration is an Amphibolic pathway. Ans: 1. Respiration involves breakdown of substrates (carbohychates, fats, proteins) and hence it is catabolic process. But some intermediates of respiration are used in biosynthesis (Anabolism) of molecules, thus respiration is called Amphibolic i.e. both catabolic and anabolic pathway. 2. Respiratory intermediates can biosynthesis of fatly acids and glycerol. Q.11. What is fermentation. fermentation? Give uses of Ans: 1. Fermentation is a chemical change brought about in an organic substrate due to enzyme activity of microorganisms. beused for 3. Many acids of Kerbs cycle are used for synthesis of aminoacids and thus proteins. 4. Thus respiratory intermediates Link during synthesis as well as breakdown processes. 2. There are many applications of fermentation in industries and household products. 3. Examples- Curd is produced by lactic acid fermentation yeast is used in Bakery and Brewery for alcohol fermentation. Production of various antibiotics and vitamins is also based on fermentation. Long Answer Questions Q.1. Describe various steps involved in glycolysis. Ans: 1. Glycolysis is the first step involved in both aerobic and anaerobic respiration. 2. It takes place in cytoplasm. Q.12. Explain lactic acid fermentation. Ans: 1. Production of curd from milk is lactic acid fermentation. It is carried out by Lactic acid bacteria. 2. First milk sugar Lactose is converted into glucose. 3. In second stem Glucose undergoes glycolysis to form pyruvate. Then pyruvate undergoes reduction ot form Lactic acid. 4. Lactose Glucose + galactos 3. It is independent of oxygen. 4. It is ten steps process which is controlled by different enzymes. 5. Glycolysis or EMP pathway consists of two major phasesA) Preparatory phase and cleavage (steps 1-5) In preparatory phase glucose is activated by phosphorylation and converted into fructose 1,6 diphosphate. In cleavage it is converted or splitted into two triose phosphates 3- Phosphogly ceraldehyde (PGAL) and dihydroxy acetone phosphate (DHAP). As they are isomers, there forms 2 molecules of PGAL. In this phase 2 ATP are used. B) Oxidative and payoff phase (steps 6-10) In this phase oxidation occurs by removal of hydrogen to form 2 NADH2 molecules. In 2 different steps 4 ATP are formed. 6. Various steps involved in glycolysis can be schematically represented as follows. Some short forms used are PGA = phosphoglyceric acid PEPA= phosphoenol pyruvic acid. 7. Significance of glycolysis :1. At the end of glycolysis, one glucose molecule is converted into two molecules of pyruvate (3c). 2. In preparatory phase 2 ATP are used and in payoff phase & ATP are generated. Thus there is a net gain of 2ATP. 3. The 2 NADH2 formed during oxidative step (6), pass via ETS to produce (2 3ATP 6ATP) total 6 ATP. 4. Thus in aerobic respiration, total gain of 8 ATP via glycolysis is 2ATP+ 6ATP = 8ATP 5. Glycolysis reactions can be presented as 2 Glucose + 2ADP + 2 iP+ 2 NAD 2Pyruvate + 2 ATP +2 NADH2. Q.2. What is TCA/Kerbs cycle ? Describe its different steps. Ans: 1. Second phase in aerobic respiration 0in Kerbs cycle as various steps are described by Hons Kerbs. Its first stable product formed is citric acid (6c), hence it is called citric Acid cycle. In this cycle first & acids (citrate, cis -aconitate, isocitrate, oxalosuccinate). contain three carboxylic acid groups, hence it is called Tricarboxylic Acid cycle- TCA cycle. 9. Oxidation –IV _ Malate dehydrog enase 2. This cycle occurs in mitochondrial matrix only if oxygen is available in the cell. 2) During each turn 3 molecules of water are used up and 2 molecules of CO2 are released. 3. There are many steps each is catalysed by specific enzyme. 3) Two turns of cycle produces 6 NADH2, 2 FADH2 and 2 ATP. 4. Acetyl CoA enters the cycle and undergoes complete oxidation and forms reduced conenzymes NADH2 and FADH2. 4) Total gain of ATP via Kerbs cycle as follows . 5. There are 4 oxidation (dehydrogenation) steps and 2 decarboxylation steps. 6. Initial acceptor (oxaloacetic acid) of acetyl CoA is regenerated. 7. Major reactions of Kerbs cycle - Enzymes involved 1. Condensation - Citrate synthetase 2. Isomerisation – Aconitase (Dehydration, Hydration) 3. Oxidation (Dehydrogenation)-I dehydrogenase 4. Decarboxylation dehydrogenase – I 5. Oxidative decarboxylation – II -dehydrogenase -- – Isocitrate Oxalosuccinate - ketoglutarate 6. Hydration and phosphorylation – Succinate Thiokinase 7.Oxidation – III --- succinate dehydrogenase (dehydrogenation – III) 8. Hydration --- Fumarase (dehydrogenation-IV) 9. Significance of Krebs cycle. 1) Two molecules of pyruvate forms via glycolysis thus Kerbs cycle occurs twice for oxidation of one glucose molecule. Direct ATP formed = 2 ATP Indirect ATP via ETS : = 18 ATP i.e. 6 NADH2 2 ATP = 4 ATP ______ 24 ATP ii) Coenzyme and electron carrier (CoQ or Ubiquinone ) iii) electron carriers = Cytochromes (Fe-proteins) b, c1, c, a, a3 4. Complete oxidation of glucose via glycolysis, Link reaction and TCA cycle produces reduced coenzymes as l0 NADH2 and 2 FADH2. 5. From NADH2 hydrogens are accepted by FMN. Then hydrogen splits into protons and electrons, H2 2H 2e. Protons are released in matrix and electrons pass to CoQ. Electrons then pass through cytochromes b, c, c1, a and a3. Finally electrons are accepted oxygen to form ionic oxygenic which combines with 2H+ from matrix to form metabolic water. This is called terminal oxidation. 6. During electron transport energy is released which is used for biosynthesis of ATP Via oxysomes/F1 particles. This ATP synthesis is called oxidative phosphorylation. Q.3. Illustrate the mechanism of Electron transport system or Terminal oxidation. 7. From one NADH2, 3 ATP molecules form at 3 steps as Ans: 1. The metabolic pathway through which the electrons pass from one carrier to another is called electron transport system (ETS) and it is present on inner mitochondrial membrane. 1. between NADH2 and FMN 2. It involves release of energy from NADH2 and FADH2 and utilize it for the synthesis of ATP. This is accomplished when they are oxidised through ETS and electrons are passed on to O2 resulting in the formation of H2O. 3. Members of ETS are i)hydrogen carriers or coenzymes (NAD, FMN) 2. at cytochrome b and C1 complex 3. at cytochrome a and a3 complex. 8. From one FADH2 2ATP molecules form as electrons from it enters directly at CoQ level and thus first ATP step is omitted. 9. Diagrammatic presentation of ETS. The mechanism of anaerobic respiration involves glycolysis, decarboxylation and reduction. 10. Significance of ETS : 1) It generates major amount of energy in form of ATP. i.e. 34 ATP out of total 38 ATP per glucose. 2) It releases energy in stepwise manner to prevent damage of cells. 3) It regenerates oxidised coenzymes FAD. NAD, 4) It provides water necessary for Krebs cycle. (i) Glycolysis : Glycolysis or EMP Pathway is an anaerobic process and occurs in cytoplasm. It is similar to that of aerobic respiration. During glycolysis, each glucose molecule is broken down into two molecules of pyruvate with the formation of two molecules each of NADH2 and ATP. It may be represented as follows : C6 H12 O6 2NAD 2ADP 2ip 2CH3CO COOH 2NADH2 2ADP 2CH3 CO COOH pyruvate Decarboxylase 2CH3 CHO 2CO 2 TPP Zn Q.4. Describe the mechanism of anaerobic respiration. Ans: Anareobic Respiration : Incomplete oxidation of the respiratory substrate in the absence of oxygen to yield CO2 and ethyl alcohol is called anaerobic respiration. It give relatively less amount of energy. A number of bacteria and some fungi such as yeasts show anaerobic respiration. It occurs in cytoplasm onkly and gives net gain of 2 ATP per glucose molecule. (ii) Decarboxylation: Pyruvate undergoes decarboxylation by removal of a CO2 molecule. It occurs in presence of the enzyme pyruvate decarboxylase to give acetaldehyde. Coenzyme thiamine pyrophosphate (TPP) and the cofactor Zn++ is necessary for this reaction. (ii) Reduction: Acetaldehyde is reduced to ethyl alcohol by the reduced coenzyme NADH2. The reaction occurs in presence of the enzyme dehydrogenase. NADH2 is oxidized to NAD. Dehydrogenase 2CH3 CHO 2 NADH2 2CH3CHOH COOH 2NAD