1. Incomplete oxidation of glucose into pyruvic acid with several intermediate steps is known as
(a) TCA-pathway
(b) glycolysis
(c) HMS-pathway
(d) Krebs cycle
2. NADP+ is reduced to NADPH in
(a) HMP
(b) Calvin Cycle
(c) glycolysis
(d) EMP
3. R.Q. is
(a) C/N
(b) N/C
(c) CO2/O2
(d) O2/CO2
4. End product of glycolysis is
(a) acetyl CoA
(b) pyruvic Acid
(c) glucose 1-phosphate
(d) fructose 1-phosphate
5. R.Q. is ratio of
(a) CO2 produced to substrate consumed
(b) CO2 produced to O2 consumed
(c) oxygen consumed to water produced
(d) oxygen consumed to CO2 produced
6. EMP can produce a total of
(a) 6 ATP
(b) 8 ATP
(c) 24 ATP
(d) 38 ATP
7. Connecting link between glycolysis and Krebs cycle is/before entering Krebs cycle pyruvate is changed to
(a) oxaloacetate
(b) PEP
(c) pyruvate
(d) acetyl CoA
8. Out of 36 ATP molecules produced per glucose molecule during respiration
(a) 2 are produced outside glycolysis and 34 during respiratory chain
(b) 2 are produced outside mitochondria and 34 inside mitochondria
(c) 2 during glycolysis and 34 during Krebs cycle
(d) All are formed inside mitochondria
9. End products of aerobic respiration are
(a) sugar and oxygen
(b) water and energy
(c) carbon dioxide, water and energy
(d) carbon dioxide and energy
10. At a temperature above 35ºC
(a) rate of photosynthesis will decline earlier than that of respiration
(b) rate of respiration will decline earlier than that of photosynthesis
(c) there is no fixed pattern
(d) both decline simultaneously
11. Oxidative phosphorylation is production of
(a) ATP in photosynthesis
(b) NADPH in photosynthesis
(c) ATP in respiration
(d) NADH in respiration
12. When one glucose molecule is completely oxidised , it changes
(a) 36 ADP molecules into 36 ATP molecules
(b) 38 ADP molecules into 38 ATP molecules
(c) 30 ADP molecules into 30 ATP molecules
(d) 32 ADP molecules into 32 ATP molecules
13. Apparatus to measure rate of respiration and R.Q. is
(a) Auxanometer
(b) Potometer
(c) Respirometer
(d) Manometer
14. Terminal cytochrome of respiratory chain which donates electrons to oxygen is
(a) Cyt. b
(b) Cyt. c
(c) Cyt. a1
(d) Cyt. a3
15. End product of citric acid/Krebs cycle is
(a) citric acid
(b) lactic acid
(c) pyruvic acid
(d) CO2 + H2O
16. Out of 38 ATP molecules produced per glucose, 32 ATP molecules are formed from NADH/FADH2 in
(a) respiratory chain
(b) Krebs cycle
(c) oxidative decarboxylation
(d) EMP
17. Life without air would be
(a) reductional
(b) free from oxidative damage
(c) impossible
(d) anaerobic
18. Maximum amount of energy/ATP is liberated on oxidation of
(a) fats
(b) proteins
(c) starch
(d) vitamins
19. ATP is injected in cyanide poisoning because it is
(a) necessary for cellular functions
(b) necessary for Na+ – K+ pump
(c) Na+ – K+ pump operates at the cell membranes
(d) ATP breaks down cyanide
20. Fermentation products of Yeast are
(a) H2O + CO2
(b) methyl alcohol + CO2
(c) methyl alcohol + Water
(d) ethyl alcohol + CO2
21. Respiratory substrate yielding maximum number of ATP molecule is
(a) ketogenic amino acids
(b) glucose
(c) amylose
(d) glycogen
22. In animal cells, the first stage of glucose breakdown is
(a) Krebs cycle
(b) glycolysis
(c) oxidative phosphorylation
(d) E.T.C.
23. Which of the following is essential for conversion of pyruvic acid into acetyl Co-A?
(a) LAA
(b) NAD
(c) TPP
(d) All of these
24. Respiratory quotient (R.Q.) for fatty acid is
(a) > 1
(b) < 1
(c) 1
(d) 0
25. Oxidative phosphorylation involves simultaneous oxidation and phosphorylation to finally form
(a) pyruvate
(b) NADP
(c) DPN
(d) ATP
26. The enzymes hexokinase which catalyses glucose to glucose-6-phosphate in glycolysis is inhibited by glucose-6- phosphate. This is an example of
(a) competitive inhibition
(b) non-competitive inhibition
(c) feedback allosteric inhibition
(d) positive feedback.
27. Krebs cycle occurs in
(a) mitochondria
(b) cytoplasm
(c) chloroplasts
(d) ribosomes
28.Fermentation is anerobic production of
(a) protein and acetic acid
(b) alcohol, lactic acid or similar compounds
(c) ethers and acetones
(d) alcohol and lipoproteins
29. The mechanism of ATP formation both in chloroplast and mitochondria is explained by
(a) relay pump theory of Godlewski
(b) Munch‘s pressure/ mass flow model
(c) chemiosmotic theory of Mitchell
(d) Cholondy-Went‘s Model
30. In Krebs cycle FAD participates as electron acceptor during the conversion of
(a) succinyl CoA to Succinic acid
(b) alfa keto glutarate to Succinyl CoA
(c) succinic acid to Fumaric acid
(d) fumaric acid to Malic acid
31. Site of respiration in bacteria is
(a) episome
(b) ribosome
(c) mesosome
(d) microsome
32. Maximum usable energy per mol of glucose metabolised will be generated during
(a) aerobic respiration by germinating seeds
(b) production of methanol by enteric bacteria
(c) fermentation into ethanol by yeast
(d) glycolysis in the skeletal muscle of a sprinter performing a hundred metre dash
33. Net gain of ATP molecules during aerobic respiration is
(a) 36 molecules
(b) 38 molecules
(c) 40 molecules
(d) 48 molecules
34. How many ATP molecules are produced by aerobic oxidation of one molecule of glucose?
(a) 2
(b) 4
(c) 38
(d) 34
35. In alcoholic fermentation
(a) oxygen is the electron acceptor
(b) triose phosphate is the electron donor while acetaldehyde is the electron acceptor
(c) triose phosphate is the electron donor while pyruvic acid is the electron acceptor
(d) there is no electron donor
36. During anaerobic digestion of organic waste, such as in producing biogas, which one of the following is left undegraded?
(a) Cellulose
(b) Lipids
(c) Lignin
(d) Hemi-cellulose
37. During the stage in the complete oxidation of glucose are the greatest number of ATP molecules formed from ADP
(a) glycolysis
(b) krebs cycle
(c) conversion of pyruvic acid to acetyl Co-A
(d) electron transport chain
38. In which one of the following do the two names refer to one and the same thing?
(a) Tricarboxylic acid cycle and urea cycle
(b) Krebs cycle and Calvin cycle
(c) Tricarboxylic acid cycle and citric acid cycle
(d) Citric acid cycle and Calvin cycle
39. In glycolysis, during oxidation electrons are removed by
(a) ATP
(b) glyceraldehyde-3-phosphate
(c) NAD+
(d) molecular oxygen
40. Chemiosmotic theory of ATP synthesis in the chloroplasts and mitochondria is based on:
(a) membrane potential
(b) accumulation of Na ions
(c) accumulation of K ions
(d) proton gradient
41. During the stage in the complete oxidation of glucose are the greatest number of ATP molecules formed from ADP
(a) glycolysis
(b) krebs cycle
(c) conversion of pyruvic acid to acetyl Co-A
(d) electron transport chain
42. How many ATP molecules could maximally be generated from one molecule of glucose, if the complete oxidation of one mole of glucose to CO2 and H2O yields 686 kcal and the useful chemical energy available in the high energy phosphate bond of one mole of ATP is 12 kcal?
(a) Thirty
(b) Fifty -seven
(c) One
(d) Two
43. The bacterium (Clostridium botulinum) that causes botulism is
(a) an obligate anaerobe
(b) an facultative aerobe
(c) an obligate aerobe
(d) a facultative anaerobe
44. All enzymes of TCA cycle are located in the mitochondrial matrix except one which is located in inner mitochondrial membranes in eukaryotes and in cytosol in prokaryotes. This enzyme is
(a) isocitratedehydrogenase
(b) malate dehydrogenase
(c) succinate dehydrogenase
(d) lactate dehydrogenase.
45. The overall goal of glycolysis, krebs cycle and the electron transport system is the formation of
(a) ATP in one large oxidation reaction
(b) sugars
(c) nucleic acids
(d) ATP in small stepwise units.
46. The energy-releasing process in which the substrate is oxidised without an external electron acceptor is called
(a) fermentation
(b) photorespiration
(c) aerobic respiration
(d) glycolysis
47. In germinating seeds fatty acids are degraded exclusively in the
(a) proplastids
(b) glyoxysomes
(c) peroxisomes
(d) mitochondria
48. The chemiosmotic coupling hypothesis of oxidative phosphorylation proposes that adenosine triphosphate (ATP) is formed because:
(a) high energy bonds are formed in mitochondrial proteins
(b) ADP is pumped out of the matrix into the intermembrane space
(c) a proton gradient forms across the inner membrane
(d) there is a change in the permeability of the inner mitochondrial membrane toward adenosine diphosphate (ADP)
49. Aerobic respiratory pathway is appropriately termed:
(a) parabolic
(b) amphibolic
(c) anabolic
(d) catabolic
50. In which of the following types of respiration, the amount of energy released is comparatively more
(a) Aerobic respiration
(b) Anaerobic respiration
(c) Equal energy is released in both A and B
(d) None of these in correct
51. Which statement is wrong for Krebs’ cycle?
(a) There is one point in the cycle where FAD+ is reduced to FADH2 .
(b) During conversion of succinyl CoA to succinic acid, a molecule of GTP is synthesised.
(c) The cycle starts with condensation of acetyl group (acetyl CoA) with pyruvic acid to yield citric acid
(d) There are three points in the cycle where NAD+ is reduced to NADH+ H+.
52. By which of the following complex, proton is pumped to reach ATP synthase to participate in ATP synthesis?
(a) Cytochrome b6f
(b) Cytochrome a – a3
(c) Cytochrome c oxidase
(d) Cytochrome bc
54. Decarboxylation of pyruvic acid results in the formation of
(a) Water
(b) Acetyl CoA
(c) Glucose
(d) PGA
55. In which one of the following processes CO2 is not released?
(a) Aerobic respiration in plants
(b) Aerobic respiration in animals
(c) Lactate fermentation
(d) Alcoholic fermentation
56. Terminal cytochrome of respiratory chain which donates electrons to oxygen is
(a) Cyt b
(b) Cyt a 1
(c) Cyt c
(d) Cyt a 3
57.Oxidative phosphorylation occurs in
(a) Mitochondria
(b) Chloroplast
(c) Cytoplasm
(d) Golgi bodies
58. Which of the metabolites is common to respiration mediated breakdown of fats, carbohydrates and proteins?
(a) Acetyl CoA
(b) Pyruvic acid
(c) Glucose 6 phosphate
(d) Fructose 1, 6 bisphosphate
59. At a temperature above 35ºC
(a) rate of photosynthesis will decline earlier than that of respiration
(b) rate of respiration will decline earlier than that of photosynthesis
(c) there is no fixed pattern
(d) both decline simultaneously.
60. The energy releasing metabolic process in which substrate is oxidised without an external electron acceptor is called
(a) glycolysis
(b) aerobic respiration
(c) fermentation
(d) photorespiration
61. When amount of CO2 taken from atmosphere (in photosynthesis) becomes equal to the amount of CO2 released in atmosphere (in respiration), this is called
(a) Final point
(b) Compensation point
(c) Balance point
(d) Equal distribution
62. The overall goal of glycolysis, Krebs’ cycle and the electron transport system is the formation of
(a) ATP in one large oxidation reaction
(b) nucleic acids
(c) sugars
(d) ATP in small stepwise units
63. In an organism utilising carbohydrates as its source of energy anaerobically, the R.Q. is likely.
(a) 0.7
(b) 0.9
(c) 1.0
(d) Infinity
64.Pyruvate kinase enzyme catalyses
(a) second irreversible step of glycolysis
(b) first irreversible step of glycolysis
(c) fourth irreversible step of glycolysis
(d) third irreversible step of glycolysis
65. The correct sequence of the three processes of aerobic respiration is
(a) Glycolysis, Kreb’s cycle, oxidative phosphorylation.
(b) Glycolysis, oxidative phosphorylation and Kreb’s cycle
(c) Kreb’s cycle, glycolysis and oxidative phosphorylation
(d) oxidative phosphorylation, Kreb’s cycle, glycolysis
66. Net gain of ATP molecules, during aerobic respiration, is
(a) 36 molecules
(b) 38 molecules
(c) 40 molecules
(d) 48 molecules
67. The correct sequence of electron acceptor in ATP synthesis is
(a) Cyt. c, b, a, a 3
(b) Cyt. b, c, a 3 , a
(c) Cyt. a, a, b, c
(d) Cyt. b, c, a, a 3
68. The 1992 Nobel Prize for medicine was awarded to Edmond H. Fischer and Edwin J. Krebs for their work concerning
(a) isolation of the gene for a human disease
(b) reversible protein phosphorylation as a biological regulation mechanism
(c) human genome project
(d) drug designing involving inhibition of DNA synthesis of the pathogen.
69. Apparatus to measure rate of respiration and R.Q. is
(a) auxanometer
(b) respirometer
(c) manometer
(d) photometer
70. The end product of fermentation are
(a) O2 and C2H5OH
(b) CO2 and acetaldehyde
(c) CO2 and O2
(d) CO2 and C2H5OH
71. Which statement is wrong for Krebs’ cycle ?
(1) There is one point in the cycle where FAD+ is reduced to FADH2
(2) During conversion of succinyl CoA to succinic acid, a molecule of GTP is synthesised
(3) The cycle starts with condensation of acetyl group (acetyl CoA) with pyruvic acid to yield citric acid
(4) There are three points in the cycle where NAD+ is reduced to NADH+ H+
72. Which of these statements is incorrect?
(1) Enzymes of TCA cycle are present in mitochondrial matrix
(2) Glycolysis occurs in cytosol
(3) Oxidative phosphorylation takes place in outer mitochondrial membrane
(4) Glycolysis operates as long as it is supplied with NAD that can pick up hydrogen atoms
73. What is the role of NAD+ in cellular respiration?
(1) It functions as an enzyme.
(2) It functions as an electron carrier.
(3) It is the final electron acceptor for anaerobic respiration.
(4) It is a nucleotide source for ATP synthesis
74. Respiratory Quotient (RQ) value of tripalmitin is
(1) 0.9
(2) 0.7
(3) 0.07
(4) 0.09
75. Conversion of glucose to glucose-6-phosphate, the first irreversible reaction of glycolysis, is catalyzed by
(1) Aldolase
(2) Hexokinase
(3) Enolase
(4) Phosphofructokinase
76. The number of substrate level phosphorylations in one turn of citric acid cycle is
(1) Two
(2) Three
(3) Zero
(4) One
77. Which of the following statements of incorrect?
(1) Oxidation-reducation reactions produce proton gradient in respiration
(2) During aerobic respiration, role of oxygen is limited to the terminal stage
(3) In ETC (Electron Transport Chain), one molecule of NADH + H+ gives rise to 2 ATP molecules, and one FADH2 gives rise to 3 ATP molecules
(4) ATP is synthesized through complex V
Solutions
1.Solution: (b) Glycolysis involves the process of partial oxidation of glucose or similar hexose sugar into two molecules of pyruvic acid through
a series of ten enzyme mediated reactions. It occurs in cytoplasm.
2.Solution: (a) Complete degradation of a molecule of glucose produces 12 molecules of NADPH2 by HMP.
3. Solution: (c) Respiratory Quotient
4. Solution: (b) The end product of glycolysis is pyruvic acid which is a three carbon compound.
5. Solution: (b) Ratio of the volume of CO2 produced to the volume of O2 consumed in respiration over a period of time is known as respiratory
quotient.
6. Solution: (b)The net gain of energy is equal to 8 ATP in EMP pathway.
7. Solution: (d)The end product of glycolysis is pyruvate. It enters mitochondria and is oxidatively decarboxylated to acetyl CoA before entering into Krebs cycle.
8.Solution: (b) 2 ATP are produced during glycolysis in cytoplasm. 34 ATP are produced by Krebs cycle, oxidative phosphorylation, ETC.
9. Solution: (c) Aerobic respiration is an enzymatically controlled release of energy in a stepwise catabolic process of complete oxidation of
organic substrate into CO2 and H2O with O2 acting as terminal oxidant.
10.Solution: (a) The optimum temperature of photosynthesis is 10º–25ºC for C3 plants and 30º–45ºC for C4 plants.
11. Solution: (b) Oxidative phosphorylation is the synthesis of energy rich ATP molecules with the help of energy liberated during oxidation of
reduced co-enzymes produced in respiration. molecules
12.Solution: (c) Historically it was believed that 38 ATP is produced from 38 ADP. But the current estimate is that about 30 molecules of ATP
are formed when glucose is completely oxidised to CO2.
13.Solution: (c) Respirometer is an instrument for measuring respiratory quotient as well as rate of respiration.
14. Solution: (d) Terminal cytochorome is cyt a3. cyt a3 posseses two copper centers. It helps in transfer of electrons to oxygen.
15.Solution: (d) The two molecules of pyruvate are completely degraded in Krebs cycle to form two molecules of ATP, 8 NADH2, 2 FADH2,
CO2 and water.
16. Solution: (a) Complete degradation of a molecule of glucose yields 38 ATP molecules.
17. Solution: (d) In Anaerobic respiration, oxygen is not used in the breakdown of respiratory substrate.
18. Solution: (a) Fats are used as respiratory substrates by a number of organisms because they contain more energy as compared to carbohydrates.
19.Solution: (a) ATP is injected in cyanide poisoning because it is necessary for cellular functions. ATP makes energy available at a spot away from the area of release of energy so it helps in maintaining cellular functions.
20. Solution: (d) End products of fermentation are ethyl alcohol, lactic acid and CO2. 21. Solution: (b) Firstly, amylose and glycogen are
converted to glucose. Deamination of ketogenic amino acids occur and these enter respiratory catabolism as intermediates.
22. Solution: (b) Glycolysis is the first step of respiration which occurs without requirement of O2 and is common to both aerobic and
anaerobic modes of respiration.
23.Solution: (d) During aerobic oxidation of pyruvic acid, first of all there is activation of pyruvic acid in which NAD and coenzyme react with
pyruvic acid and oxidative decarboxylation takes place leading to the formation of acetyl Co-A. In this process, Lipoic acid amide (LAA), thyamine pyrophosphate (TPP) and NAD are essential to perform this reaction.
24.Solution (d) Respiratory quotient (R.Q.) is defined as the ratio of the molecules of carbon dioxide given out to the number of oxygen
molecules taken in during respiration. Its value for fatty acids is always less than unity.
25. Solution: (d) Oxidative phosphorylation is the synthesis of energy rich ATP from ADP and inorganic phosphate, that is connected to oxidation of reduced coenzymes produced in cellular respiration.
26. Solution: (c) Competitive inhibition is the reversible inhibition of enzyme activity due to presence of substrate analogues. Non competitive inhibition is the reduction of enzyme activity by a factor that has no real structural similarity with the substrate. Allosteric inhibition is reversible
noncompetitive inhibition occurring in case of allosteric enzymes. Herein the inhibitors are the products or intermediates of reactions catalyzed by the enzymes. Hence it is also called end product inhibition or feedback inhibition.
27.Solution: (a) The enzyme involved in Krebs cycle are localized in the mitochondrial matrix.
28.Solution: (b) Fermentation is referred to as the decomposition of organic compounds, anaerobically by enzymes yielding alcohol, organic acids; gases etc.
29. Solution: (c) According to the chemiosmotic theory the energy liberated during electron transport performs the osmotic work of accumulating
H+ ions, conserving energy in building a proton gradient, which is used to build ATP from ADP and inorganic phosphate.
30.Solution: (c) In the conversion of succinyl Co A to succinic acid, energy liberated during hydrolysis of succinyl CoA is used in synthesis of GTP. For the conversion of alfa-ketoglutarate to succinyl CoA, NAD+ and CoA are required. Conversion of fumaric acid to malic acid involves simple
hydration. FAD participates in conversion of succinic acid to fumaric acid.
31.Solution: (c) Mesosome. Mesosomes are the invaginations of the plasma membrane that can form into vesicles. They are found to be
present in both gram-positive and gramnegative bacteria. Mesosomes may play arole in cell wall formation during cell division and/or chromosome replication and distribution and/or electron transfer systems of respiration.
32.Solution: (a) The energy yield during aerobic respiration (36 ATP) is 18 times of that during anaerobic respiration (2 ATP).
33.Solution: (a) 38 molecules of ATP produced during aerobic respiration. Of these 2 ATP are used in link reaction. Hence net gain is of 36 ATP.
34. Solution: (c) 38 ATP molecules are produced by aerobic oxidation of glucose.
35. Solution: (b) In alcohol fermentation triose phosphate is the electron donor while acetaldehyde is the electron acceptor.
36.Solution: (c) Lignin is a complex polymer of phenylpropane units, which are crosslinked to each other with a variety of different chemical bonds.
37. Solution: (d) ATP molecules from ADP are generated maximum in electron transport chain.
38. Solution: (c) TCA cycle is so called because the first stable product formed is a tricarboxylic acid molecule that is citric acid. Hence the
name citric acid cycle. It is also called the Krebs cycle.
39.Solution: (c) ATP is the energy currency in all cells. Glyceraldehyde 3 – phosphate is reduced during glycolysis. Molecular oxygen is the
terminal electron acceptor in ETS.
40. Chemiosmotic theory of ATP synthesis in the chloroplasts and mitochondria is based on: [2005]
Solution: (d)
The enzyme responsible for oxidative phosphorylation is ATP synthase. ATP synthase is located in the F1 component of F0 – F1 or elementary particles. ATP synthase becomes active in ATP formation only where there is a proton gradient having higher concentration of H+ or
protons on the F0 side as compared to F1 side. Increased proton concentration is produced in the outer chamber of outer surface of inner mitochondrial memberane by the pushing of protons with the help of energy liberated by passage of electrons from one carrier to another.
41. Solution: (d) ATP molecules from ADP are generated maximum in electron transport chain.
42.Solution: (b) 12 kcal of energy present in one molecule of ATP & on oxidation of one mole of glucose into CO2 and H2O energy released
in 686 kcal. So no. of ATP which can store this energy would be = 57.1 = 57 ATPs.
43.Solution: (a) Clostridium botulinum is an obligate anaerobe i.e. it normally lives in the absence of oxygen. Facultative anaerobes are those who generally live in oxygen but may live without oxygen in suitable medium. Obligate aerobes can only live in the presence of oxygen while facultative aerobes generally live in oxygen but can also live without oxygen.
44.Solution: (c) Succinate:ubiquinone oxidoreductase, also known in mitochondria as Complex II, provides a link between the citric acid cycle
and the membrane-bound electrontransport system. The membrane extrinsic, water-soluble domain, known as succinate dehydrogenase (SDH), contains the fumarate/succinate active site with a covalently bound FAD group and three iron-sulfur clusters: [2Fe-2S]2 +/1+, [4Fe- 4S]2+/1+ and [3Fe-4S]1 +/0. The enzyme catalyzes the interconversion of fumarate and succinate, and is closely related to fumarate reductase
45. Solution: (d) Glycolysis, Krebs cycle and electron transport system, they all give ATP which is the main energy currency of our body.
Glycosis takes place in cytoplasm, Krebs cycle also in cytoplasm and ETS takes place in the mitochondria.
46.Solution: (d) 15Glycolysis takes place in all body cells and is of two types- (a) Anaerobic glycolysisFromglycogen or glucose to lactic acid in
muscles. (b) Aerobic glycolysis- From glycogen or glucose to pyruvic acid (all cells of body)
47.Solution: (b) In germinating seeds, fatty acids are degraded exclusively in the glyoxysomes. Glyoxylate cycle occurs in tissues rich in
fats, such as those of germinating seeds; the enzymes involved in the cycle, which have not been found in mammals, are contained in organelles called glyoxysomes.
48.Solution: (c) Chemiosmotic theory postulated by the British biochemist Peter Mitchell (1920- 22) to explain the formation of ATP in the
mitochondrial electron transport chain. As electrons are transferred along the electron carrier system in the inner mitochondrial membrane, hydrogen ions (protons) are actively transported into the space between the inner and outer mitochondrial membranes, which thus contains a higher concentration of protons than the matrix. This creates an electrochemical gradient across the inner membrane, through which
protons move back into the matrix.
49. Solution: (b) All energy-releasing pathways whether aerobic (requiring oxygen) or anaerobic (not requiring oxygen) begin with a pathway
called glycolysis, which occurs in the cytoplasm (cytosol). Aerobic respiratory pathway is appropriately termed amphibolic. Aerobic respiration is the main energy-releasing pathway leading to ATP formation. It occurs in the mitochondria. Aerobic respiration yields thirty-six ATP.
50.(a) Aerobic respiration is a chemical reaction that transfers energy to cells. The waste products of aerobic respiration are carbon dioxide and water. A major advantage of aerobic respiration is the amount of energy it releases. Without oxygen, organisms can split glucose into just two molecules of pyruvate. This releases only enough energy to make two ATP molecules. With oxygen, organisms can break down glucose all the way to carbon dioxide. This releases enough energy to produce up to 38 ATP molecules. Thus, aerobic respiration releases much more energy than anaerobic respiration.
51.(c) The cycle starts with condensation of acetyl group (acetyl CoA) with pyruvic acid to yield citric acid
52.(a) Cytchrome b6f , proton is pumped to reach ATPs.
54.(b) Pyruvate decarboxylation is an oxidative decarboxylation reaction, or an oxidation reaction where a carboxylate group is removed. This reaction converts pyruvate which was produced through glycolysis to acetyl CoA to be used in the Citric Acid Cycle.
55.(c) Anaerobic respiration or fermentation can be of two types, i.e., lactate fermentation and ethanol fermentation. Lactate fermentation produces lactic acid only as pyruvic acid produced in glycolysis is directly reduced by NADH to form lactic acid and no CO2, is produced. Alcoholic (ethanol) fermentation involves conversion of pyruvate to acetaldehyde, hence, CO2, is released.
56.(d) The EST system contains various electron carries such as cytochromes. The correct sequence of electron carrier/acceptor in ATP synthesis is cyt-b, cyt-c1, cyt-c(a and cyt-a3). Cyt-a3 is the terminal cytochrome, it posses two copper centers, which help in transfer of electron to oxygen.
57.(a) In eukaryotes, oxidative phosphorylation occurs in mitochondria, while photophosphorylation occurs in chloroplaststo produce ATP. Oxidative phosphorylation involves the reduction of O2 to H2O with electrons donated by NADH and FADH2 in all aerobic organisms
58.(a) Carbohydrates are usually first converted into glucose before they are used for respiration. Fats are broken down into glycerol and fatty acids first. If fatty acids were to be respired they would first be degraded to acetyl CoA and enter the pathway. Glycerol would enter the pathway after being converted to 3-phosphoglyceraldehyde (PGAL). The proteins are degraded by proteases to individual amino acids (after deamination) and depending on their structure enter the pathway within the Krebs’ cycle or as pyruvate or acetyl CoA. Thus, acetyl CoA is the common metabolite of all the three (carbohydrates, proteins and fats).
59.(b) The plants can perform photosynthesis on a range of temperature, while some cryophytes can do photosynthesis at 35°C. Usually the plants can perform photosynthesis between 10°C 40° C. The optimum temperature ranges between 25°C 30° C. At high temperature the enzymes are denatured and hence the photosynthetic rate declines
60.(c) Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen.
61.(b) The compensation point is where light intensity is at the point where the rate of photosynthesis is equal to the rate of respiration. At light intensities below this point, more respiration occurs. At higher light intensities, more photosynthesis occurs.
62.(d) Respiration is an energy liberating enzymatically controlled multistep catabolic process of step wise breakdown of organic substances (hexose sugar) inside the living cells. Aerobic respiration includes the 3 major process, glycolysis, Krebs’ cycle and electrons transport chain. The substrate is completely broken down to form CO2 and water. A large amount of energy is released stepwise in the form of ATP.
63. (d) Infinity
64.(d) Pyruvate kinase is the enzyme involved in the last step of glycolysis. It catalyzes the transfer of a phosphate group from phosphoenolpyruvate (PEP) to adenosine diphosphate (ADP), yielding one molecule of pyruvate and one molecule of ATP.
65.(a) Glycolysis, Kreb’s cycle, oxidative phosphorylation.
66. (a) There is net gain of 38 ATP molecules during aerobic respiration of one molecule of glucose. But in most eukaryotic cells, 2 molecules of ATP are required for transporting the NADH produced in glycolysis into the mitochondrion for further oxidation. Hence, net gain of ATP here is 36 molecules.
67.(d) Last step of aerobic respiration is oxidation of reduced co-enzymes, i.e., NADH2, and FADH2, by molecular oxygen through FAD, CoQ (ubiquinone), Cyt. b, Cyt. c,, Cyt. c, Cyt. a and Cyt a. Two hydrogen atoms or electrons move from NADH2, and travel through this ETS chain and finally combine with half molecule of O2, to form water. During this electron transport FAD and Fe of different cytochromes are successively reduced and oxidised and at certain points, enough energy is released which is used to bind ADP with Pi to form ATP.
68. (b) The 1992 Nobel prize for medicine was awarded to edmond H. fischer and Edwin J. Krebs for their work concerning reversible protein phosphorylation as biological regulation mechanism. The winners of 1992 Noble prize in Physiology and Medicine discovered a ‘life switch’ that turns on and off a variety of biological functions of the cell, including the breakdown of fats and the generation of chemical energy. The prize – winning discovery is known as ‘reversible protein phosphorylation’.
69.(b) Respirometer is an instrument used for measuring R.Q and rate of respiration. The most common respirometer is Ganong’s respirometer.
70.(d) When oxygen is not available (anaerobic condition) yeast and some other microbes convert pyruvic acid into ethyl alcohol. It is a two step process. In the first step pyruvic acid is decarboxylated to yield acetaldehyde and CO2.
71.(3) The TCA cycle is a central pathway that provides a unifying point for many metabolites, which feed in at various points. It takes place over eight different steps:
Step 1: Acetyl CoA (two carbon molecule) joins with oxaloacetate (4 carbon molecule) to form citrate (6 carbon molecule).
Step 2: Citrate is converted to isocitrate (an isomer of citrate)
Step 3: Isocitrate is oxidised to alpha-ketoglutarate (a five carbon molecule) which results in the release of carbon dioxide. One NADH molecule is formed. The enzyme responsible for catalysing this step is isocitrate dehydrogenase. This is a rate limiting step as isocitrate dehydrogenase is an allosterically controlled enzyme.
Step 4: Alpha-ketoglutarate is oxidised to form a 4 carbon molecule. This binds to coenzyme A forming succinyl CoA. A second molecule of NADH is produced, alongside a second molecule of carbon dioxide.
Step 5: Succinyl CoA is then converted to succinate (4 carbon molecule) and one GTP molecule is produced.
Step 6: Succinate is converted into fumarate (4 carbon molecule) and a molecule of FADH₂ is produced.
Step 7: Fumarate is converted to malate (another 4 carbon molecule).
Step 8: Malate is then converted into oxaloacetate. The third molecule of NADH is produced.
72(3)Oxidative phosphorylation takes place in the inner mitochondrial membrane, in contrast with most of the reactions of the citric acid cycle and fatty acid oxidation, which take place in the matrix.
73(2) NAD+ is an electron carrier which will pick up electrons during the course of cellular respiration. When NAD+ picks up an electron, it becomes reduced, and becomes NADH. NADH carries electrons all the way to the Electron Transport Chain, where it will then drop off the electrons.
74(2) Respiratory Quotient =
2(C15H98O6)+145O2→102CO2+98H2O+ Energy
RQ =
= 0.7
Respiratory quotient, also known as the respiratory ratio (RQ), is defined as the volume of carbon dioxide released over the volume of oxygen absorbed during respiration. It is a dimensionless number used in a calculation for basal metabolic rate when estimated from carbon dioxide production to oxygen absorption.
75 (2) Hexokinase catalyse the conversion of Glucose to Glucose-6 phosphate. It is the first step of activation phase of glycolysis.
76(4) One
77 (3) In ETC (Electron Transport Chain), one molecule of NADH + H+ gives rise to 2 ATP molecules, and one FADH2 gives rise to 3 ATP molecules
