Part 1 : Multiple Choice Questions (MCQs) 1)Which of the following statements about Michaelis-Menten kinetics is correct? a)k m, the Michaelis constant, is defined as the concentration of substrate required for the reaction to reach maximum velocity. b) A high Michaelis constant (K m ) indicates a high affinity of an enzyme for its substrate. c) K m, the Michaelis constant, is a measure of the affinity the enzyme has for its substrate. d) K m, the Michaelis constant, is expressed in terms of the reaction velocity. e) The Michaelis constant (K m ) of an enzyme increases when the enzyme concentration is increased. 2)Which of the following statements about the competitive inhibition of an enzyme-catalyzed reaction is correct? a) The V max and K m (Michaelis constant) for a reaction are unchanged in the presence of a competitive inhibitor. b) The V max for a reaction remains unchanged in the presence of a competitive inhibitor. c) The K m for a reaction remains unchanged in the presence of a competitive inhibitor. d) The addition of large amounts of substrate to a reaction cannot overcome the effect of a competitive inhibitor. 3)An uncoupler of oxidative phosphorylation would most likely lead to: a) Inability to oxidise NADH by the electron transport chain. b) Inability to produce heat by the operation of the electron transport chain. c) The electron transport chain continues to oxidise NADH but there is no ATP production and the energy is lost as heat. d)adp provision does affect the electron transport chain when the processes are uncoupled 4)Which of the following statements about the role of the pentose phosphate pathway is correct? a)the pentose phosphate pathway oxidises glucose-6-phosphate completely to carbon dioxide and water. b) The pentose phosphate pathway produces ribose-5-phosphate and NADPH. c) The rate-limiting reaction of the pentose phosphate pathway is catalyzed by transketolase. d) The pentose phosphate pathway occurs in the mitochondria of most cells. 5)Lactate is produced in muscle tissue during anaerobic exercise a) to reoxidise NADH to allow glycolysis to continue b) to provide a substrate for gluconeogenesis in the muscle c) to lower the ph of muscle tissue d) to remove 3-carbon fragments to allow glycolysis to continue 1/9
6)The term 'β-oxidation' refers to the following process: a) the breakdown of triglycerides to fatty acids b) the breakdown of fatty acids to acetyl CoA c) the breakdown of acetyl CoA to CO 2 d) the breakdown of pyruvate to acetyl CoA 7)The number of moles of reduced cofactors produced by the complete oxidation of 1 mol of capric acid (DECANOIC ACID) to CO2 and water will be closest to which of the following? a) 10 moles of FADH2 and 20 moles of NADH.H+ b) 5 moles of FADH2 and 10 moles of NADH.H+ c) 10 moles of FADH2 and 10 moles of NADH.H+ d) 10 moles of FADH2 and 15 moles of NADH.H+ 8)Which one of the following enzymes is involved in the mobilization of fatty acids from triacyglyerol stores in adipose tissue? a) carnitin acyl transferase b) gastric lipase c) hormone sensitive lipase d) lipoprotein lipase e) pancreatic lipase 9)An amino acid that yields acetoacetyl CoA as a final catabolic product of its carbon skeleton would be considered: a) glycogenic b) ketogenic c) glycogenic and ketogenic d) neither glycogenic nor ketogenic e) essential 10)The NH3 produced in muscle degradation of nitrogenated compounds is transported through blood to the liver using as carriers: a) alanine and glutamine b) urea and alanine c) NH4 and glutamate d) Glutamate and glutamine e) Alpha-ketoglutarate and urea 2/9
11)During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase reaction in skeletal muscle must be reoxidized to NAD+ if glycolysis is going to continue. The most important reaction involved in the reoxidation of NADH in anaerobic conditions is: a)dihydroxyacetone phosphate to glycerol 3-phosphate b)glucose 6-phosphate to fructose 6-phosphate c) Isocitrate to a-ketoglutarate d) malate to oxalacetate e) pyruvate to lactate 12) The enzyme that catalyzes this type of reaction belongs to this class of enzymes: a) Class 1: Oxidoreductases b) Class 2: Transferases c) Class 3: Hydrolases d) Class 4: Lyases e) Class 5: Isomerases f) Class 6: Ligases 13)Which of the following statements about the TCA cycle is correct? a) Oxygen is used to oxidise the acetyl group carbons of acetyl-coa in the TCA cycle. b)the TCA cycle produces the water that is formed during the complete oxidation of glucose. c) Oxygen is not used in the TCA cycle, so the cycle can occur in anaerobic conditions. d) Three molecules of NADH and one molecule of FADH2 are produced in one turn of the TCA cycle. 14) All of the following statements are true regarding ETC, except: a) Located in inner mitochondrial membrane b) Components are organized in decreasing orde of redox potential c) Involved with ATP synthesis d) Cyanide inhibits electron flow 3/9
15)Which of the following is correct sequence of processes in the oxidation of glucose? a)krebs cycle - glycolysis - electron transport b)electron transport - Krebs cycle - glycolysis c)glycolysis - Krebs cycle - eletron transport d)krebs cycle - electron transport - glycolysis 16)Which of the following statements about the reactions of glycolysis is correct? a) In glycolysis glucose-6-phosphate is split into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. b) In glycolysis fructose-1:6-bisphosphate is split into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. c)in glycolysis glucose-6-phosphate is isomerized to fructose-1:6-bisphosphate. d)) In glycolysis fructose-6-phosphate is split into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. 17)Which of the following statements about the oxidative decarboxylation of pyruvate is correct? a) The oxidative decarboxylation of pyruvate is catalysed by the enzyme pyruvate decarboxylase. b) The oxidative decarboxylation of pyruvate formed in aerobic glycolysis occurs in the cytosol. c) The oxidative decarboxylation of pyruvate forms acetyl-coa which is fed into the citric acid cycle. d) The oxidative decarboxylation of pyruvate is reversible since there is a large decrease of free energy in the reaction. 18))Muscle glycogen is not available for maintenance of blood glucose concentration because: a) Muscle lacks glucose-6-phosphatase activity b) There is insufficient glycogen in muscle c)muscle lacks glucose transporter GLUT-4 d) Muscle lacks glucagon receptors 19)The primary metabolic fate of lactate released from muscle during intense exercise is: a) Excretion of lactate in urine b) Transported to liver for replenishment of blood glucose by gluconeogenesis c) Conversion to pyruvate d) Gradual reuptake in muscle during the recovery phase following exercise 4/9
20)Rapoport leubering cycle in RBC produces: a) ATP b) NADPH c) 2,3-bisphosphoglycerate d) 1,3-bisphosphoglycerate 21)All of the following statements are true in the transamination of amino acids, except: a) Ammonia is neither consumed nor produced b) Requires pyridoxal phosphate c) The amino group acceptor is α-keto acid d) All amino acids can undergo transamination 22)An example of a transamination process is a)glutamate = hexanoic acid + NH 3 b)aspartate + hexanoic acid = glutamate + oxaloacetate c)aspartate + α ketoglutarate = glutamate + oxaloacetate d)glutamate = α-ketoglutarate + NH 3 23)Which one of the following statements about the urea cycle is FALSE? a) The two nitrogens enter the urea cycle as ammonia and aspartate. b) Urea is produced by the hydrolysis of arginine.. c) Urea is the end product of protein metabolism. d) Urinary urea is increased by a diet rich in protein. e) The urea cycle occurs exclusively in the cytosol. 24)The hormones, epinephrine and glucagon have which one of the following effects on glycogen metabolism in the liver? a) The net synthesis of glycogen is increased. b) Glycogen phosphorylase is phosphorylated and active, whereas glycogen synthase is phosphorylated and inactive. c) Both glycogen phosphorylase and glycogen synthase are activated by phosphorylation but at significantly different rates. d) Glycogen phosphorylase is inactivated by a rise in Ca2+, whereas glycogen synthase is activated. 25)Which one of the following statements concerning gluconeogenesis is correct? a) It occurs in muscle. b) It is inhibited by elevated levels of acetyl CoA. c) It is important in maintaining blood glucose during the normal overnight fast. d) It uses carbon skeletons provided by degradation of fatty acids 5/9
26)Which of the following statements about amino acids is correct? a) Amino acids are classified according to the structures and properties of their side chains. b) Amino acids are uncharged at neutral ph. c) Amino acids in proteins are mainly in the D-configuration. d) Twenty four amino acids are commonly used in protein synthesis. 27)The class of enzymes that split peptide bonds or glycosidic bonds with water is a)hydrolases b)lyases c)transferases d)ligases e)isomerases 28)Which of the following statements about the carbon skeletons of amino acids are correct? Please select all that apply. a) Ketogenic amino acids can give rise to acetyl-coa. b) Ketogenic amino acids give rise to glucose. c)glucogenic amino acids can give rise to glucose in starvation. d)ketogenic amino acids are always converted to ketone bodies. e)some amino acids are both glucogenic and ketogenic 29)If a compound is a competive inhibitor, a)it does not compete for the active site. b)the addition of more substrate does not reverse the inhibition c) the addition of more substrate reverses the inhibition. d)it does not have a structure similar to the substrate 30)Which type of metabolic fuel is utilised for generating glucose under conditions of severe starvation? a) Glycogen. b) Starch c) Amino acids. d) Fats. 6/9
Part II: ESSAY Questions [Answer only FOUR Questions] First Question: i)the following reaction represents the mechanism of action of an uncompetitive inhibitor. (a) Draw a standard Michaelis-Menton curve in the absence and in the presence of increasing amounts of inhibitor. Repeat for a double-reciprocal plot. (b) Explain the results obtained. ii)for a one-substrate, enzyme-catalyzed reaction, double-reciprocal plots were determined for three different enzyme concentrations. Which of the following three families of curve would you expect to be obtained? Explain 7/9
Second Question: Special shuttle systems carry reducing equivalents from cytosolic NADH (rather than NADH itself) into the mitochondria by an indirect route. Explain briefly these systems, indicating their importance. Third Question: The pentose phosphate pathway is an alternative route for the oxidation of glucose. A)Write down the reactions of the Pentose Phosphate Pathway B)Explain the significance of Pentose Phosphate Pathway Fourth Question: Fatty acids are oxidized mainly by a process called -oxidation, It involves following three steps: 1. Activation of fatty acid to acyl-coa 2. Transfer of acyl CoA into mitochondria by carnitine transport system -oxidation in mitochondria Briefly explain each of the above mentioned steps. 4)How many ATPs are produced when palmitoyl- CoA, a 16-carbon saturated fatty acid is oxidized completely to CO2 and H2O? Fifth Question The nitrogen of amino acids removed in the form of ammonia is detoxified by converting it to urea.(urea is the end product of protein metabolism.) A-Explain how ammonia is transported to liver from brain and kidney. Does ammonia producd in muscles proceed the same way? Explain! B- Write down and explain the major steps of Urea synthysis in liver cells. End of Questions Good Luck 8/9
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