Tuesday, January 8, 2008

2 - biochemistry mcqs - 1 to 10 - citric acid cycle

1 - for every FADH2 synthesised by the citric acid cycle , approximately how many number of ATP are produced from the ADP AND PHOSPHATE ?

answer is two .

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2 - which substrates in the citric acid cycle are coupled to the production of NADH ?

answers are ISOCITRATE , ALPHA KETOGLUTARATE AND MALATE .

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3 - the citric acid cycle oxidises the acetyl group of acetyl coA to how many molecules of CO2?

answer is 2 . one molecule of CO2 during the conversion of the isocitrate to alpha ketoglutarate in the presence of the enzyme isocitrate dehydrogenase , and the other during the conversion of the alpha keto glutarate to succinyl co A in the presence of the enzyme alpha keto glutarate dehydrogenase .

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4 - the enzyme which couples the cleavage of the high energy succinyl co-A to the synthesis of a high energy nucleoside triphosphate is ?

answer is SUCCINYL CO A SYNTHETASE .

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5 - the enzyme which catalyses the final reaction of the citric acid cycle regenerating the oxaloacetate is ?

answer is MALATE DEHYDROGENASE .

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6 - The enzyme which catalyses the hydration of a double bond of fumarate to form malate ?

answer is fumarase .

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7 - the enzyme which catalyses the stereospecific dehydrogenation of succinate to fumarate ?

answer is SUCCINATE DEHYDROGENASE.

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8 - in eukaryotes , all the enzymes for the citric acid cycle are located in the ?

answer is MITOCHONDRION .

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9 - lipoyllysyl arm acts as a long tether that swings the disulfide group from E1 to the E 2 active site , and finally to E 3 , where the oxidised disulfide is reduced .

the above statement is FALSE .The reduced disulfide at E3 is reoxidised .

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10 - in addition to pyruvate what are the two additional sources of acetyl co A ?

a- glucose and amino acids
b- amino acids and fatty acids
c- amino acids and glucose
d- glycogen and fatty acids

answer is B . amino acids and fatty acids .

TO VIEW THE CITRIC ACID CYCLE CLICK HERE

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