Tuesday, January 8, 2008

3 - biochemistry mcqs - 11 to 20 - citric acid cycle

11 - citrate has the ability to inhibit this enzyme by competing with oxaloacetate ?

answer is CITRATE SYNTHASE .

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12 - The molecule which inhibits isocitrate dehydrogenase ?

answer is CALCIUM . Ca +2.

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13 - this molecule regulates the citric acid cycle at many points , including the activation of pyruvate dehydrogenase phosphatase , isocitrate dehydrogenase and alpha ketoglutarate dehydrogenase .

answer is SERINE .

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14 - In e coli , this enzyme is inactivated by the phosphorylation of a serine residue in the active site ?

answer is isocitrate dehydrogenase .

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15 - covalent modification of E 1 occurs by the specific phosphorylation of WHICH residue in a reaction catalysed by pyruvate dehydrogenase kinase ?

answer is ATP .

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16 - various dicarboxylates ( alpha ketoglutarate , succinate and malate ) and a tricarboxylate ( citrate ) are rapidly oxidised by muscle tissue during respiration.

this statement is true .

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17 - which citric acid cycle intermediate can be used for the synthesis of porphyrins ?

a - succinate
b- succinyl co A
c- fumarate
d- malate

answer is b .

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18 - which possess the enzymes that mediate the net conversion of acetyl co A to oxaloacetate , which can be used for gluconeogenesis .

answer is PLANTS OR GLYOXYSOMES .

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19 - Which is the cofactor that is the substrate for E 3 and is reduced by FADH2?

Answer is NAD+

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20 - The citric acid cycle acts as a multistep catalyst that can oxidize an unlimited number of ______ groups ?

answer is acetyl groups .

TO VIEW THE CITRIC ACID CYCLE CLICK HERE

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