問題詳情

32. Which three reactions catalyzed by the enzymes in the citric acid cycle have large negative AGvalues? Ⅰ.succinyl-CoA synthetase.Ⅱ. fumarase. Ⅲ.α-ketoglutarate dehydrogenase. IV. isocitrate dehydrogenase.V. citrate synthase.Ⅵ. malate dehydrogenase. VII. aconitase. VIII. succinyl-CoA dehydrogenase.
(A) I, III, V
(B) III, IV, V
(C)IV. VI, VIII
(D) I, III, VI
(E) IV, V, VIII

參考答案

答案：B
難度：計算中-1
書單：沒有書單，新增

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＊檸檬酸循環之步驟:pyruvate由細胞質(cytosol)進入粒線體基質(mitochondria)pyruvate+NAD+→acetyl-CoA+CO2+ NADH+ H+(酵素: pyruvate dehydrogenase complex, 消耗1個CO2，產生1個NADH，需要TPP(VitB1)、FAD(VitB2)、NAD+(VitB3)、CoA-SH(VitB5)、lipoate=lipoic acid(擬脂酸=硫辛酸))oxaloacetate(草醋酸=丁酮二酸) +acetyl-CoA→citrate(檸檬酸)+CoA-SH(酵素: citrate synthase)citrate→cis-aconitate (中間過渡物)+H2O(酵素: aconitase，脫去1個H2O)cis-aconitate(中間過渡物)+ H2O→isocitrate(異檸檬酸)(酵素: aconitase，加入1個H2O)isocitrate+NAD+→α-ketoglutarate(α-酮戊二酸)+NADH+ H++CO2(酵素: isocitrate dehydrogenase，消耗1個CO2，產生1個NADH)α-ketoglutarate+NAD+→succinyl-CoA(琥珀醯基輔酶A)+NADH+H++CO2(酵素: α-ketoglutarate dehydrogenase，消耗1個CO2，產生1個NADH )succinyl-CoA+GDP→succinate(琥珀酸)+GTP(酵素: succinyl-CoA synthetase=succinate thiokinase)succinate+FAD→fumarate(胡延索酸)+FADH2(酵素: succinate dehydrogenase，產生1個FADH2)fumarate+ H2O→malate(蘋果酸)(酵素: fumarase，加入1個H2O)malate+NAD+→oxaloacetate(草醋酸=丁酮二酸)+NADH+ H+(酵素: malate dehydrogenase，產生1個NADH)oxaloacetate(草醋酸=丁酮二酸) +acetyl-CoA→citrate(檸檬酸)+CoA-SH(酵素: citrate synthase)