Not an intermediate product of citric acid cycle is:
Ans. a. Acetyl Co-A (Ref: Harper's 29/e p165)Acetyl Co-A is a starting molecule, not an intermediate product of citric acid cycle.Citric acid cycle or Krebb's Cycle or TCA cycleCitric acid cycle is a series of reaction in mitochondriaQ that oxidize acetyl CO-A and reduce coenzyme that upon reoxidation are linked to the formation of ATP.Inhibitors of TCA eyeletAconitase which isomerizes citrate to isocitrate, is non competitively inhibited by a rat poison fluoroacetateQ. Fluoroacetate (with acetyl CoA) is converted to fluoroacetyl CoA. which condenses with oxaloacetate to formQ fluoro-citrate - a potent non competitive inhibitor of aconitase - resulting in citrate accumulation.Alpha ketoglutarate dehydrogenase enzyme (which converts a-ketoglutarate tosuccinyl CoA by oxidative decarboxylation) is non-competitively inhibited by arsenite (trivalent arsenic) causing the substrate alpha ketoglutarate to accumulate. Arsenite forms a stable complex with thiol group of lipoic acid making it unavailable to serve as a coenzyme.Oxidation of succinate to fumarate by succinate dehydrogenase is competitively inhibited by malonate. Succinate dehydrogenase is the only enzyme of TCA cycle that is embedded in inner mitochondrial membrane and so also functions as complex II of electron transport chain.Hyperammonemia (| NH3) usually due to urea cycle defect inhibits TCA cycle by depleting a-ketoglutarateQ.Inhibitor of TCA cycleEnzymeInhibition TypeFluoroacetate (Rat poison)AconitaseQNon-competitiveArsenite (Trivalent Arsenic)Alpha-ketoglutarate dehydrogenaseNon-competitiveMalonateSuccinate dehydrogenaseQCompetitiveAmmonia IntoxicationBy depleting Alpha-ketoglutarateQ 4-B Complex Vitamins are Essential in the TCA (Citric Acid) CycleRiboflavinQ (B2)NiacinThiamineQ (B1)Pentothenic acid* In the form of FAD, a cofactor in* a- ketoglutarate dehydrogenase complex succinate dehydrogenase.* In the form of NAD, the electron acceptor coenzyme for three dehydrogenase:* Isocitrate dehydrogenase* a- ketoglutarate dehydrogenase* Malate dehydrogenase* As thiamine diphosphate (TDP/TPP), coenzyme for decarboxylation in a- ketoglutarate dehydrogenase reaction.* As part of coenzyme* A, the cofactor attached to active carboxylic acid residue such as acetyl CoA and succinyl CoA.
Acyl Co-A
Succiny1 Co-A
Citrate
a-ketoglutarate
Kerbs Cycle