PDH/TCA Cycle Flashcards
what is a metabolon?
complex of enzymes that carry out functionally related rxns, improves reaction rates
how do metabolons provide advantages?
through substrate channeling (local substrate concentration can be high even if overall is low)
what are the advantages of a metabolon?
allows intermediates to be transferred directly from one enzyme to another, minimizes diffusion of reactants
what is the key role of PDH?
convert pyruvate into acetyl-CoA
what is PDH made up of and where can you find it?
3 different enzymes tightly associated in one complex, located in mitochondria
what is the PDH rxn step 1?
PDH + TPP carbanion of E1, product undergoes decarboxylation
what is the PDH rxn step 2?
transferred by E1 to E2, redox rxn occurs
what is the PDH rxn step 3?
acetyl group is transferred, produces acetyl-CoA
what is the PDH rxn step 4?
E3 reoxidizes via transfer of 2e-
what is the PDH rxn step 5?
E3 catalyzes e- transfer, is reoxidized to produce NADH
what does TPP stand for?
thiamine pyrophosphate (1 of 5 cofactors used in PDH reaction)
what is TPP responsible for?
PDH decarboxylation of pyruvate (forms carbanion on C atom which attacks pyruvate carbonyl C to form new C-C bond and release CO2)
what is Beriberi?
disease associated with low thiamine levels, low levels reduce TPP and inhibit conversion of pyruvate (Wernicke-Korsakoff is neurological version of this)
what does Beriberi result in?
slow mental rxns and reduced movement
what does acetyl-CoA connect?
connects glycolysis (carbohydrate catabolism) and amino/fatty acid catabolism
what occurs during stage 1 of the TCA cycle?
acetyl Co-A funnels many carbon sources into central pathway
what occurs during stage 2 of the TCA cycle?
acetyl group is added to oxaloacetate to form citrate, other substrates can enter TCA through intermediates
what is the energetic outcome of stage 2 of the TCA cycle?
reduction of 3 NADH and 1 FADH2, 1 ATP, and intermediates
what occurs during stage 3 of the TCA cycle?
reduced electron carriers are oxidized to synthesize more ATP
which TCA reaction is closest to the PDH rxn?
alpha-ketoglutarate dehydrogenase complex
what is the glyoxylate cycle?
how plants convert fat into sugars
what are the four anabolic pathways fueled by TCA?
citrate, alpha-ketoglutarate, succinyl-CoA, oxaloacetate
what does the citrate anabolic pathway produce?
fatty acids, sterols
what does the alpha-ketoglutarate anabolic pathway produce?
glutamate (other AAs, purines)
what does the succinyl-CoA anabolic pathway produce?
heme, chlorophyll
what does the oxaloacetate anabolic pathway produce?
aspartate (other AAs, purines and pyrimidines)
what is the overall goal of the TCA cycle?
generate NADH, FADH2, ATP, and biosynthetic precursors for anabolic pathways
