The Citric Acid Cycle

Harvesting of high-energy electrons from carbon fuels

4-carbon compound condenses w/ 2-carcon acetyl unit to yield a 6-carbon tricarboxylic acid -> releases co2 twice in 2 oxidative decarboxylations that yield high-energy electrons.4 carbon compound remains -> processes to regenerate oxaloacetate, which can iniate another round of the cycle.2 carbon atoms enter as acetyl unit and 2 leave as co2.

Nope. it removes electrons from acetyl CoA and uses them to reduce NAD+ and FAD to NADH and FADH2. 3 hydride ions (6 electrons) are transferred to 3 mc of NAD+ and 2 H atoms (2 e-) transferred to 1 mc of FAD. e- released flow thru ETC to create a proton gradient. Protons flow thru atp synthase to gen ATP from ADP and Pi. Electrons yield 9 ATP when they are oxidized by O2 in oxidative phosphorylation.

Citric acid cycle in conjunction with oxidative phosphorylation because cit acid can make a lot of NADH and FADH2 and reuses oxaloacetate

Pyruvate +coA + NAD+ --> acetyl CoA + CO2 + NADH + H+ (irreversible)

Acetyl CoA + CO2 + NADH + H+pyruvate dehydrogenase complex produces CO2 and captures e- with NADH. Therefore, the py dehyd rxn has many key features of citcidcyc

Has 3 distinct enzymes (1 does oxidative decarbox of pyruvate, 1 transfers acetyl group to CoA, 1 regenerates the oxidized form of lipoamidE)

Req 3 enzymes and 5 coenzymes. consists of decarboxylation, oxidation, and transfer of resulatant acetyl group to CoA

Pyruvate combines with TPP and then decarboxylated to yeild hydroxyethyl_tPP. the rate limiteding step, catalyzed by first pyruvate dehydrogenase componenet

Hydroxyethyl group attached to TPP is oxidized to form acetyl group and transferrred to lipoamide. cat by 1st py dehyd componentyields acetyllipoamide

Acetyl group transferred from acytyllicpoamide o CoA --> acetyl CoA. cat by E2

Py dehydr cannot complete another cat cycle until dihydrolipoamide is oxidized to lipoamide. 2 e- are transferred tp FAD prosthetic group of the enzyme and then to NAD+

Unusual bc common role of FAD is to recieve e- from NADH

Is regulatd, comprised of multiple copies of E! E2 E3 uses TPP and lipoamide etc. as cofactors, a C from pyruvate is removed as CO2, a NADH is generated

Is unphosphorylated