oxidation of pyruvate + citric acid cycle

oxidation of pyruvate

after glycolysis, each pyruvate still contains a large amount of energy found in glucose. what happens next depends on the type of cell and if oxygen is present

cell is anaerobic/facultative aerobe + no O2

leads to fermentation

cell is aerobic + O2

pyruvate moves to CAC cycle and ETC

anaerobic cellular respiration

pyruvate must move from cytoplasm, through mitochondrial membranes, and into the matrix. it diffuses through the outer membrane pores, and requires a membrane protein to pass through the inner membrane. once in the matrix, it is oxidized to form an acetyl group, forming acetyl-coA

citric acid cycle

occurs in the matrix of mitochondria, starts and ends with the same molecule (oxaloacetate), the 2nd process of aerobic cellular respiration

acetate + oxaloacetate → citrate

catalyzed by the citrate enzyme

citrate → isocitrate

creation of an isomer

isocitrate → (alpha) ketoglutarate

isocitrate is oxidized, NAD+ is reduced to form NADH + H+, loss of a carbon in the form of CO2, catalyzed by isocitrate dehydrogenase

(alpha) ketoglutarate → succinyl-coA

(alpha) ketoglutarate is oxidized, reducing NAD+ to form NADH + H+, loss of a carbon in form of CO2, catalyzed by (alpha) ketoglutarate dehydrogenase, coA helps stabilize

succinyl-coA → succinate

release of coA, endergonic reaction makes ATP (by SLP), coA goes back to grab another molecule

succinate → fumarate

succinate is oxidized, 2 electrons and 2 protons are removed and transferred to FAD to form FADH2, catalyzed by succinate dehydrogenase

fumarate → malate

addition of a water molecule

malate → oxaloacetate

malate is oxidized, NAD+ is reduced, catalyzed by malate dehydrogenase

summary of CAC

starts and ends with oxaloacetate, CAC spins 2x per glucose (2 pyruvates made from glucose)

net products

8 NADH (4 per pyruvate)
6 CO2 (3 per pyruvate)
2 FADH2 (1 per pyruvate)
2 ATP (1 per pyruvate)