ANS 330 Citric Acid Cycle

What is pyruvate converted to?

pyruvate is converted to acetyl-CoA, intracellular conditions favor catabolism of pyruvate

What is Acetyl-CoA?

major fuel for CAC (citric acid cycle)

What is pyruvate dehydrogenase?

enzyme that catalyzes pyruvate to acetyl-CoA, NAD+ to NADH and H+, HS-CoA to CO2

What happens during the PDH (pyruvate dehydrogenase) reaction?

NAD+ reduced to NADH and CO2, original glucose molecule now catabolized to two 2-C units

How is the CAC the hub of all aerobic metabolism?

Acetyl-CoA is the common metabolite of CHO, Fat, and Protein

How is citrate formed?

Citrate is formed from oxaloacetate (OAA) and acetyl-CoA, 6-C molecule, enzyme involved is citrate synthase

What is citrate synthase?

it is an important regulatory enzyme of CAC

What is citrate synthase inhibited by?

ATP, NADH, Succinyl-CoA, Acyl-CoA, derivatives of fatty acids, high citrate levels, low OAA

What is citrate then converted to?

Isocitrate

What happens during the isocitrate reaction?

isocitrate is converted to alpha-ketogluterate via isocitrate dehydrogenase, oxidative decarboxylation (C is lost by CO2 production), CO2 and NADH produced

What is isocitrate dehydrogenase inhibited by?

ATP, NADH, muscle fiber has high energy stores

What happens during the alpha-ketogluterate reaction?

alpha-ketogluterate is converted to Succinyl-CoA via alpha-ketogluterate dehydrogenase, oxidative decarboxylation, NADH and CO2 produced

What happens during the Succinyl-CoA reaction?

Succinyl-CoA is converted to succinate via succinyl-CoA synthetase, CoA-SH released, GTP formed, GTP is then quickly converted to ATP

What happens during the succinate reaction?

Succinate is converted to fumarate via succinate dehydrogenase which is another key regulatory point in CAC

What occurs during the succinate dehydrogenase reaction?

FAD is reduced to FADH2, activity responds to exercise training, important regulatory role during exercise

What is fumarate converted to?

Fumarate is converted to malate via fumerase

What happens during the malate reaction?

malate is converted to oxaloacetate via malate dehydrogenase, NADH formed (3rd place NADH is formed)

How many times will the cycle turn?

the cycle will turn 2 times for every glucose molecule catabolized

What are the products of CAC?

3 NADH, 1 FADH2, 2 CO2, 1 ATP

What is the overall reaction for each molecule of acetyl-CoA?

Acetyl-CoA + ADP + 3 NAD + FAD --> 2 CO2 + ATP + 3 NADH + 3H+ + FADH2

What are the two regulatory enzymes for the Kreb's cycle?

citrate synthase, succinate dehydrogenase