medical & biological sciences

Citric Acid Cycle

Start your One-Week Free Trial

Already subscribed? Log in »

Citric Acid Cycle

CITRIC ACID CYCLE (aka Krebs cycle and tricarboxylic acid cycle)

Occurs under aerobic conditions (has many exits and entry points)
Occurs in the mitochondrial matrix (pyruvate transported from cytosol)
First intermediate is Acetyl CoA (two carbon molecule)
8 more intermediates to complete the cycle: Oh, Can I Keep Studying Science For Med-school?

ACETYL CoA

2-carbon molecule
Can come from carbohydrates (via pyruvate), fatty acids and amino acids
Pyruvate dehydrogenase complex: Pyruvate + NAD + --> Acetyl CoA + CO2 + NADH

CITRATE AND ISOCITRATE

6-carbon molecules
Oxaloacetate (4 carbons) + Acetyl CoA (2 carbons) = Citrate
Isomerized to form isocitrate

ALPHA-KETOGLUTARATE

5-carbon molecule
1 carbon dioxide and 1NADH released in its production

SUCCINYL CoA

4-carbon molecule
1 carbon dioxide and 1 NADH released in its production

SUCCINATE

4-carbon molecule
Lost CoA and 1 ATP produced via substrate level phosphorylation

FUMARATE

4-carbon molecule
FADH2 released in its production (F for FADH2 and Fumarate)

MALATE TO OXALOACETATE

Last reaction in the cycle
Both are 4-carbon molecules
Last NADH released in the cycle

TOTAL OUTPUT:

Pyruvate decarboxylation: 1 NADH and 1 carbon dioxide

(x2 per glucose)

Per turn: 2 carbon dioxide molecules, 3 NADH and 2 FADH2

(2 turns per glucose)

NADH and FADH2 deliver electrons to electron transport chain on inner mitochondrial membrane

Related Tutorials