Kreb Cycle

main goal of kreb cycle

main goal is to oxidize Acetyl-CoA (derived from carbohydrates, fats, and proteins) and capture high-energy electrons in the form of:

• NADH

• FADH2

electron carries then fuel the ETC to make ATP

where does kreb cycle happen?

in the mitochondria

pyruvate decarboxlyation

a key metabolic link between glycolysis and the Krebs cycle

• occurs in matrix and converts pyruvate (3C) into Acetyl-CoA (2C) — releasing the first carbon dioxide (CO2) from glucose to metabolism

irreversible and highly regulated, because it’s the committed step into aerobic respiration

pyruvate decarboxlyation (inhibition — downregulation)

• high ATP — indicates high energy status

• high NADH - ETC is backed up

• high Acetyl-CoA — downstream product builds up

• fatty acids — indicate other fuel is available

pyruvate decarboxlyation (activation — upregulation)

• high ADP/AMP — low energy state

• high NAD+ — oxidized state, ETC is active

• high CoA — signals need for more Acetyl-CoA

• calcium — in muscle cells during contraction (signals energy demand)

what enzyme is responsible for pyruvate decarboxlyation

pyruvate dehydrogenase complex

what enters the Kreb cycle?

Acetyl-CoA (2 Acetyl-CoA pre molecule of glucose)

total inputs

• 2 acetyl-CoA

• 6 NAD+

• 2 FAD

• 2 ADP

• 2 Pi

• 2 H2O

total outputs (per glucose)

• 4 CO2

• 6 NADH

• 2 FADH2

• 2 ATP

generates 20 ATP equivalents (via oxidative phosphorylation)

where are most of the carbon (4 per molecules of glucose) lost?

as CO2

what products of the Kreb cycle can be used for anabolic reactions to make cell compounds?

cholesterol, amino acids, heme, and glucose