Transcript fates of pyruvate

FATES OF PYRUVATE
-Depends upon presence or absence of O2
- Anaerobic conditions:
1)alcohol fermentation – pyruvate converted to ethyl alcohol
2)lactic acid fermentation - pyruvate converted to lactic acid
(cheese, yogurt)
- Aerobic conditions:
Pyruvate enter the mitochondria where it is completely
oxidized
Pyruvate -> enzyme -> acetyl group + CO2 + NADH
(3C)
(pyruvate
(2C)
dehydrogenase)
From 2 pyruvates:
2 acetyl fragments
2 CO2 exhaled
2 NADH
Acetyl fragment joins Coenzyme A (CoA) and enters Krebs
Cycle in mitochondrial matrix
We end up with what we start off with
1 turn of the cycle
oxidation reactions
decarboxylations
ATP
reduced NADH
reduced FADH2
from glucose
Energy Yield So Far…
• Glycolysis:
– 2 ATP, 2 NADH
• Pyruvate Oxidation:
– 2 NADH, 2 CO2
• Krebs Cycle:
– 2 ATP
– 6 NADH
– 2 FADH2
– 4 CO2
Electron Transport Complexes
• Only 3 sites that can pump protons; II can’t
• Complex I – NADH Dehydrogenase
• Takes H off NADH; conducts e- from NADH to
ubiquinone
• Complex II – succinate dehydrogenase – conducts efrom FADH2 to ubiquinone
• Complex III – cytochrome BC1 – conducts e- from
ubiquinone – cytochrome C
• Complex IV – cytochrome oxidase – conducts e- from
cytochrome – O2, THE FINAL ELECTRON
ACCEPTOR
So far the ATP’s have been generated via substrate level
phosphorylation, now it’s time for chemiosmosis:
Adding up the ATP
•
•
•
•
Glycolysis
Krebs
10 NADH x 3 ATP/NADH
2 FADH2 x 2 ATP/FADH2
2 ATP
2 ATP
30 ATP
4 ATP
Control of ATP Synthesis
• Controlled by energy needs of the cell
• Enzymes in Glycolysis and Krebs
control this