Download Fate of pyruvate

Introduction of Glucose Metabolism
Lecture-3
Fate of Pyruvate
& Citric Acid Cycle
Fate of pyruvate
1- Lactate (in cytosol)
Enzyme: lactate dehyrogenase (LDH)
in anaerobic glycolysis
2- Acetyl CoA
in mitochondria
Enzyme: pyruvate dehydrogenase
occurs in aerobic glycolysis
Acetyl CoA is required for citric acid cycle (CAC)
3- Oxalacetate
in mitochondria
Enzyme: pyruvate carboxylase
Oxalacetate is required for:
1- Citric acid cycle (condenses with acetyl CoA): to yield energy ATP
OR 2-Gluconeogenesis (to synthesize glucose)
Fate of
Pyruvate
Glucose
glycolysis
Gluconeogenesis
mitochondria
OXALACETATE
No Oxygen
No Mitochondria
OR BOTH
PYRUVATE
Oxygen
&
Mitochondria
ACETYL CoA
CITRIC ACID CYCLE
LACTATE
Formation of acetyl CoA from pyruvate
•
Pyruvate (end product of aerobic glycolysis) is transported into the mitochondria.
•
In the mitochondrial matrix, pyruvate is converted to acetyl CoA by
pyruvate dehydrogenase complex (multienzyme complex)
This reaction is irreversible
•
Pyruvate dehydrogenase complex is composed of three enzymes & five coenzymes
•
Coenzymes of the complex are derived from water soluble vitamins:
1- Thiamine pyruphosphate, TPP (derived from thiamine, vitamin B1)
2- NAD+ (derived from niacin)
3- FAD (derived from riboflavin)
4- Lipoic acid
5- Coenzyme A (derived from pantothenic acid)
Pyruvate dehydrogenase complex
PYRUVATE
ACETYL CoA
Citric acid cycle
or,(Krebs cycle)
Citric Acid Cycle
Citric acid cycle
is the final pathway where the oxidative metabolism of
Carbohydrates (as glucose), proteins (amino acids) & lipids (fatty acids)
to yield energy (ATP)
Acetyl CoA is the end product for oxidation of carbohydrates, lipids & proteins
Acetyl CoA condenses with oxalacetate to form citrate (first reaction of the cycle)
3 NADH are produced = 3 X 3 = 9 ATP (by oxidative phosphorylation)
One FADH2 is produced = 1 X 2 = 2 ATP (by oxidative phosphorylation)
One ATP is produced (by substrate level phosphorylation)
Net = 12 ATP / one acetyl CoA
Citric Acid Cycle CYCLE - SUMMARY
Acetyl CoA
3 NAD
3 NADH + H
2 CO2
1 FAD
1 FADH2
1 ADP
1 ATP
Citric acid cycle
or,(Krebs cycle)