The Fate of Pyruvate

Question 1

The Fate of Pyruvate

Answer 1

1. Can be converted to acetyl CoA, and can be used in a number of metabolic pathways. In the citric acid cycle it is completely oxidized to CO2.
2. Pyruvate can be carboxylated to produce oxaloacetate
3. In some species, Pyruvate can be reduced to ethanol
4. In some species Pyruvate can be reduced to lactate
5. In all species, pyruvate can be converted to alanine

Question 2

Metabolism of pyruvate to Ethanol

Answer 2

• Yeast cells convert pyruvate to ethanol and CO₂ and oxidize NADH to NAD⁺
• First pyruvate is decarboxylated to acetaaldehyde by pyruvate decarboxylase
• Alcohol Dehydrogenase catalyzes the reduction of acetaldehyde to ethanol

Question 3

Reduction of Pyruvate to Lactate

Answer 3

• Reduced to lactate in a reversible reaction catalyzed by lactate dehydrogenase.
• This reaction is common in anaerobic bacteria and also in mammals.
• NAD⁺ is the coenzyme
• This is an oxidation-reduction reaction in which pyruvate is reduced to lactate by transfer of a hydride ion from NADH