Fermentation

Question 1

Lactic Acid Fermentation

Answer 1

Reversible reduction of pyruvate to lactate, but strongly favors lactate formation
During exercise, lactate builds up in muscles of animals rapidly
Lactate can be transported to the liver for gluconeogenesis
High amount of O2 needed (high recovery time)
Regenerates NAD+ from NADH
No net change in NAD+/NADH
Restores glycogen stores

Question 2

The Cori Cycle

Answer 2

Muscles:
Use ATP produced by glycogen–>pyruvate to contract muscles
Pyruvate–>blood lactate–> lactate (liver)
Liver:
Uses ATP produced by glycolysis in muscles to regenerate glucose during recovery
Lactate–>glucose–>blood glucose–>glycogen

Question 3

Ethanol Fermentation

Answer 3

Irreversible
Uses pyruvate decarboxylase (which humans don’t have–instead, alcohol dehydrogenase)
Pyruvate–(pyruvate decarboxylase)–>Acetaldehyde + CO2–(alcohol dehydrogenase)–>Ethanol
Glucose + 2ADP + 2 P —> 2 EtOH + 2 CO2 + 2 ATP + 2 H2O

Question 4

Pyruvate decarboxylase

Answer 4

Used in ethanol fermentation to reduce pyruvate to ethanol and CO2
Requires 2 cofactors: thiamine pyrophosphate (TPP) and MG2+

Question 5

Thiamine pyrophosphate (TPP)

Answer 5

Cofactor for pyruvate decarboxylation
Vitamin B1
Common acetaldehyde carrier
Pyruvate-->acetaldehyde
"Electron sink": carbanion that readily adds to carbonyl groups when C2 is deprotonated

Question 6

Alcohol dehydrogenase

Answer 6

Requires ZN2+ and NADH
Acetaldehyde–>ethanol
NADH–>NAH+
Requires additional proton from medium to make ethanol