Lecture 9 Fermentation

Aerobic respiration

Uses O₂ as final electron acceptor, produces ~30-32 ATP

Anaerobic respiration

Uses inorganic molecule (e.g., sulfate) as final electron acceptor, produces H₂S

Fermentation

Uses organic molecule as final electron acceptor, produces 2 ATP via substrate-level phosphorylation only

Alcohol fermentation

Produces ethanol + CO₂

Lactic acid fermentation

Produces lactate

NAD⁺ role in fermentation

Regenerated to keep glycolysis running

NADH regeneration without O₂

NADH donates electrons to organic molecule (pyruvate or acetaldehyde)

Fats catabolism

Broken into glycerol (→ G3P) and fatty acids (→ acetyl CoA)

Proteins catabolism

Broken into amino acids, must undergo deamination first

Phosphofructokinase (PFK)

Pacemaker enzyme that controls first committed step of glycolysis

PFK stimulation

Low ATP (high AMP)

PFK inhibition

High ATP or high citrate

First committed step of glycolysis

Fructose-6-phosphate → Fructose-1,6-bisphosphate (catalyzed by PFK)

Oxidative phosphorylation

ATP made via electron transport chain and chemiosmosis (~26-28 ATP)

Chemiosmosis

Protons flow down concentration gradient through ATP synthase, turning it like a turbine

Substrate-level phosphorylation

Direct ATP transfer from a substrate (only method used in fermentation)

Obligate anaerobe

Cannot survive in presence of O₂

Facultative anaerobe

Can survive using fermentation OR cellular respiration

Final electron acceptor in aerobic respiration

Oxygen (O₂)

Final electron acceptor in alcohol fermentation

Acetaldehyde

Final electron acceptor in lactic acid fermentation

Pyruvate