6B: Anaerobic Fermentation

Question 1

Anaerobic Fermentation

Answer 1

a metabolic pathway that occurs in the absence of O2. Involves glycolysis, followed by further reactions that convert pyruvate into lactic acid in animals or ethanol and CO2 in yeasts

- The electron transport chain and Krebs cycle are disrupted under anaerobic conditions, losing a key source of ATP
- Consists of just glycolysis generating 2 ATP which recycles NADH from a steady supply of NAD+
- In order to rely indefinitely off glycolysis, cells need a way to convert NADH back to NAD+ without O2

Question 2

Lactic Acid Fermentation

Answer 2

the process of anaerobic fermentation in animals where pyruvate produced via glycolysis is converted to lactic acid

• C6H12O6 -> 2 C3H6O3 + 2 ATP

Question 3

Lactic Acid:

Answer 3

a 3-carbon molecule that is the product of anaerobic fermentation in animals

- Cannot accumulate indefinitely as it lowers the PH of our cells and blood
- Once oxygen is present, lactic acid is metabolised back into pyruvate to be used for aerobic cellular respiration

Question 4

Process of Lactic Acid Fermentation:

Answer 4

• glycolysis occurs where glucose is broken down into two pyruvates
• causes at the same time ADP+Pi to resynthesize into ATP and causes NAD+ resynthesize into NADH
• the 2 pyruvates are then broken down further into 2 lactic acid molecules
• this process requires NADH to unload turning it into NAD+

Question 5

Ethanol Fermentation

Answer 5

the process of anaerobic fermentation in yeasts where pyruvate produced via glycolysis is converted to ethanol and carbon dioxide

• C6H12O6 -> 2 C2H5OH + 2 CO2 + 2 ATP

Question 6

Process of Ethanol Fermentation

Answer 6

• glycolysis occurs where glucose is broken down into two pyruvates
• causes at the same time ADP+Pi to resynthesize into ATP and causes NAD+ resynthesize into NADH
• the 2 pyruvates are then converted into 2 acetyl-CoA molecules producing 1 waste CO2 molecule
• the acetyl-CoA molecules are then converted into 2 ethanol molecules
• this process requires NADH to unload its high energy electrons turning it into NAD+