Anaerobic Respiration

Rucete ✏ Biology In a Nutshell

1. What is Anaerobic Respiration?

• A type of respiration that occurs without oxygen.
• Distinguishing Feature: Unlike aerobic respiration, it does not use oxygen as the final electron acceptor in the electron transport chain.
• When Oxygen is Absent:
  • The electron transport chain stops, causing NADH to accumulate.
  • The Krebs cycle cannot continue.
  • Fermentation regenerates NAD⁺, allowing glycolysis to continue.

2. Types of Anaerobic Respiration

1. Alcohol Fermentation

• Occurs in: Plants, fungi (e.g., yeast), and some bacteria.
• Process:
  1. Pyruvate is converted into acetaldehyde.
  2. Acetaldehyde is reduced by NADH, forming ethanol and CO₂.
  3. NADH is oxidized to regenerate NAD⁺, enabling glycolysis to continue.
• Equation: $$\text{Pyruvate} \rightarrow \text{Acetaldehyde} + CO_2$$$$\text{Acetaldehyde} + NADH \rightarrow \text{Ethanol} + NAD^+$$

2. Lactic Acid Fermentation

• Occurs in: Human muscle cells under low oxygen conditions (e.g., intense exercise).
• Process:
  1. Pyruvate is directly reduced by NADH into lactic acid (lactate).
  2. NADH is oxidized to regenerate NAD⁺, allowing glycolysis to continue.
• Equation: $$\text{Pyruvate} + NADH \rightarrow \text{Lactate} + NAD^+$$

3. Differences Between Alcohol & Lactic Acid Fermentation

Type	Occurs In	End Products	CO₂ Produced?
Alcohol Fermentation	Yeast, Bacteria	Ethanol + CO₂	Yes
Lactic Acid Fermentation	Human Muscle Cells	Lactic Acid	No

4. Why is Fermentation Important?

• Allows ATP production to continue in the absence of oxygen.
• Regenerates NAD⁺ so that glycolysis can continue producing ATP.
• Lactic acid buildup in muscles leads to fatigue and soreness, but can be reversed when oxygen is available.

Anaerobic Respiration In a nutshell

• Alcohol Fermentation = Yeast → Ethanol + CO₂
• Lactic Acid Fermentation = Muscles → Lactic Acid (No CO₂)