Anaerobic respiration

1
Anaerobic respiration

• Respiration without oxygen

2
Anaerobic respiration

• With no oxygen oxidative phosphorylation and
  Krebs cycle cannot take place. (Cells without
  mitochondria cannot respire aerobically e.g.
  red blood cells)
• In anaerobic respiration glycolysis takes place
  as usual yielding pyruvate and a small amount of
  ATP.
• If pyruvate levels were allowed to build up it
  stop glycolysis and inhibit ATP production, also
  the reduced NAD produced must be oxidised back or
  else the cell would run out of it again
  stopping ATP production.

3
Anaerobic respiration

• Two solutions to this problem
• Alcoholic fermentation used by fungi and plants
• Lactic fermentation used by animals

4
Anaerobic respiration

• Alcoholic fermentation
• Yeasts convert pyruvate to ethanol

5
Anaerobic respiration

• glucose

Producing ethanol from pyruvate regenerates
oxidised NAD and allows glycolysis to continue
triose phosphate oxidised NAD reduced NAD
pyruvate
reduced oxidised NAD NAD
ethanal ethanol
alcohol dehydrogenase
6
Anaerobic respiration

• First CO2 is removed from pyruvate to produce
  ethanal.
• Alcohol dehydrogenase converts ethanal to ethanol
  by adding hydrogen taken from reduced NAD.
• Process used by humans for many thousands of
  years to produced risen breads and alcohol for
  drinking.

7
Anaerobic respiration
8
Anaerobic respiration

• Respiration without oxygen
• in animals (including humans)

9
Anaerobic respiration

• glucose

Producing lactate from pyruvate regenerates
oxidised NAD and allows glycolysis to continue
triose phosphate oxidised NAD reduced NAD
pyruvate
reduced oxidised NAD NAD
lactate
lactate dehydrogenase