Anaerobic respiration

1. Anaerobic respiration (anaerobiosis)

2. At the end of aerobic repiration… We’re from Kreb’s cycle! 2H Let’s get together! I’m leaving you!!! Outer mitochondrial membrane 2e- 2H+ We’re very electropositive!!! ½ O2 2H+ H2O 2H+ 2H+ 2H+ 2H+ ATP 2H+ 2H+ 2H+ ADP Inner mitochondrial membrane Intermembrane space

3. Types of anaerobe • Obligate anaerobe • Finds oxygen toxic • “Obliged” to be anaerobic • Facultative anaerobe • Uses anaerobiosis in absence of oxygen • Has “facility” to be anaerobic

4. Yield of anaerobic respiration • Glycolysis only, so 2ATP produced • Also 2 hydrogen atoms removed • But cannot yield ATP due to lack of oxygen • i.e. there is no final electron acceptor in oxidative phosphorylation • No Krebs cycle or electron transport chain (oxidative phosphorylation)

5. What happens to the hydrogen? • H+ions have a lot of free energy • Energy cannot be released without oxygen • Glycolysis must continue so… • H+ is accepted by pyruvate forming… • Lactate or • Ethanol (alcohol)

6. Alcoholic fermentation Ethanal + carbon dioxode Pyruvate CH3COCOOH CH3CHO CO2 Ethanal then combines with H+ ions from NADH NADH + H+ NAD+ Ethanal Ethanol CH3CHO CH3CH2OH

7. Overall C6H12O6 2CH3CH2OH + 2CO2 Glucose Ethanol Carbon dioxode

8. Yeast • Process occurs in yeast • Alcohol produced accumulates around • Eventually reaches a level where toxic to yeast • Kills them • Ethanol cannot be broken down to yield further energy

9. Lactate fermentation • Pyruvate directly accepts the hydrogen atoms from NADH + H+ CH3CHOHCOOH CH3COCOOH pyruvate lactate • Can be further broken down if O2 made • available again • Remaining energy released