A2 Biology: Anaerobic respiration

• Occurs in the absence of oxygen
• Only consists of glycolyis
• therefore takes place in the cytoplasm
• Net ATP made: 2
• Produces lactate (in animals) or ethanol (in plants) as a waste product.

Only glycolysis occurs as oxygen is the final electron acceptor; without it the ETC cannot function. The reduced NAD is not re-oxidised (lose H) and ergo there is an absence NAD for the Krebs cycle to function. Fungi, such as yeast, use ethanol fermentation and animals use lactate fermentation.

LACTATE FERMENTATION

• Pryuvate (3C) -----lactate dehydrogenase----> Lactate (3C)
                      Reduced NAD -- NAD -- glycolysis
• During this process pryuvate is acting a an aternativ H acceptor
• Lactate is carried away from the muscles to the liver. It is converted back to pryuvate when oxygen is present again.
• Muscle fatigue is not caused by the lactate but the drop in the pH that results from its formation, buffers in muscle help prevent this.

ALCOHOLIC FERMENTATION

• Pryuvate (3C) --pryuvate decarboxylase--> Ethanal (2C) --ethanal dehydrogenase--> Ethanol (2C)
•                                                                  gives out CO2         reduced NAD -> NAD