Anaerobic Respiration

Anaerobic RespirationWill take place if there is no free oxygen

Because there will be no final hydrogen acceptor

So the ETC cannot take place

So there is no oxidative phosphorylation to form ATP

Glucose is converted to Pyruvate in glycolysis

NAD is reducedThere is a net production of 2 ATP

NAD must be recycled - There are two alternate pathways

Ethanol pathway Lactate pathway

Ethanol Pathway/ Alcoholic

Fermentation

This occurs in some plants (facultative anaerobes) and in yeast

It takes place in the cytoplasm

Glycolysis occurs in the cytoplasm

ATP is being made, even though it is in a small amount

NAD is reduced and must be recycled

Pyruvate will accumulate unless it is removed

Pyruvate is decarboxylated to ethanal

The CO2 given off here is what makes bread rise when dough is mixed with yeast

Ethanal is reduced to Ethanol using hydrogen from NADredThe enzyme required for this process is Alcohol dehydrogenaseNAD can now be reused and glycolysis can continue producing ATP

The fermentation process is used to make alcoholic beverages

The Lactate PathwayThis occurs in mammalian skeletal muscles during exertion

When pyruvate from glycolysis is produced faster than it can be oxidised in the Krebs cycle

This is because the supply of oxygen cannot meet the demand

Glycolysis occurs in the cytoplasm

ATP is being made, even though it is in a small amount

NAD is reduced and must be recycled

Pyruvate will accumulate unless it is removed

Pyruvate acts as the Hydrogen acceptorIt accepts hydrogen from NADred

Pyruvate is converted to lactate by lactate dehydrogenaseNAD available to be reduced again in glycolysis

Pyruvate does not accumulate

ATP is made in small amounts by glycolysis

The skeletal muscles can continue to work

Lactate is toxic and must be removedThis pathway can be reversed but needs oxygen

An oxygen debt therefore exists

Lactate is carried in the blood from the muscles to the liver

20% is oxidized to CO2 and H2O, 80% is converted to glycogen and stored