How does ethanol inhibit the respiration of yeast?
GROUND:- Yeast respires aerobically when oxygen is available and all the enzymes normally associated with respiration are synthesised by the yeast. However, when oxygen is unavailable (and only when oxygen is unavailable) does yeast turn to anaerobic respiration. In anaerobic respiration (as you know) oxidative phosphorylation (also known as the respiratory chain) on the inner membrane of the mitochondrion is not able to function as there is no oxygen available to accept the protons and electrons at the end of the chain. Therefore, there is a buildup of NADH2 and a shortage of NAD develops. This leads to problems in glycolysis where the shortage of NAD limits the process at the glyceraldehyde phosphate to 1,3-diphosphoglyceric acid point. (Up to this point in glycoslysis 2xATP have been utilised per glucose and no ATP has been produced! NOT a good point to be blocked at!) Yeast therefore takes the pyruvic acid from the end of glycolysis and reduces it to ethanol. This converts NADH2 ba
