Cellular Respiration Do Now: 1. Fermentation does not produce any additional ATP. Why might a cell do it, if it doesn’t produce useful energy?

Fermentation: To recycle NAD + Alcoholic Fermentation The top section is glycolysis. The bottom is ethanolic fermentation. Ethanol and CO 2 are the waste products

Redox: LEO the Lion Says GER. The Loss of Electrons is Oxidation; the Gain of Electrons is Reduction. Whenever something is oxidized, something else must be reduced (i.e. the electrons have to go somewhere!) In fermentation, NADH is oxidized, and pyruvate is reduced.

Lactic Acid Fermentation – you do this! Notice: No CO 2 produced. NADH is oxidized to NAD + Pyruvate is reduced to lactic acid.

Fermentation is Wasteful The products of fermentation (ethanol or lactic acid) contain MORE energy than pyruvate! The NADH used loses valuable energy – in anaerobic conditions anyway.

So Why Do They Do it? The electrons ripped from food have to go somewhere! In aerobic respiration they eventually end up in water after being attached to oxygen. When there’s no oxygen around, the cell deposits the electrons on what’s available: the leftovers from glycolysis. This is ONE of the ways in which aerobic respiration is more efficient than anaerobic.

Yummy Yummy Fermentation In addition to making lots of yummy food products from soy sauce to kimchi, fermentations done by engineered microbes can produce useful enzymes or drugs!

Recap Fermentation is the second step in anaerobic respiration; its function is to recycle the NAD+ needed for glycolysis to continue. Alcoholic fermentation (like done by yeast) produces CO 2 and ethanol. Lactic acid fermentation (like done by human muscle cells) produces lactic acid. There are many other types as well. Fermentation is inefficient: the waste products of glycolysis are REDUCED by NADH, which adds chemical energy to them.