Anaerobic Respiration

During the last stage of cell respiration, electrons from glucose are passed down the electron passport chain to the final electron acceptor, oxygen

Chemiosmosis couples the electron transport chain to ATP synthesis:

Aerobic Respiration When oxygen is the final electron acceptor, the process is called aerobic respiration Aerobic = occurring in the presence of oxygen

Anaerobic Respiration Some prokaryotes are able to carry out anaerobic respiration, respiration in which an inorganic molecule other than oxygen (O 2 ) is the final electron acceptor. For example, some bacteria, called nitrate reducers, can transfer electrons to nitrate (NO 3 - ) reducing it to nitrite (NO 2 - ). Less efficient: usually ATPs per glucose molecule.

What happens if there is no available electron acceptor? Glucose 2 pyruvate 2 ATP 2 ADP2 NAD + 2 NADH Aerobic respiration: The NADH then passes its high energy e- to the electron transport chain (becoming NAD + again) and eventually to O 2 Anaerobic respiration: Without O 2, NADH has nowhere to donate its e - to, NAD+ cannot be regenerated, and glycolysis stops glycolysis

Anaerobic fermentation Fermentation: An alternative set of reactions that can follow glycolysis in the absence of oxygen as a final electron acceptor. Extremely inefficient: no Kreb’s cycle, no ETC. Glycolysis produces a net of 2 ATP’s per glucose molecule

Glucose 2 Pyruvate 2 NAD + 2 NADH 2 ADP 2 ATP Fermentation by-product Intermediate accepts electrons from NADH FERMENTATION PATHWAYS ALLOWS CELLS TO REGENERATE NAD + FOR GLYCOLSIS

Glucose 2 Pyruvate 2 NAD + 2 NADH 2 ADP 2 ATP 2 Lactate Pyruvate accepts electrons from NADH LACTIC ACID FERMENTATION OCCURS IN HUMANS

During heavy exercise, ATP production will switch from aerobic respiration to anerobic respiration

Glucose 2 Pyruvate 2 NAD + 2 NADH 2 ADP 2 ATP 2 Ethanol 2 Acetylaldehyde 2 CO 2 ALCOHOL FERMENTATION OCCURS IN YEAST

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