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 (O2) is the final electron acceptor.

What happens if there is no available electron acceptor? Glucose 2 ADP 2 NAD+ glycolysis 2 ATP 2 NADH 2 pyruvate Aerobic respiration: The NADH then passes its high energy e- to the electron transport chain (becoming NAD+ again) and eventually to O2 Anaerobic respiration: Without O2, NADH has nowhere to donate its e- to, NAD+ cannot be regenerated, and glycolysis stops

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

Fermentation by-product 2 NAD+ 2 NADH Glucose 2 ATP 2 ADP FERMENTATION PATHWAYS ALLOWS CELLS TO REGENERATE NAD+ FOR GLYCOLSIS Fermentation by-product Intermediate accepts electrons from NADH 2 NAD+ 2 NADH 2 Pyruvate Glucose Figure: 6.15a Caption: Among the bacteria, archaea, and eukaryotes, many different types of fermentation occur. All result in the regeneration of NAD+, so that glycolysis can continue to produce ATP even when the electron acceptors required by electron transport chains are unavailable. 2 ATP 2 ADP

LACTIC ACID FERMENTATION OCCURS IN HUMANS Pyruvate accepts electrons from NADH 2 Lactate 2 NAD+ 2 NADH Figure: 6.15b Caption: Among the bacteria, archaea, and eukaryotes, many different types of fermentation occur. All result in the regeneration of NAD+, so that glycolysis can continue to produce ATP even when the electron acceptors required by electron transport chains are unavailable. One of the best-studied types of fermentation is shown in part (b). Glucose 2 ADP 2 ATP 2 Pyruvate

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

ALCOHOL FERMENTATION OCCURS IN YEAST 2 Ethanol 2 Acetylaldehyde 2 NAD+ 2 NADH Figure: 6.15c Caption: Among the bacteria, archaea, and eukaryotes, many different types of fermentation occur. All result in the regeneration of NAD+, so that glycolysis can continue to produce ATP even when the electron acceptors required by electron transport chains are unavailable. One of the best-studied types of fermentation is shown in part (c). Glucose 2 ADP 2 ATP 2 Pyruvate

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