1. Anaerobic Respiration

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

3. Chemiosmosis couples the electron transport chain to ATP synthesis:

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

5. 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.

6. 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

7. 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

8. 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

9. 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

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

11. 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

12. The Stuff of Life