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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.
• For example, some bacteria, called nitrate
reducers, can transfer electrons to nitrate
(NO3-) reducing it to nitrite (NO2-).
• Less efficient: usually 30-34 ATPs per glucose
molecule.
What happens if there is no available
electron acceptor?
Glucose
2 ADP
glycolysis
2 ATP
2 NAD+
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 eto, 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 PATHWAYS ALLOWS CELLS
TO REGENERATE NAD+ FOR GLYCOLSIS
Fermentation
by-product
Intermediate accepts
electrons from NADH
2 NAD+
2 NADH
2
Pyruvate
Glucose
2 ADP
2 ATP
LACTIC ACID FERMENTATION
OCCURS IN HUMANS
Pyruvate accepts
electrons from NADH
2 Lactate
2 NAD+
2 NADH
2 ADP
2 ATP
Glucose
2 Pyruvate
During heavy exercise, ATP production
will switch from aerobic respiration to
anerobic respiration
ALCOHOL FERMENTATION
OCCURS IN YEAST
2 CO2
2 Ethanol
2 Acetylaldehyde
2 NAD+
2 NADH
Glucose
2 ADP
2 ATP
2 Pyruvate
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