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Fermentation and Control of
Cellular Respiration
AP Biology
Unit 4
Fermentation
• Occurs when there is no oxygen available
• allows some cells to produce ATP without
the use of oxygen
– ATP yield would be lower, though. Do you
know why?
– Only glycolysis is carried out– only 2 ATP
produced.
Fermentation Overview
• Fermentation allows
glycolysis to continue
by producing the
reactants it needs –
NAD+
• Where is the NAD+
usually regenerated
from?
– Electron transport chain–
after the NADH drops
off its electrons.
Types of Fermentation
• Different organisms will carry out different
fermentation processes:
– Alcoholic Fermentation
– Lactic Acid Fermentation
Images taken without permission from http://www.the-voyage.com/kids_new/images/illustrations/find_out/bread_300.jpg and
http://podiatry.curtin.edu.au/encyclopedia/running/running.JPG
Alcoholic Fermentation
• Occurs in yeast
and many bacteria
• End products are
ethanol and NAD+
• Used to make
bread, wine, beer
Lactic Acid Fermentation
• Occurs in certain fungi
and bacteria, and
humans
• End products are lactate
and NAD+
• Lactate is eventually
converted back to
pyruvate in the liver
Aerobic vs. Anaerobic
• Aerobic = requires oxygen
• Anaerobic = does not
require oxygen
• When there is no oxygen
present, fermentation (and
glycolysis) occurs
Versatility
• Glucose is not the only
fuel that can be used in
cellular respiration
• Other biomolecules can
be converted into
intermediates and used in
cellular respiration
Control of Cellular Respiration
• Feedback mechanisms
help regulate cellular
respiration
– Ex. Feedback inhibition
– Phosphofructokinase
(PFK) is the major enzyme
in glycolysis that is
controlled
– ATP, Citrate inhibits
– ADP, AMP stimulates it