NOTES: Ch. 9 Part 4 - 9.5 & 9.6 - Fermentation & Regulation of Cellular Respiration
9.5 - Fermentation enables some cells to produce ATP without the use of oxygen
● Cellular respiration
● Glycolysis can produce ATP
(in aerobic or anaerobic conditions)
● In the absence of O2, glycolysis couples with fermentation to produce ATP
 aerobic:
 anaerobic:
 fermentation:
catabolism of organic nutrients
Types of Fermentation
● Fermentation consists of glycolysis plus
, which can be
reused by glycolysis
● Two common types are alcohol fermentation and lactic acid fermentation
Alcoholic Fermentation
chemical equation:
● pyruvate is converted to
● NADH is oxidized to
(recycled)
● performed by
● In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO 2
● Alcohol fermentation by yeast is used in
,
, and
Lactic Acid Fermentation
chemical equation:
● pyruvate is reduced to
● NADH is oxidized to
(
);
(
)
● Lactic acid fermentation by some fungi and bacteria is used to
● Human muscle cells use lactic acid fermentation to
Fermentation and Cellular Respiration Compared:
● Both processes use glycolysis to
and other organic fuels
● in fermentation, NADH is recycled back to
● in fermentation, final electron acceptor is
,
● amount of energy harvested:
Fermentation =
Cellular respiration =
● oxygen
for fermentation
 Obligate anaerobes: only grow in
of oxygen (e.g.
 Obligate aerobes: only grow in
)
of oxygen
 Facultative anaerobes: can grow in either presence or absence of oxygen
(e.g.
)
*in a faculatative anaerobe, pyruvate is a “fork” in the metabolic road which leads to 2 alternate catabolic routes:
-
: Krebs and E.T.C.
-
: Fermentation
The Evolutionary Significance of Glycolysis
● Glycolysis occurs in nearly all organisms
● Glycolysis probably
before there was oxygen in the atmosphere
9.6 - Glycolysis and the Krebs cycle connect to many other metabolic pathways
● Gycolysis and the Krebs cycle are major intersections to various catabolic and anabolic pathways
The Versatility of Catabolism
● Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration
● Glycolysis accepts
● Proteins must be
; amino groups can feed glycolysis or the
Krebs cycle
● Fats are digested to
generating
(
) and
(used in
)
● An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate
Biosynthesis (Anabolic Pathways)
● The body uses small molecules to build other substances
● These small molecules may come
, from
, or from the
Regulation of Cellular Respiration via Feedback Mechanisms
● FEEDBACK INHIBITION is the most common mechanism for control
● If ATP concentration begins to drop,
● when there is plenty of ATP,
● Control of catabolism is based mainly on regulating the
;