Yeast
Undergo
Ethanol
fermentation
Two
step
reduction
of
pyruvate
to
ethanol
0-
CO2
NADH
+
H+
Q
-
Humans
do
not
have
pyruvate
decarboxylase
8
H
NAD+
OM
I-
IP
ic
La
brz
-
O
-
-
Express
alcohol
dehydrogenase
for
ethand
metabolism
pyruvate
I
alcohol
CH3
decarboxylase
CH3
dehydrogenase
CNs
(largely
used
in
reverse
reaction)
Pyruvate
Acetaldehyde
Ethanol
CO2
produced
in
1st
step
is
responsible
for:
Anaerobic
Glycolysis:
fermentation
carbonation
in
beer
Generation
of
energy
(ATP)
without
consuming
oxygen
or
NAD+
Dough
rising
when
baking
bread
Both
steps
require
cofactors
No
net
charge
in
oxidation
state
of
sugars
pyruvate
decarboxylase:
Mg+
thiamine
pyrophosph ate
Reduction
of
pyruvate
to
another
product
alcohol
dehydrogenase:
In*+
NAD
Regenerates
NAD"
for
further
glycolysis
under
anaerobic
conditions
Production
of
food
from
beer,
yogurt,
soy
sauce,
etc
Animals
Undergo
Lactic
Acid
fermentation
Reduction
of
pyruvate
to
lactate,
reversible
Strenuous
exercise,
lactate
builds
up
in
muscle
Ox,
O
NADH
+
H+
Ox
0
I
=
0
NAD
no-
-
-
Generally
1
min
bas
lactate
CH3
dehydrogenase
Acidificatio n
of
muscle
prevents
continuous
strat
pyruvate
L-L ac ta te
Lactate
can
be
transported
to
liver
+
converted
to
glucose
&60
=
-25.1
k)/mol
Requires
a
recovery
time
High
amount
of
O2
consumption
to
fuel
gluconeogenesis
Restores
muscle
glycogen
stores
+Late
2
Pyruvate
