Lecture 7

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Fig. 7-2a, p.108
a All carbohydrate breakdown pathways
start in the cytoplasm, with glycolysis.
b Fermentation pathways
are completed in the semifluid
matrix of the cytoplasm.
c In eukaryotes, aerobic
respiration is completed
inside mitochondria.
Fig. 7-2b, p.108
Cytoplasm
glucose
2 ATP ATP
GLYCOLYSIS
4 ATP
(2net)
ATP
2 NADH 2 pyruvate
a The first stage, glycolysis, occurs
in the cell’s cytoplasm. Enzymes
convert a glucose molecule to 2
pyruvate for a net yield of 2 ATP.
During the reactions, 2 NAD+ pick
up electrons and hydrogen atoms,
so 2 NADH form.
Mitochondrion
Krebs
Cycle
6
ATP
CO
2 ATP
2
8 NADH, 2 FADH2
ATP
oxygen
Electron Transfer
Phosphorylation
32 ATP
b The second stage, the Krebs cycle
and a few steps before it, occurs
inside mitochondria. The 2 pyruvates
are broken down to CO2, which leaves
the cell. During the reactions, 8 NAD+
and 2 FAD pick up electrons and
hydrogen atoms, so 8 NADH and 2
FADH2 form. 2 ATP also form.
c The third and final stage, electron
transfer phosphorylation, occurs
inside mitochondria. 10 NADH and 2
FADH2 donate electrons and hydrogen
ions at electron transfer chains.
Electron flow through the chains sets
up H+ gradients that drive ATP
formation. Oxygen
Fig. 7-3, p.109
glucose
2 ADP
(net)
Glycolysis
2 pyruvate
to second stage of
aerobic respiration
or another pathway
2 NADH
to third stage of
aerobic respiration
or another pathway
Fig. 7-4b, p.110
outer membrane
(next to cytoplasm)
glucose
(glycolysis)
2 pyruvate
OUTER COMPARTMENT
inner membrane
inner
mitochondrial
compartment
outer mitochondrial
compartment (in
between the two
membranes)
a An inner membrane divides a
mitochondrion’s interior into two
compartments. The second and third
stages of aerobic respiration take
place at this membrane.
2 acetyl–CoA
CO2
ATP
NADH
Krebs
Cycle
FADH2
INNER COMPARTMENT
Breakdown of 2 pyruvate to
6CO2 yields 2 ATP. Also, 10
coenzymes are reduced (8
NADH, 2 FADH2). The
coenzymes carry hydrogen
ions and electrons to sites
of the third stage of aerobic
respiration.
b The second stage starts after membrane proteins
transport pyruvate from the cytoplasm, across
both mitochondrial membranes, to the inner
compartment. Six carbon atoms enter these
reactions (in two pyruvate), and six leave (in
six CO2). Many coenzymes form.
Fig. 7-5, p.112
Fig. 7-6, p.113
glucose
Glycolysis
you
are
here
Krebs
Cycle
Electron Transfer
Phosphorylation
Fig. 7-6b, p.113
Fig. 7-7, p.114
glucose
Glycolysis
you
are
here
Krebs
Cycle
Electron Transfer
Phosphorylation
Fig. 7-7a, p.114
glucose
2 ATP
Glycolysis
ATP (2 net)
2 NAD+
2 NADH
2 pyruvate
CYTOPLASM
OUTER MITOCHONDRIAL
COMPARTMENT
2 NADH
2 CO2
2 NADH
6 NADH
2 FADH2
INNER MITOCHONDRIAL
COMPARTMENT
2 acetyl-CoA
4 CO2
Krebs
Cycle
2 ATP
ADP + Pi
Electron Transfer
Phosphorylation
H+
water
H+ H+
H+
32 ATP
H+
oxygen
Fig. 7-8, p.115
Fig. 7-9, p.116
Fig. 7-10a, p.117
Fig. 7-11, p.117
FOOD
fats
fatty acids
COMPLEX CARBOHYDRATES
glycerol
glucose, other simple sugars
PROTEINS
amino acids
acetyl-coA
acetyl-coA PGAL
Glycolysis
NADH pyruvate
oxaloacetate
or another
intermediate
of the Krebs
Krebs
Cycle
NADH, FADH2
Electron Transfer
Phosphorylation
Fig. 7-12a, p.119
sunlight
energy in
Photosynthesis
Driven by energy input from
the sun, electrons and hydrogen
are used to form ATP. ATP
energy drives the synthesis of
glucose from hydrogen, electrons
(delivered by coenzymes), and
carbon dioxide’s atoms.
glucose
(stored
chemical
energy)
carbon
dioxide,
water
Aerobic Respiration
Energy input from two ATP
initiates three stages of
reactions. Many ATP form
during thecomplete
breakdown of
glucose to carbon dioxide
and water.
chemical energy in
many ATP available
to drive nearly all
cellular tasks
oxygen
energy out (heat)
energy out (heat)
Fig. 7-13, p.120
1 glucose
ATP (net)
Glycolysis
pyruvate
NADH
Krebs
Cycle
ATP
CO2
FADH2
Electron Transfer
Phosphorylation
ATP
p.122
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