Cell Respiration-Introduction
• Energy needed to keep the entropy of the
cell low
• Importance of ATP
• Autotrophs and heterotrophs-similarities
and differences
What can you tell about cell
respiration from the equation?
• Balanced Equation for Aerobic Cellular
Respiration
• C6H12O6 + (6)O2 (6)CO2 + (6)H2O + energy
• Energy (delta G=(-)140 Kcal/mol)=ATP + heat
2 ways to store energy from
exergonic breakdown of glucose
• Reduction of NAD+
• Phosphorylation of ADP
Oxidation/reduction reactions
• Definition of oxidation and reduction
• Electron and hydrogen transfer
• Reduced substances have a higher free
energy than their oxidized counterparts
LE 9-UN161
becomes oxidized
becomes reduced
LE 9-UN162a
becomes oxidized
becomes reduced
Coenzymes
• The importance of the coenzymes NAD
and FAD in cellular respiration
• Coenzymes can alternate between the
oxidized and reduced form (recycling)
• Coenzymes are present in the cell in
limited amounts
• Many enzymes (dehydrogenases) in cell
respiration require the oxidized coenzyme
(without it, they won’t work)
LE 9-4
2 e– + 2 H+
NAD+
2 e– + H+
H+
NADH
Dehydrogenase
+ 2[H]
(from food)
Nicotinamide
(oxidized form)
+
Nicotinamide
(reduced form)
H+
LE 9-UN162b
Dehydrogenase
ATP synthesis during Cellular
Respiration
• Substrate level-phosphorylation
• Oxidative phosphorylation
Substrate-level phosphorylation
• Involves the transfer of a phosphate from
one organic molecule to another during an
enzyme catalyzed reaction
• Does not require membranes to occur
• Produces a small amount of ATP/glucose
in cellular respiration (4 net ATP/glucose
out of the 38 possible produced).
LE 9-7
Enzyme
Enzyme
ADP
P
Substrate
+
Product
ATP
ATP production by Oxidative
Phsophorylation
• Use the energy of an H+ gradient to drive the
endergonic reaction of ADP + PATP
(chemiosmosis)
• The phophate transferred to ADP is inorganic
• Membranes are required (a membrane
separation two compartments)-mitochondria
• Occurs when reduced NAD and FAD are
reoxidized (recycled) during cellular respiration
• Produces most of the ATP during cell respiration
(34 ATP/glucose out of the maximum 38
possible)
Cellular Respiration is a multistep
metabolic pathway
• Why is it many individual steps rather than
1 step?
LE 9-5
H2 + 1/2 O2
+
2H
1 /2
O2
1/2
O2
(from food via NADH)
Explosive
release of
heat and light
energy
Free energy, G
Free energy, G
2 H+ + 2 e–
Controlled
release of
energy for
synthesis of
ATP
ATP
ATP
ATP
2 e–
2
H+
H2O
Uncontrolled reaction
H2O
Cellular respiration
Aerobic Cellular respiration consists of three
linked metabolic sequences
• Glycolysis
• Citric Acid (Kreb’s cycle)
• Electron Transport System
Cellular Respiration
•
•
•
•
•
•
•
•
•
•
•
•
•
Cell Biology -Respiration-Things you should know about the metabolic
sequences 1) glycolysis 2) Kreb’s cycle (including transition reaction), and
3) the electron transport system
1. Starting compound
2. end product
3. Is CO2 produced ?
4. Is NAD+ reduced?
5. Is NADH oxidized?
6. Is FAD reduced?
7. Is FADH2 oxidized?
8. Cellular location
9. Is ATP produced by substrate-level phosphorylation? If so, how much
per glucose?
10. Is ATP produced by oxidative phosphorylation? If so, how much per
glucose?
11. Is molecular oxygen (O2) directly involved in the sequence?
12. Is ATP used up during the sequence?
LE 9-6_3
Electrons carried
via NADH and
FADH2
Electrons
carried
via NADH
Glycolysis
Pyruvate
Glucose
Cytosol
Citric
acid
cycle
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
Mitochondrion
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation
LE 9-6_1
Glycolysis
Pyruvate
Glucose
Cytosol
Mitochondrion
ATP
Substrate-level
phosphorylation
LE 9-8
Energy investment phase
Glucose
2 ATP used
2 ADP + 2 P
Glycolysis
Citric
acid
cycle
Oxidative
phosphorylation
Energy payoff phase
ATP
ATP
ATP
4 ADP + 4 P
2 NAD+ + 4 e– + 4 H+
4 ATP formed
2 NADH + 2 H+
2 Pyruvate + 2 H2O
Net
Glucose
4 ATP formed – 2 ATP used
2 NAD+ + 4 e– + 4 H+
2 Pyruvate + 2 H2O
2 ATP
2 NADH + 2 H+
LE 9-9a_1
Glucose
ATP
Hexokinase
ADP
Glucose-6-phosphate
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
ATP
LE 9-9a_2
Glucose
ATP
Hexokinase
ADP
Glucose-6-phosphate
Phosphoglucoisomerase
Fructose-6-phosphate
ATP
Phosphofructokinase
ADP
Fructose1, 6-bisphosphate
Aldolase
Isomerase
Dihydroxyacetone
phosphate
Glyceraldehyde3-phosphate
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
ATP
LE 9-9b_1
2 NAD+
Triose phosphate
dehydrogenase
2 NADH
+ 2 H+
1, 3-Bisphosphoglycerate
2 ADP
Phosphoglycerokinase
2 ATP
3-Phosphoglycerate
Phosphoglyceromutase
2-Phosphoglycerate
LE 9-9b_2
2 NAD+
Triose phosphate
dehydrogenase
2 NADH
+ 2 H+
1, 3-Bisphosphoglycerate
2 ADP
Phosphoglycerokinase
2 ATP
3-Phosphoglycerate
Phosphoglyceromutase
2-Phosphoglycerate
2 H2O
Enolase
Phosphoenolpyruvate
2 ADP
Pyruvate kinase
2 ATP
Pyruvate
LE 9-18
Glucose
CYTOSOL
Pyruvate
No O2 present
Fermentation
O2 present
Cellular respiration
MITOCHONDRION
Ethanol
or
lactate
Acetyl CoA
Citric
acid
cycle
LE 9-17a
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 Ethanol
Alcohol fermentation
2 NADH
+ 2 H+
2 CO2
2 Acetaldehyde
LE 9-17b
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 CO2
2 Pyruvate
2 Lactate
Lactic acid fermentation
Summary-Fermentation
LE 9-6_3
Electrons carried
via NADH and
FADH2
Electrons
carried
via NADH
Glycolysis
Pyruvate
Glucose
Cytosol
Citric
acid
cycle
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
Mitochondrion
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation
Fermentation:
ab
o.
..
..
he
of
t
Al
l
ce
sm
or
e.
n.
..
rs
i
Pr
od
u
On
l
yo
cc
u
sa
m
e
Is
th
e
le
sr
ed
u
c..
.
as
...
20% 20% 20% 20% 20%
Re
cy
c
1. Recycles reduced
NAD back into
oxidized NAD
2. Is the same as
glycolysis
3. Only occurs in yeast
4. Produces more ATP
than glycolysis
5. All of the above
In which metabolic pathway(s)
is CO2 produced?
a) glycolysis,
b) fermentation,
c) citric acid cycle,
d) a and b,
e) b and c),
f) a and c,
g) all of the above,
h) none of the above
12%
12%
12%
12%
12%
12%
12%
at
io
itr
n,
ic
ac
id
cy
cle
,
d)
aa
nd
b,
e)
ba
nd
c),
f)
aa
g)
al
nd
lo
c,
ft
he
h)
no
ab
ne
ov
e,
of
th
e
ab
ov
e
en
t
c)
c
fe
rm
b)
a)
g
lyc
ol
ys
is,
12%
In which metabolic pathway(s) ATP produced by
substrate-level phosphorylation?
a) glycolysis,
b) fermentation,
c) citric acid cycle,
d) a and b,
e) b and c),
f) a and c,
g) all of the above,
h) none of the above
12%
12%
12%
12%
12%
12%
12%
at
io
itr
n,
ic
ac
id
cy
cle
,
d)
aa
nd
b,
e)
ba
nd
c),
f)
aa
g)
al
nd
lo
c,
ft
he
h)
no
ab
ne
ov
e,
of
th
e
ab
ov
e
en
t
c)
c
fe
rm
b)
a)
g
lyc
ol
ys
is,
12%
LE 9-11
Pyruvate
(from glycolysis,
2 molecules per glucose)
CO2
NAD+
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
Citric
acid
cycle
FADH2
2 CO2
3 NAD+
3 NADH
+ 3 H+
FAD
ADP + P i
ATP
ATP
LE 9-10
MITOCHONDRION
CYTOSOL
NAD+
NADH
+ H+
Acetyl Co A
Pyruvate
Transport protein
CO2
Coenzyme A
LE 9-12_1
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
ATP
Acetyl CoA
H2O
Oxaloacetate
Citrate
Isocitrate
Citric
acid
cycle
LE 9-12_2
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
ATP
Acetyl CoA
H2O
Oxaloacetate
Citrate
Isocitrate
CO2
Citric
acid
cycle
NAD+
NADH
+ H+
a-Ketoglutarate
NAD+
Succinyl
CoA
NADH
+ H+
CO2
LE 9-12_3
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
ATP
Acetyl CoA
H2O
Oxaloacetate
Citrate
Isocitrate
CO2
Citric
acid
cycle
NAD+
NADH
+ H+
Fumarate
a-Ketoglutarate
FADH2
NAD+
FAD
Succinate
GTP GDP
ADP
ATP
Pi
Succinyl
CoA
NADH
+ H+
CO2
LE 9-12_4
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
ATP
Acetyl CoA
NADH
+ H+
H2O
NAD+
Oxaloacetate
Malate
Citrate
Isocitrate
CO2
Citric
acid
cycle
H2O
NAD+
NADH
+ H+
Fumarate
a-Ketoglutarate
FADH2
NAD+
FAD
Succinate
GTP GDP
ADP
ATP
Pi
Succinyl
CoA
NADH
+ H+
CO2
Summary-Citric Acid cycle
Why is the citric acid cycle
important?
25%
It
g
en
er
a
te
s
O.
..
25%
ec
yc
le
so
x.
..
. ..
25%
uc
es
a
ro
d
It
p
It
c
om
pl
et
es
t..
.
25%
It
r
1. It completes the
oxidation of pyruvate
2. It produces a lot of ATP
by chemiomosis
3. It recycles oxidized NAD
back into reduced NAD
4. It generates O2 that is
needed by the ETS
If a cell is deprived of oxygen:
1. ATP production by
oxidative
phosphorylation will
cease
2. FADH2 will not be
recycled
3. The citric acid cycle will
stop
4. 1 and 2
5. All of the above
ab
o.
..
2
nd
Al
l
of
t
he
1a
i. .
.
Th
e
cit
r ic
ac
no
t
wi
ll
FA
DH
2
AT
P
pr
od
uc
t
io
n.
..
...
20% 20% 20% 20% 20%
Which of the following is not true about the
electron transport system?
20%
o.
..
o.
..
ts
c
of
i
e
So
m
as
el
ec
tr
in
It
h
sf
ou
nd
It
i
sc
ain
on
t
20% 20%
...
20%
y..
.
f..
.
5.
It
c
4.
20%
on
sis
ts
o
2.
3.
It consists of two types of
molecules, some hydrogen
and some electron carriers
It contains cytochromes
It is found in the mitochondrial
matrix
It has electron transport
system components that are
assymetrically distributed
within the mitochondrial inner
membrane
Some of its components are
iron containing proteins
It
c
1.
20%
20%
20%
16
20%
12
20%
4
1
4
8
12
16
1
1.
2.
3.
4.
5.
8
If 4 molecules of NADH are recycled by the ETS,
how many ATP could be produced at the same
time?
The mitochondrial inner
membrane:
Al
l
ab
o.
..
of
t
he
lo
ca
tio
...
Is
th
e
ch
a
in
sa
Co
nt
a
es
th
e
ra
t
20% 20%
...
20% 20%
...
im
...
Se
pa
5.
ly
4.
al
3.
20%
m
2.
Is normally impermeable to
H+
Separates the inner
membrane space and the
matrix in the mitochondria
Contains a channel protein
which is also an ATPase
enzyme
Is the location of the electron
transport system
All of the above
Is
no
r
1.
LE 9-13
NADH
50
Free energy (G) relative to O2 (kcal/mol)
FADH2
40
FMN
I
Multiprotein
complexes
FAD
Fe•S II
Fe•S
Q
III
Cyt b
30
Fe•S
Cyt c1
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidative
phosphorylation:
electron transport
and chemiosmosis
IV
Cyt c
Cyt a
Cyt a3
20
10
0
2 H+ + 1/2 O2
H2O
ATP
LE 9-15
Inner
mitochondrial
membrane
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidative
phosphorylation:
electron transport
and chemiosmosis
ATP
H+
H+
H+
H+
Intermembrane
space
Cyt c
Protein complex
of electron
carriers
Q
IV
III
I
ATP
synthase
II
Inner
mitochondrial
membrane
FADH2
NADH + H+
2H+ + 1/2 O2
H2O
FAD
NAD+
Mitochondrial
matrix
ATP
ADP + P i
(carrying electrons
from food)
H+
Electron transport chain
Electron transport and pumping of protons (H+),
Which create an H+ gradient across the membrane
Oxidative phosphorylation
Chemiosmosis
ATP synthesis powered by the flow
of H+ back across the membrane
LE 9-14
INTERMEMBRANE SPACE
H+
H+
H+
H+
H+
H+
A rotor within the
membrane spins
as shown when
H+ flows past
it down the H+
gradient.
H+
A stator anchored
in the membrane
holds the knob
stationary.
A rod (or “stalk”)
extending into
the knob also
spins, activating
catalytic sites in
the knob.
H+
ADP
+
P
ATP
i
MITOCHONDRAL MATRIX
Three catalytic
sites in the
stationary knob
join inorganic
phosphate to
ADP to make
ATP.
Summary-Electron Transport
Sytem
LE 9-16
Electron shuttles
span membrane
CYTOSOL
2 NADH
Glycolysis
Glucose
2
Pyruvate
MITOCHONDRION
2 NADH
or
2 FADH2
2 NADH
2
Acetyl
CoA
6 NADH
Citric
acid
cycle
+ 2 ATP
+ 2 ATP
by substrate-level
phosphorylation
by substrate-level
phosphorylation
Maximum per glucose:
About
36 or 38 ATP
2 FADH2
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
+ about 32 or 34 ATP
by oxidation phosphorylation, depending
on which shuttle transports electrons
form NADH in cytosol
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cytoplasm
glucose
2
net
ATP
glycolysis
2
NADH + H+
2
NADH + H+
6
NADH + H+
2
FADH2
4 or 6
ATP
6
ATP
18
ATP
4
ATP
subtotal
32
or 34
ATP
Mitochondrion
2 acetyl CoA
2 CO2
2
ATP
Citric acid
cycle
Electron transport chain
2 pyruvate
4 CO2
6 O2
subtotal
4
ATP
36 or 38
total
ATP
6 H2O
Summary-Energy Yield-Aerobic
Cellular Respiration
LE 9-19
Proteins
Carbohydrates
Amino
acids
Sugars
Glycerol Fatty
acids
Glycolysis
Glucose
Glyceraldehyde-3- P
NH3
Fats
Pyruvate
Acetyl CoA
Citric
acid
cycle
Oxidative
phosphorylation
LE 9-20
Glucose
AMP
Glycolysis
Fructose-6-phosphate
–
Stimulates
+
Phosphofructokinase
–
Fructose-1,6-bisphosphate
Inhibits
Inhibits
Pyruvate
ATP
Citrate
Acetyl CoA
Citric
acid
cycle
Oxidative
phosphorylation
Overall Summary-Cell Respiration