Lecture 7:
Cellular Respiration
Key Themes
(2) “Think Like a Biologist”: Understand What Life Is.
“Unity” of life: What are common features of eukaryotes?
Energy conversions:
Sugar breakdown & mitochondrial ATP formation
1
Yesterday’s Exit Ticket
– Energy-releasing reactions:
•
•
•
•
Large, complex  smaller, simpler
Release energy and increase entropy
e.g. ATP  ADP and Pi
e.g. respiration (glucose + O2  H2O + CO2 + ATP)
– Energy-requiring reactions:
•
•
•
•
Smaller, simpler  large complex
Decrease entropy
e.g. ADP + Pi  ATP
e.g. photosynthesis (light E + H2O + CO2  glucose + O2)
Fig. 9.1
Respiration
Food-to-Energy
Fig. 8.3
3
Cellular respiration breaks down energy-rich
molecules to CO2 & water, extracting their energy.
Light
energy
ECOSYSTEM
Low
energy
Photosynthesis
in chloroplasts
CO2 + H2O
Cellular respiration
in mitochondria
Organic+ O
molecules 2
High
energy
C-H bond
ATP
“burned” with O2
to H2O + CO2
ATP powers most cellular work
Heat
energy
4
Fig. 9.2
Since ATP is too unstable,
C-H bonds in sugars are used for energy storage.
Photosynthesis:
Light (energy)
H + & eATP
CO2 + H20
ATP
Respiration:
Converts solar energy
to ATP and uses ATP to
make sugars
Sugar [CH2O]x + O2
H + & e-
Converts the energy of sugars back to ATP
as needed.
5
What is the goal of cellular respiration?
• Food  ATP
• Release the energy in C-H bonds
• Harness that energy to create ATP
Glucose + O2
(6-C sugar)
ATP +
(energy)
CO2 + H20
O2
6-C sugar
3-C sugars
+ some ATP
CO2
+ some ATP
H + & e-
H2O + ATP
6
H+ &
e-
paraibaparadise.com
What is the goal of cellular respiration?
Step 3:
Oxidative
Phosphorylation
Step 2:
Citric Acid
Cycle
Step 1:
Glycolysis
6-C sugar
3-C sugars
+ some ATP
O2
CO2
+ some ATP
H+ & e-
H2O + ATP
7
H+ &
e-
Glucose
(6-C sugar)
Pyruvates
(3-C sugars)
+ some ATP
H+ & e-
Step 1: Glycolysis
•Occurs in: cytosol
•Starts with: glucose, NAD+, ADP, Pi
•Produces: pyruvate, NADH, and ATP
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Step 1: Glycolysis
•Occurs in: cytosol
•Starts with: glucose, NAD+, ADP, Pi
•Produces: pyruvate, NADH, and ATP
Electrons
carried off
by NADH
Fig. 9.6
Glycolysis
Glucose
Pyruvate
Cytosol
Some
ATP
9
Glucose
(6-C sugar)
Pyruvates
(3-C sugars)
+ some ATP
H+ & e-
NADH
NAD+
Step 1: Glycolysis
•Occurs in: cytosol
•Starts with: glucose, NAD+, ADP, Pi
•Produces: pyruvate, NADH, and ATP
Glycolysis can occur
with or without O10
2!!
Pyruvates
(3-C sugars)
+ some ATP
CO2
+ some ATP
H+ & e-
Step 2: Citric Acid Cycle
•Occurs in: mitochondrial matrix (fluid space)
•Starts with: pyruvate, NAD+, FAD, ADP, Pi
•Produces: NADH, FADH2, CO2 and ATP
11
Step 2: Citric Acid Cycle
•Occurs in: mitochondrial matrix (fluid space)
•Starts with: pyruvate, NAD+, FAD, ADP, Pi
•Produces: NADH, FADH2, CO2 and ATP
Fig. 9.6
Electrons
carried off
by NADH
Electrons
carried off by
NADH & FADH2
Glycolysis
Glucose
Citric
acid
cycle
Pyruvate
Mitochondrion
Cytosol
Some
ATP
Some
ATP
12
Pyruvates
(3-C sugars)
+ some ATP
CO2
+ some ATP
H+ & e-
NADH
FADH2
NAD+
FAD
Step 2: Citric Acid Cycle
•Occurs in: mitochondrial matrix (fluid space)
•Starts with: pyruvate, NAD+, FAD, ADP, Pi
•Produces: NADH, FADH2, CO2 and ATP
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O2
NADH
FADH2
H2O + ATP
NADH
ADP
Pi
Step 3: Oxidative Phosphorylation
(Using oxygen to phosphorylate ADP)
•Occurs in: mitochondrial inner membranes
•Starts with: O2, NADH, FADH2, ADP, Pi
•Produces: H2O, ATP, NAD+, FAD
14
Step 3: Oxidative Phosphorylation
(Using oxygen to phosphorylate ADP)
•Occurs in: mitochondrial inner membranes
•Starts with: O2, NADH, FADH2, ADP, Pi
•Produces: H2O, ATP, NAD+, FAD
Fig. 9.6
Electrons
carried off
by NADH
Electrons
carried off by
NADH & FADH2
Glycolysis
Glucose
Citric
acid
cycle
Pyruvate
Electron
transport
and
ATP synthase
Mitochondrion
Cytosol
Some
ATP
Some
ATP
Lots of
ATP
15
H (electrons and H+) removed from
high energy C-H bonds
O2
Glucose
(6-C sugar)
Pyruvates
(3-C sugars)
+ some ATP
CO2
+ some ATP
H+ & e(via NADH & FADH2)
H+ & e(via NADH)
H2O + ATP
16
H (electrons and H+) removed from
high energy C-H bonds
(all the way to CO2 in the citric acid cycle)
I
H - C - OH
I
(CHOH)6 (= C6H12O6 sugar)
to
O=C=O
CO2
Where does H go?
H (electrons and H+) are loaded onto
electron carriers NADH & FADH2
17
H (electrons and H+) removed from
high energy C-H bonds
O2
Glucose
(6-C sugar)
Pyruvates
(3-C sugars)
+ some ATP
CO2
+ some ATP
H+ & e(via NADH & FADH2)
H+ & e(via NADH)
H2O + ATP
18
Most ATP is formed by electron transport chain
through oxidative phosphorylation
Fig. 9.6
Electrons
carried off
by NADH
Electrons
carried off by
NADH & FADH2
Glycolysis
Glucose
Citric
acid
cycle
Pyruvate
Electron
transport
and
ATP synthase
Mitochondrion
Cytosol
2
ATP
2
ATP
~34
ATP
19
Mitochondria
Fig. 6.17
Smooth outer membrane
Matrix:
Citric acid cycle
Folded inner membrane:
20
Electron transport chain & ATP formation
Potential energy (ion gradient)
used for ATP formation
Fig. 10.16
Fig.8.7
21
Step 3: Oxidative Phosphorylation
The electron transport chain pumps protons against the
concentration gradient; builds up a high H+ concentration in
intermembrane space.
Intermembrane
space
H+
H+
Fig. 9.16
H+
Protein complex
of electron
carriers
H+
Cyt c
Q

V


FADH2 FAD
NAD+
NADH
(carrying electrons
from food)
2 H+ + 1/2O2
1 Electron transport chain
& pumping of protons
Mitochondrial matrix
Inner
membrane
ATP
synthase
H2O
ADP + Pi
ATP
H+
2
ATP synthesis via H+ flow
22
Mitochondria
Fig. 6.17
Smooth outer membrane
Matrix
Intermembrane
space
Folded inner membrane
23
Step 3: Oxidative Phosphorylation
Protons flow downhill through the ATP synthase, driving
phosphorylation of ADP to ATP.
Fig. 9.14
Oxygen (O2) is the final electron (and
Intermembrane
space
H+)
H+
H+
acceptor
INTERMEMBRANE SPACE
H+
Fig. 9.16
Stator
Rotor
H+
Protein complex
of electron
carriers
H+
Cyt c
Q

V


FADH2 FAD
NAD+
NADH
(carrying electrons
from food)
2 H+ + 1/2O2
1 Electron transport chain
& pumping of protons
Mitochondrial matrix
Inner
membrane
Internal
ATP
rod
synthase
H2O
ADP + Pi
ATP
H+
2
ATP synthesis via H+ flow
Catalytic
knob
ADP
+
P
ATP
24
i
MITOCHONDRIAL MATRIX
Let’s take a look at the whole sequence:
• Step 1: Glycolysis
• Step 2: Citric Acid Cycle
• Step 3: Oxidative Phosphorylation
http://www.colorado.edu/ebio/genbio/09_15ElectronTransport_A.html
25
Electron Donors and Electron Acceptors
Electron acceptor
from mitochondrial
electron
transport chain
O2
Glucose
(6-C sugar)
Pyruvates
(3-C sugars)
+ some ATP
CO2
+ some ATP
H+ & e(via NADH & FADH2)
H+ & e(via NADH)
H2O + ATP
Electron donors
Original electron donor
in cellular respiration
for mitochondrial
electron transport
chain
26
ATP links the energy from breakdown of
energy-rich food molecules to cellular work
Energy loaded onto
ATP
Energy from
breakdown of
energy-rich
molecules
ATP + H2O
Fig. 8.12
Energy released from
ATP
Energy for cellular
work
ADP + P i
27
The cellular respiration
pathway for
Proteins
Carbohydrates
Amino
acids
Sugars
Fats
Glycerol
Fatty
acids
Glycolysis
Glucose
Glyceraldehyde-3- P
Carbohydrates
NH3
Pyruvate
Fats
Acetyl CoA
Proteins
Citric
acid
cycle
Fig. 9.20
Oxidative
phosphorylation
28
Predict how the enzymes that function early in glycolysis,
and start the breakdown of glucose, should be regulated:
The enzymes should
A) not be regulated.
B) be turned off when enough (ATP) energy is available.
C) be turned on when more (ATP) energy is needed.
D) be regulated in a dual way, both by activation when
more ATP energy is needed and by inactivation when
enough ATP energy is available.
29
5 min break
30
www.stthomasblog.com
Key Themes
Energy conversions:
Sugar breakdown without oxygen
via glycolysis + fermentation
31
• Step 1 of cellular respiration:
Glucose
Glycolysis
Pyruvate
Glycolysis
outside
mitochondria
From glucose
(6 C) to 2
pyruvate (3 C)
CYTOSOL
MITOCHONDRION
Citric
acid
cycle
Fig. 9.19
32
Glucose
•Only when
oxygen is
present
can glucose
be broken
down
completely
in the
mitochondria
for high energy
yield
Glycolysis
CYTOSOL
Pyruvate
O2 present:
Aerobic cellular
respiration
MITOCHONDRION
Acetyl CoA
Citric
acid
cycle
Fig. 9.19
33
Glucose
Glycolysis
CYTOSOL
Pyruvate
No O2
present:
Fermentation
MITOCHONDRION
Ethanol
or
lactate
Fig. 9.19
Acetyl CoA
Citric
acid
cycle
34
2 ADP + 2 P i
The solution when oxygen runs out or
is unavailable (anaerobic conditions): Glucose
2 ATP
Glycolysis
Glycolysis & fermentation
Alcoholic fermentation
(forms ethanol plus CO2)
by yeasts and bacteria
under anaerobic conditions
2 Pyruvate
2 NAD+
2 Ethanol
2 NADH
+ 2 H+
2 CO2
(a) Alcohol fermentation
2 Acetaldehyde
Fig. 9.18
35
Production of Foods & Fuels
Fig. 9.18(a)
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 Ethanol
2 NADH
+ 2 H+
2 CO2
(a) Alcohol fermentation
2 Acetaldehyde
Glycolysis and fermentation
Fermentation to ethanol
Yeasts use alcoholic fermentation to convert
hexoses (from sugar cane sucrose or corn starch or
36
cellulose) into ethanol for fuels
2 ADP + 2 P i
Glycolysis & fermentation
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
Alcohol fermentation
(forms ethanol plus CO2)
• Yeasts & bacteria
• Anaerobic conditions
2 Ethanol
2 NADH
+ 2 H+
2 CO2
(a) Alcohol fermentation
2 Acetaldehyde
Fig. 9.18
Do all organisms use alcohol
fermentation when oxygen is in
short supply?
37
2 ADP + 2 P i
Glycolysis & fermentation
without oxygen (anaerobic
conditions)
Alcohol fermentation
(forms ethanol plus CO2)
• Yeasts & bacteria
• Anaerobic conditions
Fig. 9.18
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 NADH
+ 2 H+
2 CO2
(a) Alcohol fermentation
2 Acetaldehyde
2 Ethanol
2 ADP + 2 P
Glucose
Lactic acid fermentation
• Other fungi & bacteria
• Also in muscle cells under
anaerobic conditions
2 ATP
i
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 Pyruvate
(b) Lactic acid fermentation
2 Lactate
38
Production of Foods and
Fuels by Microbes in
home & industry
Yeasts for beer & wine
[alcohol fermentation] &
for bread leavening [from
the CO2 gas formed];
lactic acid bacteria for
fermented products from
milk or other foods
[lactic acid fermentation].
39
http://www.bact.wisc.edu/themicrobialworld/Effects.html
Different human muscle fibers use
different metabolism (See also Table 49.1):
Fermentation versus aerobic respiration
Glucose
CYTOSOL
Glycolysis
Pyruvate
Fermentation
Aerobic cellular
respiration
MITOCHONDRION
Lactate
Acetyl CoA
Citric
acid
cycle
40
Fig. 9.19
Different human muscle fibers use
different metabolism (See also Table 49.1):
Fermentation versus aerobic respiration
Glycogen
CYTOSOL
Glucose
Glycolysis
Pyruvate
Fermentation
Aerobic cellular
respiration
• Fast-twitch glycolytic
fibers (for sprint) use
glycolysis - quick, but
does not provide much
energy.
MITOCHONDRION
Lactate
Acetyl CoA
Citric
acid
cycle
41
Fig. 9.19
Different human muscle fibers use
different metabolism (See also Table 49.1):
Fermentation versus aerobic respiration
[Glucose]
CYTOSOL
Fats
Glycolysis
Pyruvate
Fermentation
Aerobic cellular
respiration
MITOCHONDRION
Lactate
Acetyl CoA
Citric
acid
cycle
Fig. 9.19
• Fast-twitch glycolytic
fibers (for sprint) use
glycolysis - quick, but
does not provide much
energy.
• Slow-twitch oxidative
fibers (with many
mitochondria for
extended exercise) use
oxidative respiration slower, but yields much
42
more energy.
Glucose
Glycolysis
Fermentation
in absence
of O2
Aerobic
respiration in
presence
of O2
CYTOSOL
Pyruvate
No O2
present:
Fermentation
O2 present:
Aerobic cellular
respiration
MITOCHONDRION
Ethanol
or
lactate
Fig. 9.19
Acetyl CoA
Citric
acid
cycle
43
Fig. 9.5
44
Hank’s Crash Course
in Cellular Respiration
3:30-end
http://www.youtube.com/watch?v=00jbG_cf
GuQ&feature=relmfu
45
Today’s Exit Ticket
Process:
Process:
Process:
Glucose
Location:
Location:
Products Released:
# ATPs:
# ATPs:
Location:
Products Released:
# ATPs:
46