BIOL 101 Chp 9: Cellular Respiration and Fermentation
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Transcript of BIOL 101 Chp 9: Cellular Respiration and Fermentation
Cellular Respiration
BIOL 101: General Biology I
Chapter 9
Rob Swatski Associate Professor of Biology
HACC – York Campus
Energy & Open
Systems Energy enters an
ecosystem as sunlight…
…and exits as heat
Photosynthesis O2 + Glucose
Cellular Respiration CO2 + ATP + heat
2
Light energy
ECOSYSTEM
Photosynthesis in chloroplasts
CO2 + H2O
Cellular respiration in mitochondria
Organic molecules
+ O2
ATP powers most cellular work
Heat energy
ATP
exergonic
endergonic
3
4
Catabolic Pathways
Anaerobic respiration (fermentation)
Partial breakdown of organics that
occurs without O2 Yields 2 ATP
Aerobic respiration
Complete breakdown of
organics with O2
Yields 36 or 38 ATP
5
C6H12O6 + 6 O2 6 CO2 + 6 H2O + Energy
6
Reduction
Oxidation
Redox Reactions
e-
is oxidized (loses e-)
becomes reduced (gains e-)
General Example of a Redox Reaction
7
is oxidized
becomes reduced
Aerobic Cellular Respiration = Redox Reaction
8
9
Electron Transfer in
Cellular Respiration
Uses the coenzyme: NAD+
NAD+ (oxidized) is both an electron
acceptor & oxidizing agent
NADH (reduced) represents stored
energy used to synthesize ATP
Dehydrogenase
e-
10
e- e-
11
Dehydrogenase
Reduction of NAD+
Oxidation of NADH
2 e– + 2 H+ 2 e– + H+
NAD+ + 2[H]
NADH
+
H+
H+
Nicotinamide (oxidized)
Nicotinamide (reduced)
12
13
Where do all the electrons
go?
Electron Transport Chain (ETC)
ETC passes e- in a series of steps
O2 pulls e- down the ETC in an
energy-yielding tumble
This energy is used to make ATP
Uncontrolled reaction
H2 + 1/2 O2
Explosive release of
heat and light energy
Cellular respiration
Controlled release of energy for
synthesis of ATP
2 H+ + 2 e–
2 H 1/2 O2
(from food via NADH)
1/2 O2
14
15
Cellular Respiration: 3 Main Stages
Glycolysis
Citric Acid Cycle (Krebs Cycle)
Oxidative phosphorylation
Substrate-level phosphorylation
ATP
Cytosol
Glucose Pyruvate
Glycolysis
Electrons carried
via NADH
16
Mitochondrion
Substrate-level phosphorylation
ATP
Cytosol
Glucose Pyruvate
Glycolysis
Electrons carried
via NADH
Substrate-level phosphorylation
ATP
Electrons carried via NADH and
FADH2
Citric acid cycle
17
Mitochondrion
Substrate-level phosphorylation
ATP
Cytosol
Glucose Pyruvate
Glycolysis
Electrons carried
via NADH
Substrate-level phosphorylation
ATP
Electrons carried via NADH and
FADH2
Oxidative phosphorylation
ATP
Citric acid cycle
Oxidative phosphorylation:
e- transport &
chemiosmosis
18
Enzyme
ADP
P
Substrate
Enzyme
ATP +
Product
Substrate-Level Phosphorylation
Used to make smaller amounts
of ATP
Uses glycolysis & citric acid cycle
19
20
Glycolysis
Occurs in cytoplasm
Glucose pyruvate
2 Major Phases
21
2 Major Phases of Glycolysis
1. Energy investment
phase
2. Energy payoff phase
Energy Investment Phase
Glucose
2 ADP + 2 P 2 ATP used
formed 4 ATP
Energy Payoff Phase
4 ADP + 4 P
2 NAD+ + 4 e– + 4 H+ 2 NADH + 2 H+
2 Pyruvate + 2 H2O
2 Pyruvate + 2 H2O Glucose Net
4 ATP formed – 2 ATP used 2 ATP
2 NAD+ + 4 e– + 4 H+ 2 NADH + 2 H+
22
ATP
ADP
Hexokinase
1
ATP
ADP
Hexokinase
1
Glucose
Glucose-6-phosphate
Glucose
Glucose-6-phosphate
Energy Investment Phase 23
Hexokinase
ATP
ADP
1
Phosphoglucoisomerase
2
Phosphogluco- isomerase
2
Glucose
Glucose-6-phosphate
Fructose-6-phosphate
Glucose-6-phosphate
Fructose-6-phosphate
isomer
24
1
Hexokinase
ATP
ADP
Phosphoglucoisomerase
Phosphofructokinase
ATP
ADP
2
3
ATP
ADP
Phosphofructo- kinase
Fructose- 1, 6-bisphosphate
Glucose
Glucose-6-phosphate
Fructose-6-phosphate
Fructose- 1, 6-bisphosphate
1
2
3
Fructose-6-phosphate
3
Energy Investment Phase 25
Glucose
ATP
ADP
Hexokinase
Glucose-6-phosphate
Phosphoglucoisomerase
Fructose-6-phosphate
ATP
ADP
Phosphofructokinase
Fructose- 1, 6-bisphosphate
Aldolase
Isomerase
Dihydroxyacetone phosphate
Glyceraldehyde- 3-phosphate
1
2
3
4
5
Aldolase
Isomerase
Fructose- 1, 6-bisphosphate
Dihydroxyacetone phosphate
Glyceraldehyde- 3-phosphate
4
5
26
2 NAD+
NADH 2
+ 2 H+
2
2 P i
Triose phosphate dehydrogenase
1, 3-Bisphosphoglycerate
6
2 NAD+
Glyceraldehyde- 3-phosphate
Triose phosphate dehydrogenase
NADH 2
+ 2 H+
2 P i
1, 3-Bisphosphoglycerate
6
2
2
Energy Capture Phase
e-
27
2 NAD+
NADH 2
Triose phosphate dehydrogenase
+ 2 H+
2 P i
2
2 ADP
1, 3-Bisphosphoglycerate
Phosphoglycerokinase
2 ATP
2 3-Phosphoglycerate
6
7
2 2 ADP
2 ATP
1, 3-Bisphosphoglycerate
3-Phosphoglycerate
Phosphoglycero- kinase
2
7
2 ATP
28
3-Phosphoglycerate
Triose phosphate dehydrogenase
2 NAD+
2 NADH
+ 2 H+
2 P i
2
2 ADP
Phosphoglycerokinase
1, 3-Bisphosphoglycerate
2 ATP
3-Phosphoglycerate 2
Phosphoglyceromutase
2-Phosphoglycerate 2
2-Phosphoglycerate 2
2
Phosphoglycero- mutase
6
7
8
8
29
2 NAD+
NADH 2
2
2
2
2
+ 2 H+
Triose phosphate dehydrogenase
2 P i
1, 3-Bisphosphoglycerate
Phosphoglycerokinase
2 ADP
2 ATP
3-Phosphoglycerate
Phosphoglyceromutase
Enolase
2-Phosphoglycerate
2 H2O
Phosphoenolpyruvate
9
8
7
6
2 2-Phosphoglycerate
Enolase
2
2 H2O
Phosphoenolpyruvate
9
30
Triose phosphate dehydrogenase
2 NAD+
NADH 2
2
2
2
2
2
2 ADP
2 ATP
Pyruvate
Pyruvate kinase
Phosphoenolpyruvate
Enolase 2 H2O
2-Phosphoglycerate
Phosphoglyceromutase
3-Phosphoglycerate
Phosphoglycerokinase
2 ATP
2 ADP
1, 3-Bisphosphoglycerate
+ 2 H+
6
7
8
9
10
2 2 ADP
2 ATP
Phosphoenolpyruvate
Pyruvate kinase
2 Pyruvate
10
2 P i
2 ATP
31
32
Summary of Glycolysis
• Location within cell:
• Aerobic or anaerobic:
• Initial reactant:
• Final product(s):
• Side products:
• Net yield of energy:
33
Summary of Glycolysis
• Location within cell:
• Aerobic or anaerobic:
• Initial reactant:
• Final product(s):
• Side products:
• Net yield of energy:
cytosol
anaerobic
glucose
2 pyruvate molecules
2 NADH
2 ATP (4 created; 2 invested)
34
The Fate of Pyruvate
When O2 is present, pyruvate
enters mitochondrion
Pyruvate must be converted to acetyl CoA
Transition reaction: b/w glycolysis &
citric acid cycle
CYTOSOL MITOCHONDRION
NAD+ NADH + H+
2
1 3
Pyruvate
Transport protein
CO2 Coenzyme A
Acetyl CoA
e-
Transition Between Glycolysis & the Citric Acid Cycle
35
Pyruvate
NAD+
NADH
+ H+ Acetyl CoA
CO2
CoA
CoA
CoA
Citric acid cycle
FADH2
FAD
CO2 2
3
3 NAD+
+ 3 H+
ADP + P i
ATP
NADH
36
37
Citric Acid Cycle (Krebs Cycle)
8 steps: each catalyzed by a
specific enzyme
Acetyl group (of acetyl CoA)
combines with oxaloacetate to
form citrate
The next 7 steps decompose citrate
back into oxaloacetate
NADH & FADH2 relay e- to the ETC
Acetyl CoA
Oxaloacetate
CoA—SH
1
Citrate
Citric acid cycle
38
Acetyl CoA
Oxaloacetate
Citrate
CoA—SH
Citric acid cycle
1
2
H2O
Isocitrate
39
Acetyl CoA
CoA—SH
Oxaloacetate
Citrate
H2O
Citric acid cycle
Isocitrate
1
2
3
NAD+
NADH
+ H+
-Keto- glutarate
CO2
e-
40
Acetyl CoA
CoA—SH
Oxaloacetate
Citrate
H2O
Isocitrate NAD+
NADH
+ H+ Citric acid cycle
-Keto- glutarate
CoA—SH
1
2
3
4
NAD+
NADH
+ H+ Succinyl CoA
CO2
CO2
e-
41
Acetyl CoA
CoA—SH
Oxaloacetate
Citrate
H2O
Isocitrate NAD+
NADH
+ H+
CO2
Citric acid cycle
CoA—SH
-Keto- glutarate
CO2 NAD+
NADH
+ H+ Succinyl CoA
1
2
3
4
5
CoA—SH
GTP GDP
ADP
P i Succinate
ATP ATP
42
Acetyl CoA
CoA—SH
Oxaloacetate
H2O
Citrate Isocitrate
NAD+
NADH
+ H+
CO2
Citric acid cycle
CoA—SH
-Keto- glutarate
CO2 NAD+
NADH
+ H+
CoA—SH
P
Succinyl CoA
i
GTP GDP
ADP
ATP
Succinate
FAD
FADH2
Fumarate
1
2
3
4
5
6
FAD e-
Flava Flav
43
Acetyl CoA
CoA—SH
Oxaloacetate
Citrate
H2O
Isocitrate NAD+
NADH
+ H+
CO2
-Keto- glutarate
CoA—SH
NAD+
NADH
Succinyl CoA
CoA—SH
P P
GDP GTP
ADP
ATP
Succinate
FAD
FADH2
Fumarate
Citric acid cycle
H2O
Malate
1
2
5
6
7
i
CO2
+ H+
3
4
44
Acetyl CoA
CoA—SH
Citrate
H2O
Isocitrate NAD+
NADH
+ H+
CO2
-Keto- glutarate
CoA—SH
CO2 NAD+
NADH
+ H+ Succinyl CoA
CoA—SH
P i
GTP GDP
ADP
ATP
Succinate
FAD
FADH2
Fumarate
Citric acid cycle
H2O
Malate
Oxaloacetate
NADH
+H+
NAD+
1
2
3
4
5
6
7
8
e-
45
Inputs Outputs
Acetyl CoA 2
2
2
2
6
ATP
NADH
FADH2
Oxaloacetate
Citric acid cycle
S—CoA
CH3
C O
O C COO
CH2
COO
46
47
Summary of Citric Acid (Krebs) Cycle
• Location within cell:
• Aerobic or anaerobic:
• Initial reactant:
• Final product(s):
• Side products:
• Net yield of energy:
48
• Location within cell:
• Aerobic or anaerobic:
• Initial reactant:
• Final product(s):
• Side products:
• Net yield of energy:
mitochondrion
aerobic
citric acid
oxaloacetate
NADH & FADH2 (10 e- total) 6 CO2
2 ATP (1 per turn)
Summary of Citric Acid (Krebs) Cycle
49
Electron Transport Chain
(ETC)
ETC is in cristae of mitochondria
Consists of multiprotein complexes
(cytochromes)
Proteins alternate b/w reduced & oxidized states
Electrons drop in free energy as
they travel down ETC
50
ETC and Energy
ETC does not directly generate
ATP
It divides the free energy drop into
smaller steps
Energy is released in manageable
amounts
Electrons are finally passed to O2, forming H2O
NADH
NAD+ 2
FADH2
2 FAD
Multiprotein complexes FAD
Fe•S
FMN
Fe•S
Q
Fe•S
Cyt b
Cyt c1
Cyt c
Cyt a
Cyt a3
IV
50
40
30
20
10 2
(from NADH or FADH2)
0 2 H+ + 1/2 O2
H2O
e–
e–
e–
51
NADH
NAD+ 2
FADH2
2 FAD
Multiprotein complexes FAD
Fe•S
FMN
Fe•S
Q
Fe•S
Cyt b
Cyt c1
Cyt c
Cyt a
Cyt a3
IV
50
40
30
20
10 2
(from NADH or FADH2)
0 2 H+ + 1/2 O2
H2O
e–
e–
e–
e- e-
FADH2 e- e- FAD
52
53
Chemiosmosis
Uses energy from H+ gradient to drive
cellular work
Proteins pump H+ from mitochondrial
matrix to intermembrane space
H+ then moves back across membrane,
passing through ATP synthase
Exergonic flow of H+ drives ATP
phosphorylation
Protein complex of electron carriers
H+
H+ H+
Cyt c
Q
V
FADH2 FAD
NAD+ NADH
(carrying electrons from food)
Electron transport chain
2 H+ + 1/2O2 H2O
ADP + P i
Chemiosmosis
Oxidative phosphorylation
H+
H+
ATP synthase
ATP
2 1
H+ H+
H+ H+
54
Protein complex of electron carriers
H+
H+ H+
Cyt c
Q
V
FADH2 FAD
NAD+ NADH
(carrying electrons from food)
Electron transport chain
2 H+ + 1/2O2 H2O
ADP + P i
Chemiosmosis
Oxidative phosphorylation
H+
H+
ATP synthase
ATP
2 1
ATP
H+ H+
H+ H+
H+
H+
H+
H+
H+
H+
H+ H+
H+ H+ H+
H+
H+
55
56
INTER- MEMBRANE SPACE
H+
ATP synthase
ATP ADP + P i
H+ MITO- CHONDRIAL MATRIX
Proton-Motive
Force
ATP
H+
57
58
Summary of Electron Transport Chain
• Location within cell:
• Aerobic or anaerobic:
• Side products:
• Final electron acceptor:
• Final product:
• Net yield of energy:
59
• Location within cell:
• Aerobic or anaerobic:
• Side products:
• Final electron acceptor:
• Final product:
• Net yield of energy:
mitochondrion
aerobic
12 NADH and FADH2
O2
H2O
32 ATP
Summary of Electron Transport Chain
Glucose
NADH
ETC
Proton-motive force
ATP
60
The Flow of Energy in Cellular Respiration
Maximum ATP per glucose:
About 36 or 38 ATP
+ 2 ATP + 2 ATP + about 32 or 34 ATP
Oxidative phosphorylation: electron transport & chemiosmosis
Citric acid cycle
2 Acetyl
CoA
Glycolysis
Glucose 2
Pyruvate
2 NADH 2 NADH 6 NADH 2 FADH2
2 FADH2
2 NADH
CYTOSOL
Electron shuttles span membrane
or
MITOCHONDRION
36 or 38 ATP
61
62
Fermentation (Anaerobic
Respiration) Glycolysis can produce ATP
with or without O2
Couples with fermentation
Alcohol fermentation
Lactic acid fermentation
63
Alcohol Fermentation
Pyruvate Ethanol
CO2 released
Yeast: brewing & baking
2 ADP + 2 P i 2 ATP
Glucose Glycolysis
2 Pyruvate
2 NADH 2 NAD+
+ 2 H+ CO2
2 Acetaldehyde 2 Ethanol
Alcohol Fermentation
2
2 ATP
64
65
Lactic Acid Fermentation
Pyruvate is reduced to
NADH
Lactate is formed as end-
product
CO2 is not released
Fungi & bacteria cheese &
yogurt
66
Glucose
2 ADP + 2 P i 2 ATP
Glycolysis
2 NAD+ 2 NADH
+ 2 H+ 2 Pyruvate
2 Lactate
Lactic Acid Fermentation
2 ATP
67
68
Comparison of Aerobic Respiration
& Fermentation
Both use glycolysis (glu pyruvate)
Have different final e- acceptors (O2 vs.
pyruvate/acetaldehyde)
Aerobic respiration produces 36 or 38 ATP
per glucose
Fermentation only produces 2 ATP per
glucose
69
Obligate anaerobes
Use fermentation or anaerobic respiration
Cannot survive in presence of O2
Facultative anaerobes
Use either fermentation or
aerobic respiration
Yeast & many bacteria
Opisthotonus. (Tetanus), c.1809 Charles Bell (1774-1842)
Clostridium tetani -obligate anaerobe
70
71
The Evolutionary Significance of Glycolysis Glycolysis occurs in nearly all organisms
- most likely evolved in ancient prokaryotes before there was O2 in the atmosphere
Glucose
Glycolysis
Pyruvate CYTOSOL
No O2 present:
Fermentation
O2 present:
Aerobic cellular
respiration
MITOCHONDRION
Acetyl CoA Ethanol or
lactate Citric acid cycle
Pyruvate is a “fork in the metabolic road”
72