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LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserma...
Overview: Life Is Work
• Living cells require energy from outside
sources
• Some animals, such as the chimpanzee, obtain
e...
Figure 9.1
• Energy flows into an ecosystem as sunlight
and leaves as heat
• Photosynthesis generates O2 and organic
molecules, which...
Figure 9.2
Light
energy
ECOSYSTEM
Photosynthesis
in chloroplasts
Cellular respiration
in mitochondria
CO2 + H2O + O2
Organ...
Concept 9.1: Catabolic pathways yield
energy by oxidizing organic fuels
• Several processes are central to cellular
respir...
Catabolic Pathways and Production of ATP
• The breakdown of organic molecules is
exergonic
• Fermentation is a partial deg...
• Cellular respiration includes both aerobic and
anaerobic respiration but is often used to refer to
aerobic respiration
•...
Redox Reactions: Oxidation and Reduction
• The transfer of electrons during chemical
reactions releases energy stored in o...
The Principle of Redox
• Chemical reactions that transfer electrons
between reactants are called oxidation-reduction
react...
Figure 9.UN01
becomes oxidized
(loses electron)
becomes reduced
(gains electron)
Figure 9.UN02
becomes oxidized
becomes reduced
• The electron donor is called the reducing
agent
• The electron receptor is called the oxidizing
agent
• Some redox react...
Figure 9.3
Reactants Products
Energy
WaterCarbon dioxideMethane
(reducing
agent)
Oxygen
(oxidizing
agent)
becomes oxidized...
Oxidation of Organic Fuel Molecules During
Cellular Respiration
• During cellular respiration, the fuel (such as
glucose) ...
Figure 9.UN03
becomes oxidized
becomes reduced
Stepwise Energy Harvest via NAD+
and the
Electron Transport Chain
• In cellular respiration, glucose and other organic
mol...
Figure 9.4
Nicotinamide
(oxidized form)
NAD+
(from food)
Dehydrogenase
Reduction of NAD+
Oxidation of NADH
Nicotinamide
(r...
Figure 9.UN04
Dehydrogenase
• NADH passes the electrons to the electron
transport chain
• Unlike an uncontrolled reaction, the electron
transport chai...
Figure 9.5
(a) Uncontrolled reaction (b) Cellular respiration
Explosive
release of
heat and light
energy
Controlled
releas...
The Stages of Cellular Respiration:
A Preview
• Harvesting of energy from glucose has three
stages
– Glycolysis (breaks do...
Figure 9.UN05
Glycolysis (color-coded teal throughout the chapter)1.
Pyruvate oxidation and the citric acid cycle
(color-c...
Figure 9.6-1
Electrons
carried
via NADH
Glycolysis
Glucose Pyruvate
CYTOSOL MITOCHONDRION
ATP
Substrate-level
phosphorylat...
Figure 9.6-2
Electrons
carried
via NADH
Electrons carried
via NADH and
FADH2
Citric
acid
cycle
Pyruvate
oxidation
Acetyl C...
Figure 9.6-3
Electrons
carried
via NADH
Electrons carried
via NADH and
FADH2
Citric
acid
cycle
Pyruvate
oxidation
Acetyl C...
• The process that generates most of the ATP is
called oxidative phosphorylation because it is
powered by redox reactions
...
• Oxidative phosphorylation accounts for almost
90% of the ATP generated by cellular
respiration
• A smaller amount of ATP...
Figure 9.7
Substrate
Product
ADP
P
ATP
Enzyme Enzyme
Concept 9.2: Glycolysis harvests chemical
energy by oxidizing glucose to pyruvate
• Glycolysis (“splitting of sugar”) brea...
Figure 9.8
Energy Investment Phase
Glucose
2 ADP + 2 P
4 ADP + 4 P
Energy Payoff Phase
2 NAD+
+ 4 e−
+ 4 H+
2 Pyruvate + 2...
Figure 9.9-1
Glycolysis: Energy Investment Phase
ATP
Glucose Glucose 6-phosphate
ADP
Hexokinase
1
Figure 9.9-2
Glycolysis: Energy Investment Phase
ATP
Glucose Glucose 6-phosphate Fructose 6-phosphate
ADP
Hexokinase Phosp...
Figure 9.9-3
Glycolysis: Energy Investment Phase
ATP ATP
Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bis...
Figure 9.9-4
Glycolysis: Energy Investment Phase
ATP ATP
Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bis...
Figure 9.9-5
Glycolysis: Energy Payoff Phase
2 NADH
2 NAD+ +2 H+
2 P i
1,3-Bisphospho-
glycerate6
Triose
phosphate
dehydro...
Figure 9.9-6
Glycolysis: Energy Payoff Phase
2 ATP
2 NADH
2 NAD+ +2 H+
2 P i
2 ADP
1,3-Bisphospho-
glycerate
3-Phospho-
gl...
Figure 9.9-7
Glycolysis: Energy Payoff Phase
2 ATP
2 NADH
2 NAD+ +2 H+
2 P i
2 ADP
1,3-Bisphospho-
glycerate
3-Phospho-
gl...
Figure 9.9-8
Glycolysis: Energy Payoff Phase
2 ATP
2 NADH
2 NAD+ +2 H+
2 P i
2 ADP
1,3-Bisphospho-
glycerate
3-Phospho-
gl...
Figure 9.9-9
Glycolysis: Energy Payoff Phase
2 ATP 2 ATP
2 NADH
2 NAD+ +2 H+
2 P i
2 ADP
1,3-Bisphospho-
glycerate
3-Phosp...
Figure 9.9a
Glycolysis: Energy Investment Phase
ATP
Glucose Glucose 6-phosphate
ADP
Hexokinase
1
Fructose 6-phosphate
Phos...
Figure 9.9b
Glycolysis: Energy Investment Phase
ATP
Fructose 6-phosphate
ADP
3
Fructose 1,6-bisphosphate
Phospho-
fructoki...
Figure 9.9c
Glycolysis: Energy Payoff Phase
2 NADH
2 ATP
2 ADP 2
2
2 NAD+ + 2 H+
2 P i
3-Phospho-
glycerate
1,3-Bisphospho...
Figure 9.9d
Glycolysis: Energy Payoff Phase
2 ATP
2 ADP
2222
2 H2O
PyruvatePhosphoenol-
pyruvate (PEP)
2-Phospho-
glycerat...
Concept 9.3: After pyruvate is oxidized, the
citric acid cycle completes the energy-
yielding oxidation of organic molecul...
Oxidation of Pyruvate to Acetyl CoA
• Before the citric acid cycle can begin, pyruvate
must be converted to acetyl Coenzym...
Figure 9.10
Pyruvate
Transport protein
CYTOSOL
MITOCHONDRION
CO2 Coenzyme A
NAD+ + H+
NADH Acetyl CoA
1
2
3
• The citric acid cycle, also called the Krebs
cycle, completes the break down of pyruvate
to CO2
• The cycle oxidizes org...
Figure 9.11
Pyruvate
NAD+
NADH
+ H+
Acetyl CoA
CO2
CoA
CoA
CoA
2 CO2
ADP + P i
FADH2
FAD
ATP
3 NADH
3 NAD+
Citric
acid
cyc...
• The citric acid cycle has eight steps, each
catalyzed by a specific enzyme
• The acetyl group of acetyl CoA joins the cy...
Figure 9.12-1
1
Acetyl CoA
Citrate
Citric
acid
cycle
CoA-SH
Oxaloacetate
Figure 9.12-2
1
Acetyl CoA
Citrate
Isocitrate
Citric
acid
cycle
H2O
2
CoA-SH
Oxaloacetate
Figure 9.12-3
1
Acetyl CoA
Citrate
Isocitrate
α-Ketoglutarate
Citric
acid
cycle
NADH
+ H+
NAD+
H2O
3
2
CoA-SH
CO2
Oxaloace...
Figure 9.12-4
1
Acetyl CoA
Citrate
Isocitrate
α-Ketoglutarate
Succinyl
CoA
Citric
acid
cycle
NADH
NADH
+ H+
+ H+
NAD+
NAD+...
Figure 9.12-5
1
Acetyl CoA
Citrate
Isocitrate
α-Ketoglutarate
Succinyl
CoA
Succinate
Citric
acid
cycle
NADH
NADH
ATP
+ H+
...
Figure 9.12-6
1
Acetyl CoA
Citrate
Isocitrate
α-Ketoglutarate
Succinyl
CoA
Succinate
Fumarate
Citric
acid
cycle
NADH
NADH
...
Figure 9.12-7
1
Acetyl CoA
Citrate
Isocitrate
α-Ketoglutarate
Succinyl
CoA
Succinate
Fumarate
Malate
Citric
acid
cycle
NAD...
Figure 9.12-8
NADH
1
Acetyl CoA
Citrate
Isocitrate
α-Ketoglutarate
Succinyl
CoA
Succinate
Fumarate
Malate
Citric
acid
cycl...
Figure 9.12a
Acetyl CoA
Oxaloacetate
Citrate
Isocitrate
H2O
CoA-SH
1
2
Figure 9.12b
Isocitrate
α-Ketoglutarate
Succinyl
CoA
NADH
NADH
NAD+
NAD+
+ H+
CoA-SH
CO2
CO2
3
4
+ H+
Figure 9.12c
Fumarate
FADH2
CoA-SH6
Succinate
Succinyl
CoA
FAD
ADP
GTP GDP
P i
ATP
5
Figure 9.12d
Oxaloacetate8
Malate
Fumarate
H2O
NADH
NAD+
+ H+
7
Concept 9.4: During oxidative
phosphorylation, chemiosmosis couples
electron transport to ATP synthesis
• Following glycol...
The Pathway of Electron Transport
• The electron transport chain is in the inner
membrane (cristae) of the mitochondrion
•...
Figure 9.13
NADH
FADH2
2 H+
+ 1
/2 O2
2 e−
2 e−
2 e−
H2O
NAD+
Multiprotein
complexes
(originally from
NADH or FADH2)
I
II
...
• Electrons are transferred from NADH or FADH2
to the electron transport chain
• Electrons are passed through a number of
...
Chemiosmosis: The Energy-Coupling
Mechanism
• Electron transfer in the electron transport chain
causes proteins to pump H+...
Figure 9.14
INTERMEMBRANE SPACE
Rotor
Stator
H+
Internal
rod
Catalytic
knob
ADP
+
P i ATP
MITOCHONDRIAL MATRIX
Figure 9.15
Protein
complex
of electron
carriers
(carrying electrons
from food)
Electron transport chain
Oxidative phospho...
• The energy stored in a H+
gradient across a
membrane couples the redox reactions of the
electron transport chain to ATP ...
An Accounting of ATP Production by
Cellular Respiration
• During cellular respiration, most energy flows
in this sequence:...
Figure 9.16
Electron shuttles
span membrane
MITOCHONDRION
2 NADH
2 NADH 2 NADH 6 NADH
2 FADH2
2 FADH2
or
+ 2 ATP+ 2 ATP + ...
Concept 9.5: Fermentation and anaerobic
respiration enable cells to produce ATP
without the use of oxygen
• Most cellular ...
• Anaerobic respiration uses an electron
transport chain with a final electron acceptor
other than O2, for example sulfate...
Types of Fermentation
• Fermentation consists of glycolysis plus
reactions that regenerate NAD+
, which can be
reused by g...
• In alcohol fermentation, pyruvate is converted
to ethanol in two steps, with the first releasing
CO2
• Alcohol fermentat...
Figure 9.17
2 ADP 2 ATP
Glucose Glycolysis
2 Pyruvate
2 CO2
2
+
2 NADH
2 Ethanol 2 Acetaldehyde
(a) Alcohol fermentation (...
2 ADP + 2 P i 2 ATP
Glucose Glycolysis
2 Pyruvate
2 CO2
2 NAD
+
2 NADH
2 Ethanol 2 Acetaldehyde
(a) Alcohol fermentation
+...
• In lactic acid fermentation, pyruvate is reduced
to NADH, forming lactate as an end product,
with no release of CO2
• La...
(b) Lactic acid fermentation
2 Lactate
2 Pyruvate
2 NADH
Glucose Glycolysis
2 ADP + 2 P i 2 ATP
2 NAD
+
+
2 H+
Figure 9.17b
Comparing Fermentation with Anaerobic
and Aerobic Respiration
• All use glycolysis (net ATP = 2) to oxidize glucose
and ha...
• Obligate anaerobes carry out fermentation or
anaerobic respiration and cannot survive in the
presence of O2
• Yeast and ...
Figure 9.18
Glucose
CYTOSOL
Glycolysis
Pyruvate
No O2 present:
Fermentation
O2 present:
Aerobic cellular
respiration
Ethan...
The Evolutionary Significance of Glycolysis
• Ancient prokaryotes are thought to have used
glycolysis long before there wa...
Concept 9.6: Glycolysis and the citric acid
cycle connect to many other metabolic
pathways
• Gycolysis and the citric acid...
The Versatility of Catabolism
• Catabolic pathways funnel electrons from many
kinds of organic molecules into cellular
res...
• Fats are digested to glycerol (used in
glycolysis) and fatty acids (used in generating
acetyl CoA)
• Fatty acids are bro...
Figure 9.19
CarbohydratesProteins
Fatty
acids
Amino
acids
Sugars
Fats
Glycerol
Glycolysis
Glucose
Glyceraldehyde 3- P
NH3 ...
Biosynthesis (Anabolic Pathways)
• The body uses small molecules to build other
substances
• These small molecules may com...
Regulation of Cellular Respiration via
Feedback Mechanisms
• Feedback inhibition is the most common
mechanism for control
...
Figure 9.20
Phosphofructokinase
Glucose
Glycolysis
AMP
Stimulates
−
−
+
Fructose 6-phosphate
Fructose 1,6-bisphosphate
Pyr...
Figure 9.UN06
Inputs Outputs
Glucose
Glycolysis
2 Pyruvate + 2 ATP + 2 NADH
Figure 9.UN07
Inputs Outputs
2 Pyruvate 2 Acetyl CoA
2 Oxaloacetate
Citric
acid
cycle
2
26
8ATP NADH
FADH2
CO2
Figure 9.UN08
Protein complex
of electron
carriers
(carrying electrons from food)
INTERMEMBRANE
SPACE
MITOCHONDRIAL MATRIX...
Figure 9.UN09
INTER-
MEMBRANE
SPACE
H+ADP + P i
MITO-
CHONDRIAL
MATRIX
ATP
synthase
H+
ATP
Figure 9.UN10
Time
pHdifference
acrossmembrane
Figure 9.UN11
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Ch 9: Cell Respiration and Fermentation

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Ch 9: Cell Respiration and Fermentation

  1. 1. LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick Cellular Respiration and Fermentation Chapter 9
  2. 2. Overview: Life Is Work • Living cells require energy from outside sources • Some animals, such as the chimpanzee, obtain energy by eating plants, and some animals feed on other organisms that eat plants © 2011 Pearson Education, Inc.
  3. 3. Figure 9.1
  4. 4. • Energy flows into an ecosystem as sunlight and leaves as heat • Photosynthesis generates O2 and organic molecules, which are used in cellular respiration • Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work © 2011 Pearson Education, Inc.
  5. 5. Figure 9.2 Light energy ECOSYSTEM Photosynthesis in chloroplasts Cellular respiration in mitochondria CO2 + H2O + O2 Organic molecules ATP powers most cellular work ATP Heat energy
  6. 6. Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels • Several processes are central to cellular respiration and related pathways © 2011 Pearson Education, Inc.
  7. 7. Catabolic Pathways and Production of ATP • The breakdown of organic molecules is exergonic • Fermentation is a partial degradation of sugars that occurs without O2 • Aerobic respiration consumes organic molecules and O2 and yields ATP • Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2 © 2011 Pearson Education, Inc.
  8. 8. • Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration • Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat) © 2011 Pearson Education, Inc.
  9. 9. Redox Reactions: Oxidation and Reduction • The transfer of electrons during chemical reactions releases energy stored in organic molecules • This released energy is ultimately used to synthesize ATP © 2011 Pearson Education, Inc.
  10. 10. The Principle of Redox • Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions • In oxidation, a substance loses electrons, or is oxidized • In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) © 2011 Pearson Education, Inc.
  11. 11. Figure 9.UN01 becomes oxidized (loses electron) becomes reduced (gains electron)
  12. 12. Figure 9.UN02 becomes oxidized becomes reduced
  13. 13. • The electron donor is called the reducing agent • The electron receptor is called the oxidizing agent • Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds • An example is the reaction between methane and O2 © 2011 Pearson Education, Inc.
  14. 14. Figure 9.3 Reactants Products Energy WaterCarbon dioxideMethane (reducing agent) Oxygen (oxidizing agent) becomes oxidized becomes reduced
  15. 15. Oxidation of Organic Fuel Molecules During Cellular Respiration • During cellular respiration, the fuel (such as glucose) is oxidized, and O2 is reduced © 2011 Pearson Education, Inc.
  16. 16. Figure 9.UN03 becomes oxidized becomes reduced
  17. 17. Stepwise Energy Harvest via NAD+ and the Electron Transport Chain • In cellular respiration, glucose and other organic molecules are broken down in a series of steps • Electrons from organic compounds are usually first transferred to NAD+ , a coenzyme • As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration • Each NADH (the reduced form of NAD+ ) represents stored energy that is tapped to synthesize ATP © 2011 Pearson Education, Inc.
  18. 18. Figure 9.4 Nicotinamide (oxidized form) NAD+ (from food) Dehydrogenase Reduction of NAD+ Oxidation of NADH Nicotinamide (reduced form) NADH
  19. 19. Figure 9.UN04 Dehydrogenase
  20. 20. • NADH passes the electrons to the electron transport chain • Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction • O2 pulls electrons down the chain in an energy- yielding tumble • The energy yielded is used to regenerate ATP © 2011 Pearson Education, Inc.
  21. 21. Figure 9.5 (a) Uncontrolled reaction (b) Cellular respiration Explosive release of heat and light energy Controlled release of energy for synthesis of ATP Freeenergy,G Freeenergy,G H2 + 1 /2 O2 2 H + 1 /2 O2 1 /2 O2 H2O H2O 2 H+ + 2 e− 2 e− 2 H+ ATP ATP ATP Electrontransport chain (from food via NADH)
  22. 22. The Stages of Cellular Respiration: A Preview • Harvesting of energy from glucose has three stages – Glycolysis (breaks down glucose into two molecules of pyruvate) – The citric acid cycle (completes the breakdown of glucose) – Oxidative phosphorylation (accounts for most of the ATP synthesis) © 2011 Pearson Education, Inc.
  23. 23. Figure 9.UN05 Glycolysis (color-coded teal throughout the chapter)1. Pyruvate oxidation and the citric acid cycle (color-coded salmon) 2. Oxidative phosphorylation: electron transport and chemiosmosis (color-coded violet) 3.
  24. 24. Figure 9.6-1 Electrons carried via NADH Glycolysis Glucose Pyruvate CYTOSOL MITOCHONDRION ATP Substrate-level phosphorylation
  25. 25. Figure 9.6-2 Electrons carried via NADH Electrons carried via NADH and FADH2 Citric acid cycle Pyruvate oxidation Acetyl CoA Glycolysis Glucose Pyruvate CYTOSOL MITOCHONDRION ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation
  26. 26. Figure 9.6-3 Electrons carried via NADH Electrons carried via NADH and FADH2 Citric acid cycle Pyruvate oxidation Acetyl CoA Glycolysis Glucose Pyruvate Oxidative phosphorylation: electron transport and chemiosmosis CYTOSOL MITOCHONDRION ATP ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation
  27. 27. • The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions © 2011 Pearson Education, Inc. BioFlix: Cellular Respiration
  28. 28. • Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration • A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation • For each molecule of glucose degraded to CO2 and water by respiration, the cell makes up to 32 molecules of ATP © 2011 Pearson Education, Inc.
  29. 29. Figure 9.7 Substrate Product ADP P ATP Enzyme Enzyme
  30. 30. Concept 9.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate • Glycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvate • Glycolysis occurs in the cytoplasm and has two major phases – Energy investment phase – Energy payoff phase • Glycolysis occurs whether or not O2 is present © 2011 Pearson Education, Inc.
  31. 31. Figure 9.8 Energy Investment Phase Glucose 2 ADP + 2 P 4 ADP + 4 P Energy Payoff Phase 2 NAD+ + 4 e− + 4 H+ 2 Pyruvate + 2 H2O 2 ATP used 4 ATP formed 2 NADH + 2 H+ Net Glucose 2 Pyruvate + 2 H2O 2 ATP 2 NADH + 2 H+ 2 NAD+ + 4 e− + 4 H+ 4 ATP formed − 2 ATP used
  32. 32. Figure 9.9-1 Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate ADP Hexokinase 1
  33. 33. Figure 9.9-2 Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate Fructose 6-phosphate ADP Hexokinase Phosphogluco- isomerase 1 2
  34. 34. Figure 9.9-3 Glycolysis: Energy Investment Phase ATP ATP Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate ADP ADP Hexokinase Phosphogluco- isomerase Phospho- fructokinase 1 2 3
  35. 35. Figure 9.9-4 Glycolysis: Energy Investment Phase ATP ATP Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate To step 6 ADP ADP Hexokinase Phosphogluco- isomerase Phospho- fructokinase Aldolase Isomerase 1 2 3 4 5
  36. 36. Figure 9.9-5 Glycolysis: Energy Payoff Phase 2 NADH 2 NAD+ +2 H+ 2 P i 1,3-Bisphospho- glycerate6 Triose phosphate dehydrogenase
  37. 37. Figure 9.9-6 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD+ +2 H+ 2 P i 2 ADP 1,3-Bisphospho- glycerate 3-Phospho- glycerate 2 Phospho- glycerokinase 6 7 Triose phosphate dehydrogenase
  38. 38. Figure 9.9-7 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD+ +2 H+ 2 P i 2 ADP 1,3-Bisphospho- glycerate 3-Phospho- glycerate 2-Phospho- glycerate 2 2 Phospho- glycerokinase Phospho- glyceromutase 6 7 8 Triose phosphate dehydrogenase
  39. 39. Figure 9.9-8 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD+ +2 H+ 2 P i 2 ADP 1,3-Bisphospho- glycerate 3-Phospho- glycerate 2-Phospho- glycerate Phosphoenol- pyruvate (PEP) 2 2 2 2 H2O Phospho- glycerokinase Phospho- glyceromutase Enolase 6 7 8 9 Triose phosphate dehydrogenase
  40. 40. Figure 9.9-9 Glycolysis: Energy Payoff Phase 2 ATP 2 ATP 2 NADH 2 NAD+ +2 H+ 2 P i 2 ADP 1,3-Bisphospho- glycerate 3-Phospho- glycerate 2-Phospho- glycerate Phosphoenol- pyruvate (PEP) Pyruvate 2 ADP 2 2 2 2 H2O Phospho- glycerokinase Phospho- glyceromutase Enolase Pyruvate kinase 6 7 8 9 10 Triose phosphate dehydrogenase
  41. 41. Figure 9.9a Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate ADP Hexokinase 1 Fructose 6-phosphate Phosphogluco- isomerase 2
  42. 42. Figure 9.9b Glycolysis: Energy Investment Phase ATP Fructose 6-phosphate ADP 3 Fructose 1,6-bisphosphate Phospho- fructokinase 4 5 Aldolase Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate To step 6 Isomerase
  43. 43. Figure 9.9c Glycolysis: Energy Payoff Phase 2 NADH 2 ATP 2 ADP 2 2 2 NAD+ + 2 H+ 2 P i 3-Phospho- glycerate 1,3-Bisphospho- glycerate Triose phosphate dehydrogenase Phospho- glycerokinase 6 7
  44. 44. Figure 9.9d Glycolysis: Energy Payoff Phase 2 ATP 2 ADP 2222 2 H2O PyruvatePhosphoenol- pyruvate (PEP) 2-Phospho- glycerate 3-Phospho- glycerate 8 9 10 Phospho- glyceromutase Enolase Pyruvate kinase
  45. 45. Concept 9.3: After pyruvate is oxidized, the citric acid cycle completes the energy- yielding oxidation of organic molecules • In the presence of O2, pyruvate enters the mitochondrion (in eukaryotic cells) where the oxidation of glucose is completed © 2011 Pearson Education, Inc.
  46. 46. Oxidation of Pyruvate to Acetyl CoA • Before the citric acid cycle can begin, pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle • This step is carried out by a multienzyme complex that catalyses three reactions © 2011 Pearson Education, Inc.
  47. 47. Figure 9.10 Pyruvate Transport protein CYTOSOL MITOCHONDRION CO2 Coenzyme A NAD+ + H+ NADH Acetyl CoA 1 2 3
  48. 48. • The citric acid cycle, also called the Krebs cycle, completes the break down of pyruvate to CO2 • The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn © 2011 Pearson Education, Inc. The Citric Acid Cycle
  49. 49. Figure 9.11 Pyruvate NAD+ NADH + H+ Acetyl CoA CO2 CoA CoA CoA 2 CO2 ADP + P i FADH2 FAD ATP 3 NADH 3 NAD+ Citric acid cycle + 3 H+
  50. 50. • The citric acid cycle has eight steps, each catalyzed by a specific enzyme • The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate • The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle • The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain © 2011 Pearson Education, Inc.
  51. 51. Figure 9.12-1 1 Acetyl CoA Citrate Citric acid cycle CoA-SH Oxaloacetate
  52. 52. Figure 9.12-2 1 Acetyl CoA Citrate Isocitrate Citric acid cycle H2O 2 CoA-SH Oxaloacetate
  53. 53. Figure 9.12-3 1 Acetyl CoA Citrate Isocitrate α-Ketoglutarate Citric acid cycle NADH + H+ NAD+ H2O 3 2 CoA-SH CO2 Oxaloacetate
  54. 54. Figure 9.12-4 1 Acetyl CoA Citrate Isocitrate α-Ketoglutarate Succinyl CoA Citric acid cycle NADH NADH + H+ + H+ NAD+ NAD+ H2O 3 2 4 CoA-SH CO2 CoA-SH CO2 Oxaloacetate
  55. 55. Figure 9.12-5 1 Acetyl CoA Citrate Isocitrate α-Ketoglutarate Succinyl CoA Succinate Citric acid cycle NADH NADH ATP + H+ + H+ NAD+ NAD+ H2O ADP GTP GDP P i 3 2 4 5 CoA-SH CO2 CoA-SH CoA-SH CO2 Oxaloacetate
  56. 56. Figure 9.12-6 1 Acetyl CoA Citrate Isocitrate α-Ketoglutarate Succinyl CoA Succinate Fumarate Citric acid cycle NADH NADH FADH2 ATP + H+ + H+ NAD+ NAD+ H2O ADP GTP GDP P i FAD 3 2 4 5 6 CoA-SH CO2 CoA-SH CoA-SH CO2 Oxaloacetate
  57. 57. Figure 9.12-7 1 Acetyl CoA Citrate Isocitrate α-Ketoglutarate Succinyl CoA Succinate Fumarate Malate Citric acid cycle NADH NADH FADH2 ATP + H+ + H+ NAD+ NAD+ H2O H2O ADP GTP GDP P i FAD 3 2 4 5 6 7 CoA-SH CO2 CoA-SH CoA-SH CO2 Oxaloacetate
  58. 58. Figure 9.12-8 NADH 1 Acetyl CoA Citrate Isocitrate α-Ketoglutarate Succinyl CoA Succinate Fumarate Malate Citric acid cycle NAD+ NADH NADH FADH2 ATP + H+ + H+ + H+ NAD+ NAD+ H2O H2O ADP GTP GDP P i FAD 3 2 4 5 6 7 8 CoA-SH CO2 CoA-SH CoA-SH CO2 Oxaloacetate
  59. 59. Figure 9.12a Acetyl CoA Oxaloacetate Citrate Isocitrate H2O CoA-SH 1 2
  60. 60. Figure 9.12b Isocitrate α-Ketoglutarate Succinyl CoA NADH NADH NAD+ NAD+ + H+ CoA-SH CO2 CO2 3 4 + H+
  61. 61. Figure 9.12c Fumarate FADH2 CoA-SH6 Succinate Succinyl CoA FAD ADP GTP GDP P i ATP 5
  62. 62. Figure 9.12d Oxaloacetate8 Malate Fumarate H2O NADH NAD+ + H+ 7
  63. 63. Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis • Following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the energy extracted from food • These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation © 2011 Pearson Education, Inc.
  64. 64. The Pathway of Electron Transport • The electron transport chain is in the inner membrane (cristae) of the mitochondrion • Most of the chain’s components are proteins, which exist in multiprotein complexes • The carriers alternate reduced and oxidized states as they accept and donate electrons • Electrons drop in free energy as they go down the chain and are finally passed to O2, forming H2O © 2011 Pearson Education, Inc.
  65. 65. Figure 9.13 NADH FADH2 2 H+ + 1 /2 O2 2 e− 2 e− 2 e− H2O NAD+ Multiprotein complexes (originally from NADH or FADH2) I II III IV 50 40 30 20 10 0 Freeenergy(G)relativetoO2(kcal/mol) FMN Fe•S Fe•S FAD Q Cyt b Cyt c1 Cyt c Cyt a Cyt a3 Fe•S
  66. 66. • Electrons are transferred from NADH or FADH2 to the electron transport chain • Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O2 • The electron transport chain generates no ATP directly • It breaks the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts © 2011 Pearson Education, Inc.
  67. 67. Chemiosmosis: The Energy-Coupling Mechanism • Electron transfer in the electron transport chain causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space • H+ then moves back across the membrane, passing through the proton, ATP synthase • ATP synthase uses the exergonic flow of H+ to drive phosphorylation of ATP • This is an example of chemiosmosis, the use of energy in a H+ gradient to drive cellular work © 2011 Pearson Education, Inc.
  68. 68. Figure 9.14 INTERMEMBRANE SPACE Rotor Stator H+ Internal rod Catalytic knob ADP + P i ATP MITOCHONDRIAL MATRIX
  69. 69. Figure 9.15 Protein complex of electron carriers (carrying electrons from food) Electron transport chain Oxidative phosphorylation Chemiosmosis ATP synth- ase I II III IV Q Cyt c FADFADH2 NADH ADP + P i NAD+ H+ 2 H+ + 1 /2O2 H+ H+ H+ 21 H+ H2O ATP
  70. 70. • The energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis • The H+ gradient is referred to as a proton- motive force, emphasizing its capacity to do work © 2011 Pearson Education, Inc.
  71. 71. An Accounting of ATP Production by Cellular Respiration • During cellular respiration, most energy flows in this sequence: glucose → NADH → electron transport chain → proton-motive force → ATP • About 34% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 32 ATP • There are several reasons why the number of ATP is not known exactly © 2011 Pearson Education, Inc.
  72. 72. Figure 9.16 Electron shuttles span membrane MITOCHONDRION 2 NADH 2 NADH 2 NADH 6 NADH 2 FADH2 2 FADH2 or + 2 ATP+ 2 ATP + about 26 or 28 ATP Glycolysis Glucose 2 Pyruvate Pyruvate oxidation 2 Acetyl CoA Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis CYTOSOL Maximum per glucose: About 30 or 32 ATP
  73. 73. Concept 9.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen • Most cellular respiration requires O2 to produce ATP • Without O2, the electron transport chain will cease to operate • In that case, glycolysis couples with fermentation or anaerobic respiration to produce ATP © 2011 Pearson Education, Inc.
  74. 74. • Anaerobic respiration uses an electron transport chain with a final electron acceptor other than O2, for example sulfate • Fermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP © 2011 Pearson Education, Inc.
  75. 75. Types of Fermentation • Fermentation consists of glycolysis plus reactions that regenerate NAD+ , which can be reused by glycolysis • Two common types are alcohol fermentation and lactic acid fermentation © 2011 Pearson Education, Inc.
  76. 76. • In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO2 • Alcohol fermentation by yeast is used in brewing, winemaking, and baking © 2011 Pearson Education, Inc. Animation: Fermentation Overview
  77. 77. Figure 9.17 2 ADP 2 ATP Glucose Glycolysis 2 Pyruvate 2 CO2 2 + 2 NADH 2 Ethanol 2 Acetaldehyde (a) Alcohol fermentation (b) Lactic acid fermentation 2 Lactate 2 Pyruvate 2 NADH Glucose Glycolysis 2 ATP2 ADP+ 2 P i NAD 2 H+ + 2 P i 2 NAD++ + 2 H+
  78. 78. 2 ADP + 2 P i 2 ATP Glucose Glycolysis 2 Pyruvate 2 CO2 2 NAD + 2 NADH 2 Ethanol 2 Acetaldehyde (a) Alcohol fermentation + 2 H+ Figure 9.17a
  79. 79. • In lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2 • Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt • Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce © 2011 Pearson Education, Inc.
  80. 80. (b) Lactic acid fermentation 2 Lactate 2 Pyruvate 2 NADH Glucose Glycolysis 2 ADP + 2 P i 2 ATP 2 NAD + + 2 H+ Figure 9.17b
  81. 81. Comparing Fermentation with Anaerobic and Aerobic Respiration • All use glycolysis (net ATP = 2) to oxidize glucose and harvest chemical energy of food • In all three, NAD+ is the oxidizing agent that accepts electrons during glycolysis • The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O2 in cellular respiration • Cellular respiration produces 32 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule © 2011 Pearson Education, Inc.
  82. 82. • Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O2 • Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration • In a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes © 2011 Pearson Education, Inc.
  83. 83. Figure 9.18 Glucose CYTOSOL Glycolysis Pyruvate No O2 present: Fermentation O2 present: Aerobic cellular respiration Ethanol, lactate, or other products Acetyl CoA MITOCHONDRION Citric acid cycle
  84. 84. The Evolutionary Significance of Glycolysis • Ancient prokaryotes are thought to have used glycolysis long before there was oxygen in the atmosphere • Very little O2 was available in the atmosphere until about 2.7 billion years ago, so early prokaryotes likely used only glycolysis to generate ATP • Glycolysis is a very ancient process © 2011 Pearson Education, Inc.
  85. 85. Concept 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways • Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways © 2011 Pearson Education, Inc.
  86. 86. The Versatility of Catabolism • Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration • Glycolysis accepts a wide range of carbohydrates • Proteins must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycle © 2011 Pearson Education, Inc.
  87. 87. • Fats are digested to glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA) • Fatty acids are broken down by beta oxidation and yield acetyl CoA • An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate © 2011 Pearson Education, Inc.
  88. 88. Figure 9.19 CarbohydratesProteins Fatty acids Amino acids Sugars Fats Glycerol Glycolysis Glucose Glyceraldehyde 3- P NH3 Pyruvate Acetyl CoA Citric acid cycle Oxidative phosphorylation
  89. 89. Biosynthesis (Anabolic Pathways) • The body uses small molecules to build other substances • These small molecules may come directly from food, from glycolysis, or from the citric acid cycle © 2011 Pearson Education, Inc.
  90. 90. Regulation of Cellular Respiration via Feedback Mechanisms • Feedback inhibition is the most common mechanism for control • If ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down • Control of catabolism is based mainly on regulating the activity of enzymes at strategic points in the catabolic pathway © 2011 Pearson Education, Inc.
  91. 91. Figure 9.20 Phosphofructokinase Glucose Glycolysis AMP Stimulates − − + Fructose 6-phosphate Fructose 1,6-bisphosphate Pyruvate Inhibits Inhibits ATP Citrate Citric acid cycle Oxidative phosphorylation Acetyl CoA
  92. 92. Figure 9.UN06 Inputs Outputs Glucose Glycolysis 2 Pyruvate + 2 ATP + 2 NADH
  93. 93. Figure 9.UN07 Inputs Outputs 2 Pyruvate 2 Acetyl CoA 2 Oxaloacetate Citric acid cycle 2 26 8ATP NADH FADH2 CO2
  94. 94. Figure 9.UN08 Protein complex of electron carriers (carrying electrons from food) INTERMEMBRANE SPACE MITOCHONDRIAL MATRIX H+ H+ H+ 2 H+ + 1 /2 O2 H2O NAD+ FADH2 FAD Q NADH I II III IV Cyt c
  95. 95. Figure 9.UN09 INTER- MEMBRANE SPACE H+ADP + P i MITO- CHONDRIAL MATRIX ATP synthase H+ ATP
  96. 96. Figure 9.UN10 Time pHdifference acrossmembrane
  97. 97. Figure 9.UN11

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