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Chapter 9
Cellular Respiration
I. Catabolic Pathways Yield Energy
A. Cellular Respiration1. C6H12O6 + 6O2 6CO2 + 6H2O
2. Exergonic
3. ATP production is the benefit for the cell
B. Redox Reactions: Transfer electrons from one reactant to another reactant
1. Oxidation: Substance loses electrons (Na)
2. Reduction: Substance gains electrons (Cl)
3. Electronegativity: An atoms ability to attract electrons to itself (Cl)
4. Energy is released when an electron changes location.
C. Redox Reactions when electrons are shared.
1. Some redox reactions change the degree to which electrons are shared.
2. Methane Example
CH4
H
H
HH CO O O O OC
H H
Methane(reducingagent)
Oxygen(oxidizingagent)
Carbon dioxide Water
+ 2O2 CO2 + Energy + 2 H2O
becomes oxidized
becomes reduced
Reactants Products
Figure 9.3
3. Cellular respiration is similar.a) C6H12O6 + 6O2 6CO2 + 6H2O
b) Hydrogens are transferred to Oxygen
c) More importantly, hydrogen’s electrons move away from it and closer to oxygen
d) Much energy is released in this motion
D. NAD+ and Energy harvest from e-
1. Hydrogen does not immediately join Oxygen to form water. (C6H12O6 + O2 CO2 H2O)
2. NAD+: (Nicotinamide adenine dinucleotide)a) Allows e- energy to be harvested slowly.
(a) Uncontrolled reaction
Fre
e en
ergy
, G
H2O
Explosiverelease of
heat and lightenergy
Figure 9.5 A
H2 + 1/2 O2
3. NAD+: (Nicotinamide adenine dinucleotide)a) Allows e- energy to be harvested slowly.
i. NAD+ strips 2 e-s from glucose
ii. Along with them come 2 hydrogens (NADH + H+)
iii. Very little energy is lost from the electrons here.
iv. The 2e- s can be passed to other molecules to release E. to make ATP
2H+
OH2O
ATP
ATP
ATP
E. The Stages of Cellular Respiration 1. Glycolysis
» Glucose (6C)Pyruvate(3C) » in Cytoplasm
2. Citric Acid Cycle» products of glycolysis broken down to CO2
» inside mitochondria
3. Electron Transport: (Oxidative Phosphorylation)
» High Energy Electrons from 1 and 2 passed down a chain of molecules to produce H2O.
» The energy released in the chain is used to make ATP via (oxidative phosphorylation)
F. Substrate-Level Phosphorylation: Adding a phosphate to ADP to make ATP1. phosphate from an organic molecule rather than
free floating.
Figure 9.7
Enzyme Enzyme
ATP
ADP
Product
SubstrateP
+
CH2O P
Glucose-6-phosphate
Glyceraldehyde-3-phosphate
II. GlycolysisC
Glucose
Hexokinase1
PA P P
PA P P
O
CH2O PC
Fructose-6-phosphate
Phosphoglucoisomerase 2
PO
CH2P CH2O O
Fructose-1,6-bisphosphate
Phosphofructokinase3
CP O
C=O
C PCH2 O
C=O
C
Aldolase4
Isomerase5
Glyceraldehyde-3-phosphate
PCH2 O
C=O
C
Dihydroxyacetone Phosphate
PCH2 O
C=O
C
Glyceraldehyde-3-phosphate
PCH2 O
C=O
C
P O
1,3-Bisphosphoglycerate
Triose phosphate dehydrogenase
6
PCH2 O
C=O
C
3-Phosphoglycerate
P
C
O
C=O
C
Phosphoenolpyruvate
C
C=O
C=O
Pyruvate
P
A P P
P
Phosphoglycerokinase7
P
A P P
P
C
O
C=O
C
2-Phosphoglycerate
Phosphoglyceromutase8
Enolase9
Pyruvate Kinase10
III. Citric Acid CycleA. Preparation
1. Pyruvate enters mitochondria
2. If oxygen is present cell resp. proceeds.
3. Acetyl CoA produced1. CO2 removed
2. Oxidation by NAD+
3. Coenzyme A attached to remaining two carbons.
4. Acetyl CoA enters the Citric Acid Cycle
Coenzyme AC
C=O
C=O
Pyruvate
O-
C
C=O
CoANAD+ NADH + H+
CO2
ATP
2 CO2
3 NAD+
3 NADH
+ 3 H+
ADP + P i
FAD
FADH2
Citricacidcycle
CoA
CoA
Acetyle CoA
NADH
+ 3 H+
CoA
CO2
Pyruvate(from glycolysis,2 molecules per glucose)
ATP ATP ATP
Glycolysis Citricacidcycle
Oxidativephosphorylation
Figure 9.11
C
C=O
CoA
Acetyl CoA
COO-
O=C
C
COO-
Oxaloacetate
COO-
HO-C
C
COO-
C
COO-
Citrate
COO-
C COO-
C
COO-
HO-C
Isocitrate
COO-
C
C
COO-
O=C
α-Ketogluterate
C
C
COO-
O=C
CoASuccinyl CoAC
C
COO-
COO-
Succinate
C
C
COO-
COO-
Fumarate
C
HO-C
COO-
COO-
Malate
COO-
O=C
C
COO-
Oxaloacetate
H2O
H2O
CO2
NAD+
NADH + H+
CO2
NAD+NADH+ H+
CoA
CoA
AP P
P
PAP P
FAD
FADH2H2O
NAD+
NADH+ H+
Acetyl CoA
NADH
Oxaloacetate
CitrateMalate
Fumarate
Succinate
SuccinylCoA
-Ketoglutarate
Isocitrate
Citricacidcycle
S CoA
CoA SH
NADH
NADH
FADH2
FAD
GTP GDP
NAD+
ADP
P i
NAD+
CO2
CO2
CoA SH
CoA SH
CoAS
H2O
+ H+
+ H+ H2O
C
CH3
O
O C COO–
CH2
COO–
COO–
CH2
HO C COO–
CH2
COO–
COO–
COO–
CH2
HC COO–
HO CH
COO–
CH
CH2
COO–
HO
COO–
CH
HC
COO–
COO–
CH2
CH2
COO–
COO–
CH2
CH2
C O
COO–
CH2
CH2
C O
COO–
1
2
3
4
5
6
7
8NAD+
+ H+
ATP
Figure 9.12
Results of CAC (one turn)
ATP = NADH = FADH2 =CO2 =
131
2
C
C=O
CoA
Acetyl CoA
COO-
O=C
C
COO-
Oxaloacetate
COO-
HO-C
C
COO-
C
COO-
Citrate
COO-
C COO-
C
COO-
HO-C
Isocitrate
COO-
C
C
COO-
O=C
α-Ketogluterate
C
C
COO-
O=C
CoASuccinyl CoAC
C
COO-
COO-
Succinate
C
C
COO-
COO-
Fumarate
C
HO-C
COO-
COO-
Malate
CoA
CoA
CoA
H2O
H2O
CO2
CO2 NAD+
NAD+
NAD+
NADH+ H+
NADH+ H+
NADH+ H+
FADFADH2 PAP P
P
AP P
IV. Electron Transport, Oxidative Phosphorylation and Chemiosmosis
A. Structure of Mitochondria Matrix: Juice. Site
of Citric acid cycle.
A. Cristae: Folds in the inner memebrane. Site of electron
transport.
B. Intermembrane space:
B. Electron Transport Overview: The following animation and diagram are an overview of the process. Definitions will follow.
-Oxidative Phosphorilation: ATP production using energy derived from redox reactions.
NADH
Outer Membrane
H+
Inner Membrane
Intermembrane Space
Matrix
H+
H+
FADH2FAD
OH2O
Complex 1
Complex 2
Complex
3
Complex 4
NAD+
ADP
PATP
ATP Synthase
ubiquinone
NADH
Outer Membrane
H+
Inner Membrane
Intermembrane Space
MatrixH+
H+
O
H2O
Complex 1
Complex 2
Complex 3
Complex 4
NAD+
ADP + P
ATP
2e -
2e-
2e-
2e- 2e -
H+
H+
H+
H+H+
H+
H+
H+ H+
ATP Synthase
ubiquinone
FAD
Outer Membrane
H+
Inner Membrane
Intermembrane Space
Matrix
H+
O
H2O
Complex 1
Complex 2
Complex 3
Complex 4
FADH2
ADP + P
ATP
2e-
2e-
2e- 2e -
H+
H+
H+H+
H+
H+
H+ H+
ATP Synthase2e
-
C. Chemiosmosis:1. The process of electron transport makes no
ATP directly.
2. Electron transport creates a H+ gradient.a. Results in high H+ amounts in the intermembrane
space.
b. This is like water build up behind a dam. It has a lot of potential energy.
c. Proton-motive force: The name given to the gradient. i. The force tries to push the protons back across the
membrane to reach equilibrium.
d. Chemiosmosis: Using energy stored in the H+ gradient across a membrane to synthesize ATP.
D. ATP Synthase: The enzyme that makes the ATP
1. ATP synthase is the only place protons can go back through the membrane
INTERMEMBRANE SPACE
H+
H+
H+
H+
H+
H+ H+
H+
P i
+ADP
ATP
A rotor within the membrane spins clockwise whenH+ flows past it down the H+
gradient.
A stator anchoredin the membraneholds the knobstationary.
A rod (for “stalk”)extending into the knob alsospins, activatingcatalytic sites inthe knob.
Three catalytic sites in the stationary knobjoin inorganic Phosphate to ADPto make ATP.
MITOCHONDRIAL MATRIXFigure 9.14
E. Energy Totals for Cellular Respiration1. ATP Formed
– Glycolysis = 2
– Pyruvate Oxydation = 0
– CAC = 2
2. NADH Generated
– Glycolysis = 2
– Pyruvate OXydation = 2
– CAC = 6
– ATP/ NADH = 3
– Total ATP from all NADH = 30
3. FADH2 Generated
– Glycolysis = 0
– Pyruvate Oxydation = 0
– CAC= 2
– ATP generated per FADH2 = 2
– Total ATP from FADH2 = 4
• Total ATP from catabolism of one glucose = 38 sometimes 36
V. Fermentation: Production of ATP from glucose when no oxygen is present (Anaerobic)
A. General Rules:1. Cellular respiration can’t happen w/o oxygen
2. Fermentation allows us to make ATP anyway.
3. Glycolysis makes 2 ATP by subtrate level phosphorilation. a. If done rapidly this could be enough to get by
b. The limiting factor is the amount of available NAD+ available.
4. Fermentation allows glycolysis to continue by oxidizing the NADH for reuse.
B. Types: 1. Alcohol Fermentation: Pyruvate is converted to
ethanol.– Often used by bacteria and yeast
– Step 1: Pyruvate releases 2CO2 Acetaldehyde
– Step 2: Acetaldehyde oxidizes NADH ethanol and NAD+
2 ADP + 2 P1 2 ATP
GlycolysisGlucose
2 NAD+ 2 NADH
2 Pyruvate
2 Acetaldehyde 2 Ethanol
(a) Alcohol fermentation
H
H OH
CH3
C
O –
OC
C O
CH3
H
C O
CH3
CO22
2 ADP + 2 P1 2 ATP
GlycolysisGlucose
2 NAD+ 2 NADH
2 Pyruvate
2 Acetaldehyde 2 Ethanol
(a) Alcohol fermentation
2 ADP + 2 P1 2 ATP
GlycolysisGlucose
2 NAD+ 2 NADH
2 Lactate
(b) Lactic acid fermentation
H
H OH
CH3
C
O –
OC
C O
CH3
H
C O
CH3
O–
C O
C O
CH3O
C O
C OHH
CH3
CO22
Figure 9.17
2. Lactic Acid Fermentation1. Happens in human muscles as well as bacteria that
make cheese.
2. One Step: Pyruvate oxidizes NADH NAD+ + Lactic Acid.
c. Comparing Fermentation and Cellular Respiration
Cellular Respiration1.Aerobic2.38 ATP produced3.NADH oxidized to produce H20
Fermentation1.Anaerobic2.2 ATP produced3.NADH oxidized to make ethanol or lactate