1. Cellular Respiration

2. Cellular Respiration – AKA Respiration
The metabolic pathways by which carbohydrates are broken down into ATP
The formula for respiration is:
C6H12O6 + 6O2  6CO2 + 6 H2O + ATP
Respiration allows the gradual build up of ATP,
If a cell used all the potential energy in glucose at once, too much heat would be released, and not all the energy would be harvested.

3. Three Steps of Respiration
1. Glycolysis
Yields 2 molecules of ATP
2. Citric Acid Cycle (Krebs Cycle)
3. Electron Transport Chain (Oxidative phosphorylation)
Yields 32 molecules of ATP
Though 36 molecules of ATP are produced, it is only 39% of the total energy in a molecule of glucose

4. The Process in General Electrons carried via NADH and FADH2 Oxidative
phosphorylation:
electron transport
and
chemiosmosis
0 %
Citric
acid
cycle
Glycolysis
Glucose
Pyruvate
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation

5. Glycolysis Glyco- of or relating to glucose Lysis- to split or burst
Changes one molecule of glucose to 2 three Carbon molecules called pyruvate
Occurs in the cytosol (cytoplasm)
Does not require Oxygen

6. Glycolysis Glucose  2 pyruvate 2 NAD  2 NADH 2 ADP 2 ATP 
Net gain of 2 ATP molecules (top=input, bottom= outputs)
GlucoseFructosePGALPGAPEPpyruvate
4 ATP
2 ATP  2ADP
P + 2NAD2NADH
2 ATP
H2O
2 ATP

7. Glycolysis
When Oxygen is present, glucose / pyruvate can be broken down further in a process called the Krebs cycle.
However, when Oxygen is not present pyruvate can be broken down through the process of fermentation.
Aerobic respiration- respiration with Oxygen
Anaerobic respiration- respiration with out Oxygen

8. The Evolutionary Significance of Glycolysis
Glycolysis occurs in nearly all organisms
Glycolysis probably evolved in ancient prokaryotes before there was oxygen in the atmosphere
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9. Fermentation
Glycolysis + the reduction of pyruvate to lactic acid, alcohol, or CO2
Fermentation is inefficient. But when O2 is not present it is better than nothing.
Glycolysis yields 2 ATP, fermentation yields 2 more
Fermentation yields only 14.6 Kcal of a possible 686Kcal from 1 molecule of glucose that is about 2.1% efficient.

10. Fermentation In yeast produces alcohol and CO2  death
In humans produces lactic Acid  soreness
In athletes :
because of training more mitochondria are produced in the muscle cells.
b/c of higher # of mito., they utilize more O2 and can produce more ATP (less O2 wasted)
Means less Oxygen debt or deficit
Less fermentation
Less soreness

11. 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
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12. 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
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13. Fig. 9-18 Figure 9.18 Fermentation 2 ADP + 2 Pi 2 ATP Glucose
Glycolysis
2 Pyruvate
2 NAD+
2 NADH 2
CO2
+ 2 H+
2 Ethanol
2 Acetaldehyde
(a) Alcohol fermentation
2 ADP + 2 Pi
2 ATP
Glucose
Glycolysis
Figure 9.18 Fermentation
2 NAD+
2 NADH
+ 2 H+
2 Pyruvate
2 Lactate
(b) Lactic acid fermentation

14. (a) Alcohol fermentation
Fig. 9-18a
2 ADP + 2 P
2 ATP i
Glucose
Glycolysis
2 Pyruvate
2 NAD+
2 NADH 2
CO2
+ 2 H+
Figure 9.18a Fermentation
2 Acetaldehyde
2 Ethanol
(a) Alcohol fermentation

15. 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
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16. (b) Lactic acid fermentation
Fig. 9-18b
2 ADP + 2 P
2 ATP i
Glucose
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 Pyruvate
Figure 9.18b Fermentation
2 Lactate
(b) Lactic acid fermentation

17. Fermentation and Aerobic Respiration Compared
Both processes use glycolysis to oxidize glucose and other organic fuels to pyruvate
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 38 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

18. 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
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19. Ethanol or lactate Citric acid cycle
Fig. 9-19
Glucose
Glycolysis
CYTOSOL
Pyruvate
O2 present:
Aerobic cellular
respiration
No O2 present:
Fermentation
MITOCHONDRION
Ethanol or
lactate
Acetyl CoA
Figure 9.19 Pyruvate as a key juncture in catabolism
Citric
acid
cycle

20. Aerobic Respiration Occurs when Oxygen is present
Produces 36 ATP molecules
Begins after glycolysis
The Transition reaction connects glycolysis to the Aerobic pathways (Krebs cycle & Electron transport chain).

21. Transition Reactions Connects glycolysis to the Krebs cycle
The pyruvate from glycolysis is converted to a 2 Carbon compound called an acetyl group.
The acetyl group is attached to Coenzyme A
The resulting complex is Acetyl Coenzyme A (Acetyl CoA)
Coenzyme- protein that acts as a carrier molecule in biochemical processes.
This process releases CO2

22. Transition Reaction Occurs twice for each glucose molecule
Occurs in the matrix of the mitochondria
2 pyruvate + 2 CoA  2 Acetyl CoA + 2 CO2
Mitochondrial structure
Cristae - location of the electron transport chain
Cytosol – location of glycolysis
Matrix- location of the transition reactions and the Krebs cycle.
2 NAD  2 NADH + H-

23. CYTOSOL MITOCHONDRION NAD+ NADH + H+ 2 1 3 Acetyl CoA Pyruvate
Fig. 9-10
CYTOSOL
MITOCHONDRION
NAD+
NADH
+ H+ 2 1 3
Acetyl CoA
Figure 9.10 Conversion of pyruvate to acetyl CoA, the junction between glycolysis and the citric acid cycle
Pyruvate
Coenzyme A
CO2
Transport protein

24. Krebs Cycle
The products of the Transition RXN are the reactants of the Krebs Cycle.
The Krebs Cycle is also known as the Citric Acid Cycle. Citrate is the first metabolite produced in the Krebs Cycle.
During the Krebs Cycle:
the acetyl group on Acetyl CoA is oxidized to CO2.
Some of the electrons (H ions) are accepted by NAD,
but 1 is picked up by another electron carrier, FAD.
Some ATP is produced by phosphorylation like in glycolysis.
The Krebs Cycle turns twice for each original molecule of glucose.

25. Krebs Cycle Inputs Outputs 2 acetyl groups 2 ADP + 2 P 6 NAD 2 FAD
4 CO2
2 ATP
6 NADH
2FADH2
See Figure 9.7

26. Citric acid cycle Succinyl CoA
Acetyl CoA
CoA—SH
NADH
H2O
NAD+
Oxaloacetate
Isocitrate
Malate
Citrate
NAD+
Citric
acid
cycle
NADH
CO2
H2O
Fumarate
CoA—SH
-Keto-
glutarate
CoA—SH
FADH2
CO2
NAD+
FAD
Succinate
NADH P
Succinyl
CoA
ADP
ATP

27. Substrate-level phosphorylation:
Fig. 9-7
Substrate-level phosphorylation:
Use of an enzyme to produce ATP and another product
Enzyme
Enzyme +
ADP
Figure 9.7 Substrate-level phosphorylation P
Substrate
ATP
Product

28. The Electron Transport Chain
Located in the cristae
Series of electron carriers that pass an electron from one to another.
The electrons in the electron transport chain come from NADH and FADH2 in the Krebs Cycle
Drives the process that generates most of the ATP .
The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions

29. The electron transport chain generates no ATP
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
The chain’s function is to break the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts
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30. Figure 9.13 Free-energy change during electron transport
NADH 50 2 e–
NAD+
FADH2 2 e–
FAD
Multiprotein
complexes  40
FMN
FAD
Fe•S 
Fe•S Q

Cyt b
Fe•S 30
Cyt c1 IV
Free energy (G) relative to O2 (kcal/mol)
Cyt c
Cyt a
Cyt a3 20
Figure 9.13 Free-energy change during electron transport e– 10 2
(from NADH
or FADH2)
2 H+ + 1/2 O2
H2O

31. 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 channels in 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

32. 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
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33. i INTERMEMBRANE SPACE H+ Stator Rotor Internal rod Cata- lytic knob
Fig. 9-14
INTERMEMBRANE SPACE H+
Stator
Rotor
Internal
rod
Figure 9.14 ATP synthase, a molecular mill
Cata-
lytic
knob
ADP + P
ATP i
MITOCHONDRIAL MATRIX

34. Oxidative Phosphorylation
The process by which ATP production is tied to an electron transport system that uses Oxygen as a final electron receptor.
After Oxygen accepts the electron it binds with Hydrogen from the matrix and form H2O
Figure 9.8

35. Complexes of the Electron Transport Chain
NADH dehydrogenase - causes the oxidation of NADH.
Cytochrome b-c complex - the complex which receives electrons and pumps H ions into the inter-membrane space.
Cytochrome oxidase complex - receives electrons and passes them to oxygen.

36. Electron Transport Chain

37. The Process in General Electrons carried via NADH Electrons carried
via NADH and
FADH2
0 %
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
Citric
acid
cycle
Glycolysis
Glucose
Pyruvate
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation

38. The process with details
Electron shuttles
span membrane
2 NADH
MITOCHONDRION or
CYTOSOL
2 FADH2
2 NADH
2 NADH
6 NADH
2 FADH2
Glycolysis
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
Citric
acid
cycle 2
Acetyl
CoA 2
Pyruvate
Glucose
+ 2 ATP
+ 2 ATP
+ about 32 or 34 ATP
Maximum per glucose:
About
36 or 38 ATP

39. 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
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40. 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
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41. Fatty acids are broken down by beta oxidation and yield acetyl CoA
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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

42. Citric acid cycle Oxidative phosphorylation
Fig. 9-20
Proteins
Carbohydrates
Fats
Amino
acids
Sugars
Glycerol
Fatty
acids
Glycolysis
Glucose
Glyceraldehyde-3- P
NH3
Pyruvate
Acetyl CoA
Figure 9.20 The catabolism of various molecules from food
Citric
acid
cycle
Oxidative
phosphorylation

43. 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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings