1. Overview Of Aerobic Cellular Respiration
Cellular respiration: the process that releases energy (ATP) by breaking down glucose and other food molecules in the presence of oxygen
3 phases
Glycolysis
Krebs cycle
The electron transport chain

2. Cellular Respiration

3. 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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

4. 2 e– + 2 H+ 2 e– + H+ Dehydrogenase Nicotinamide (reduced form)
Fig. 9-4
2 e– + 2 H+
2 e– + H+
NADH H+
Dehydrogenase
Reduction of NAD+
NAD+ +
2[H] + H+
Oxidation of NADH
Nicotinamide
(reduced form)
Nicotinamide
(oxidized form)
Figure 9.4 NAD+ as an electron shuttle

5. It starts… Cell Respiration starts with the food you eat.
Foods are mechanically and chemically broken down throughout your digestive system.
Amylase – Enzyme in saliva that breaks down starches

6. Step 1: Glyco-lysis: breaking glucose

7. Stage 1- Glycolysis (Glyco) and (lysis)- Breakdown of glucose
Occurs in the cytoplasm
Anaerobic (no oxygen required)
Breaks glucose into 2 molecules called pyruvate
2 ATPs required to start the reaction
4 ATPs are produced.
Net Gain = 2 ATPs

8. Substrate Level Phosphorylation
Fig. 9-7
Substrate Level Phosphorylation
Substrate-level phosphorylation is the enzyme catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate (substance) in catabolism.
IE: When an enzyme breaks a phosphate group off a molecule (substrate) and reattaches it to ADP to create ATP.
Enzyme
Enzyme
Figure 9.7 Substrate-level phosphorylation

9. Substrate Level Phosphorylation
Fig. 9-7
Substrate Level Phosphorylation
A small amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation .
Enzyme
Enzyme
Figure 9.7 Substrate-level phosphorylation

11. Butterflies
Walk your turtle through the process of Glycolysis

12. Review What 2 molecules are produced at the end of glycolysis?
How many carbons are in the two molecules produced at the end of glycolysis?

13. Objectives: Describe the major events in Glycolysis
Summarize the events of the Krebs Cycle
Distinguish between Glycolysis and Aerobic Respiration
Summarize the reactants and products of cellular respiration

14. Shoulder Partners

15. 7.2 The Krebs cycle and Electron Transport
Aerobic Respiration

16. Mitochondria

19. Krebs Cycle (Citric Acid Cycle)

20. Stage 2: Krebs Cycle Krebs cycle Takes place in matrix of mitochondria
The Krebs cycle occurs twice
Once for each pyruvate; twice for each glucose
Remember 2 pyruvate =1 glucose

21. The Krebs Cycle
Aerobic (requires oxygen)
Breaks pyruvic acid down
First, into Acetyl CoA
Then, into CO2 and Hydrogen
Yields 2 ATPs and high-energy electrons (NADH and FADH2) for the electron transport chain

22. Substrate Level Phosphorylation
Fig. 9-7
Substrate Level Phosphorylation
A small amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation .
Enzyme
Enzyme
Figure 9.7 Substrate-level phosphorylation

24. Turtles
Walk your butterfly through the process of the Krebs cycle

25. The E.T.C. (electron transport chain)

26. Step 3: The Electron Transport Chain
Occurs along the inner membrane of the mitochondria (Cristae)
Uses high-energy electrons from NADH and FADH2 (produced during the Krebs Cycle) to pump H+ from the matrix to the intermembrane space
Hydrogen electrons are transferred along the ETC to Oxygen (final electron acceptor)  Water

27. NADH and FADH2
NADH and FADH2 passes the electrons to the electron transport chain
O2 pulls electrons down the chain in an energy- yielding tumble
The energy yielded is used to regenerate ATP
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28. 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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

29. Oxidative Phosphorylation
The process of creating ATP using energy from redox reactions in the ETC
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

30. Oxidative Phosphorylation
The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions
Makes ~32 ATP
This requires the presence of Oxygen as the final electron acceptor
Accounts for 90% of ATP generated
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31. Electron transport chain 2 Chemiosmosis
Fig. 9-16 H+ H+ H+ H+
Protein complex
of electron
carriers
Cyt c V Q
 
ATP synthase 
2 H+ + 1/2O2
H2O
FADH2
FAD
NADH
NAD+
ADP + P
ATP
Figure 9.16 Chemiosmosis couples the electron transport chain to ATP synthesis i
(carrying electrons
from food) H+ 1
Electron transport chain 2
Chemiosmosis
Oxidative phosphorylation

32. 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 40% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 38 ATP
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

33. Fig. 9-17
CYTOSOL
Electron shuttles
span membrane
MITOCHONDRION
2 NADH or
2 FADH2
2 NADH
2 NADH
6 NADH
2 FADH2
Glycolysis
Oxidative
phosphorylation:
electron transport
and
chemiosmosis 2
Pyruvate 2
Acetyl
CoA
Citric
acid
cycle
Glucose
+ 2 ATP
+ 2 ATP
+ about 32 or 34 ATP
Figure 9.17 ATP yield per molecule of glucose at each stage of cellular respiration
About
36 or 38 ATP
Maximum per glucose:

34. That moment when…
Mitochondria goes from being the power house of the cell to being the oxidative phosphorylation center of the cell

35. Butterflies
Explain how the ETC runs to your turtles

36. Overall Cellular Respiration breaks down C6H12O6.
It produces H2O and CO2
It can produce ATPs Net Gain
2 GLYCOLYSIS
2 KREBS CYCLE
32-34 ETC

38. Cellular Respiration (aerobic)

39. Turtles
Walk your butterfly through the process of cellular respiration

40. Butterflies
Walk your turtle through the process of cellular respiration

41. What if there is no Oxygen?

42. Anaerobic respiration
Not enough oxygen for aerobic respiration
Fermentation-releases energy from food molecules by producing ATP in the absence of oxygen. (Anaerobic = no oxygen)
Two types: alcoholic fermentation, lactic acid fermentation

43. Lactic acid fermentation
Alcoholic fermentation
No oxygen
Occurs in muscles
Pyruvates lactate
Occurs so muscles can continue making ATP
Get lactate build up in muscles
Causes burning sensation
No oxygen
Pyruvate  carbon dioxide & ethanol
Seen in yeast and fungus
Used to make beverages, food, makes dough rise

44. Fermentation
Anaerobic respiration uses an electron transport chain with an electron acceptor other than O2, for example sulfate
Fermentation uses phosphorylation instead of an electron transport chain to generate ATP
Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis
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45. alcohol fermentation
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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

46. lactic acid fermentation
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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

47. Anaerobic Organisms
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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

48. 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

49. 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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50. 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
Fats are digested to glycerol (used in glycolysis) and fatty acids (used in generating 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

51. 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

52. 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

53. Figure 9.21 The control of cellular respiration
Glucose
AMP
Glycolysis
Fructose-6-phosphate
Stimulates +
Phosphofructokinase – –
Fructose-1,6-bisphosphate
Inhibits
Inhibits
Pyruvate
ATP
Citrate
Acetyl CoA
Figure 9.21 The control of cellular respiration
Citric
acid
cycle
Oxidative
phosphorylation