1. Cellular Respiration: Harvesting Chemical Energy
Chapter 9
Cellular Respiration:
Harvesting Chemical Energy
Main Objective is discovering how cells use the energy stored in food molecules to make ATP. Catabolic pathways do not directly move anything, they are linked to work by a chemical drive shaft: ATP.

2. Biology, 9th ed,Sylvia Mader
Chapter 08
Cellular Respiration
Cellular Respiration
Cellular respiration is a cellular process that breaks down nutrient molecules with the concomitant production of ATP
Consumes oxygen and produces carbon dioxide (CO2)
Cellular respiration is an aerobic process.
Usually involves the breakdown of glucose to CO2 and H2O
Energy is extracted from the glucose molecule:
Released step-wise
Allows ATP to be produced efficiently
Oxidation-reduction enzymes include NAD+ and FAD as coenzymes

3. Biology, 9th ed,Sylvia Mader
Chapter 08
Cellular Respiration
Cellular Respiration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Oxidation
C6H12O6 +
6O2
6CO2 +
6H2O +
energy
glucose
Reduction
Electrons are removed from substrates and received by oxygen, which combines with H+ to become water.
Glucose is oxidized and O2 is reduced

5. ATP
Remember that ATP is like a loaded spring. It has three negatively charged Phosphate groups attached and that the 3 P’s close together are unstable.
Cells must recycle the inorganic P that comes off ATP in order to regenerate its supply of ATP
Muscle cells recycle the ATP at a rate of 10 million molecules per second

6. Biology, 9th ed,Sylvia Mader
Chapter 08
Cellular Respiration
Cellular Respiration
NAD+ (nicotinamide adenine dinucleotide)
A coenzyme of oxidation-reduction. It can:
Oxidize a metabolite by accepting electrons
Reduce a metabolite by giving up electrons
Each NAD+ molecule is used over and over again
FAD (flavin adenine dinucleotide)
Also a coenzyme of oxidation-reduction
Sometimes used instead of NAD+
Accepts two electrons and two hydrogen ions (H+) to become FADH2

7. Why does the decomposition of Glucose lead to energy?
Transfer of Electrons!
Relocation of e- releases energy stored in food molecules and this energy is used to synthesize ATP
Activation energy of Glucose is high, much higher than body temperature. Enzymes help to lower activation energy.

8. Biology, 9th ed,Sylvia Mader
Chapter 08
Animation
Cellular Respiration
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10. Biology, 9th ed,Sylvia Mader
Chapter 08
Cellular Respiration
Cellular Respiration
Cellular respiration includes four phases:
Glycolysis is the breakdown of glucose into two molecules of pyruvate
Occurs in the cytoplasm
ATP is formed
Does not utilize oxygen
Preparatory (prep) reaction
Both pyruvates are oxidized and enter the mitochondria
Electron energy is stored in NADH
Two carbons are released as CO2 (one from each pyruvate)

11. Biology, 9th ed,Sylvia Mader
Chapter 08
Cellular Respiration
Cellular Respiration
Citric acid cycle
Occurs in the matrix of the mitochondrion and produces NADH and FADH2
In series of reactions, it releases 4 carbons as CO2
Turns twice per glucose molecule (once for each pyruvate)
Produces two immediate ATP molecules per glucose molecule
Electron transport chain (ETC)
Extracts energy from NADH & FADH2
Passes electrons from higher to lower energy states
Produces 32 or 34 molecules of ATP

12. Outside the Mitochondria: Glycolysis
Biology, 9th ed,Sylvia Mader
Chapter 08
Outside the Mitochondria: Glycolysis
Cellular Respiration
Glycolysis occurs in cytoplasm outside mitochondria
Energy Investment Step:
Two ATP are used to activate glucose
Glucose splits into two G3P molecules
Energy Harvesting Step:
Oxidation of G3P occurs by removal of electrons and hydrogen ions
Two electrons and one hydrogen ion are accepted by NAD+ resulting in two NADH
Four ATP are produced by substrate-level phosphorylation
Net gain of two ATP (4 ATP produced - 2 ATP consumed)
Both G3Ps converted to pyruvates

13. Outside the Mitochondria: Glycolysis
Biology, 9th ed,Sylvia Mader
Chapter 08
Outside the Mitochondria: Glycolysis
Cellular Respiration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Glycolysis
inputs
outputs
6C glucose
2 (3C)
pyruvate
2 NAD+
2 NADH
ATP
2 ADP 2
4 ADP P
ATP
total 4 2
ATP
net gain

14. Glycolysis

16. Biology, 9th ed,Sylvia Mader
Chapter 08
Animation
Cellular Respiration
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17. Biology, 9th ed,Sylvia Mader
Chapter 08
Animation
Cellular Respiration
D:\ImageLibrary1-17\09-CellularRespiration\09-09-Glycolysis.mov
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18. Outside the Mitochondria: Fermentation
Biology, 9th ed,Sylvia Mader
Chapter 08
Outside the Mitochondria: Fermentation
Cellular Respiration
Pyruvate is a pivotal metabolite in cellular respiration
If O2 is not available to the cell, fermentation, an anaerobic process, occurs in the cytoplasm.
During fermentation, glucose is incompletely metabolized to lactate, or to CO2 and alcohol (depending on the organism).
If O2 is available to the cell, pyruvate enters the mitochondria for aerobic respiration.

19. Outside the Mitochondria: Fermentation
Biology, 9th ed,Sylvia Mader
Chapter 08
Outside the Mitochondria: Fermentation
Cellular Respiration
Fermentation is an anaerobic process that reduces pyruvate to either lactate or alcohol and CO2
NADH transfers its electrons to pyruvate
Alcoholic fermentation, carried out by yeasts, produces carbon dioxide and ethyl alcohol
Used in the production of alcoholic spirits and breads.
Lactic acid fermentation, carried out by certain bacteria and fungi, produces lactic acid (lactate)
Used commercially in the production of cheese, yogurt, and sauerkraut.
Other bacteria produce chemicals anaerobically, including isopropanol, butyric acid, proprionic acid, and acetic acid.

20. Biology, 9th ed,Sylvia Mader
Fermentation
Chapter 08
Cellular Respiration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
glucose
– 2
ATP 2
ATP E1
2ADP 2 C C C P
G3P
2NAD; 2 P E2
2 NADH 2 P C C C P
BPG
4ADP E3
+ 4
ATP 4
ATP 2 C C C
pyruvate E4 or C C
2CO 2 2
ATP
(net gain) C C C C
2 lactate or
2 alcohol
Animals
Plants

21. Fermentation Helps Produce Numerous Food Products
Biology, 9th ed,Sylvia Mader
Chapter 08
Cellular Respiration
Fermentation Helps Produce Numerous Food Products
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© The McGraw Hill Companies, Inc./Bruce M. Johnson, photographer

22. Fermentation Helps Produce Numerous Food Products
Biology, 9th ed,Sylvia Mader
Chapter 08
Fermentation Helps Produce Numerous Food Products
Cellular Respiration

23. Fermentation Helps Produce Numerous Food Products
Biology, 9th ed,Sylvia Mader
Chapter 08
Fermentation Helps Produce Numerous Food Products
Cellular Respiration

24. Outside the Mitochondria: Fermentation
Biology, 9th ed,Sylvia Mader
Chapter 08
Outside the Mitochondria: Fermentation
Cellular Respiration
Advantages
Provides a quick burst of ATP energy for muscular activity.
Disadvantages
Lactate and alcohol are toxic to cells.
Lactate changes pH and causes muscles to fatigue.
Oxygen debt
Yeast die from the alcohol they produce by fermentation
Efficiency of Fermentation
Two ATP produced per glucose of molecule during fermentation is equivalent to 14.6 kcal.
Complete oxidation of glucose can yield 686 kcal.
Only 2 ATP per glucose are produced, compared to 36 or 38 ATP molecules per glucose produced by cellular respiration.

25. Outside the Mitochondria: Fermentation
Biology, 9th ed,Sylvia Mader
Chapter 08
Outside the Mitochondria: Fermentation
Cellular Respiration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fermentation
inputs
outputs
glucose
2 lactate or
2 alcohol and 2 CO2
ATP
2 ADP + 2 P 2
net gain

26. ½ Step between Glycolysis and Kreb’s
Carboxyl Group is broken off and expelled as CO2
A two Carbon fragment is left and oxidized into acetate. An enzyme transfers the extracted e- to NAD+ reducing it to NADH
CoEnzyme A will attach to acetate and make Acetyl CoA
This only happens if Oxygen is present

27. Figure Conversion of pyruvate to acetyl CoA, the junction between glycolysis and the Krebs cycle

28. Mitochondrion Structure and Function
Biology, 9th ed,Sylvia Mader
Mitochondrion Structure and Function
Chapter 08
Cellular Respiration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cristae: location
of the electron
transportchain
(ETC)
Matrix: location
of the prep
reaction and the
citric acid cycle
outer
membrane
inner
membrane
cristae
intermembrane
space
matrix
45,0003X
© Dr. Donald Fawcett and Dr. Porter/Visuals Unlimited

29. Inside the Mitochondria
Biology, 9th ed,Sylvia Mader
Chapter 08
Inside the Mitochondria
Cellular Respiration
Citric Acid Cycle
Also called the Krebs cycle
Occurs in the matrix of mitochondria
Begins with the addition of a two-carbon acetyl group (from acetyl-CoA) to a four-carbon molecule (oxaloacetate), forming a six-carbon molecule (citric acid)
NADH and FADH2 capture energy rich electrons
ATP is formed by substrate-level phosphorylation
Turns twice for one glucose molecule (once for each pyruvate)
Produces 4 CO2, 2 ATP, 6 NADH and 2 FADH2 per glucose molecule
D:\ImageLibrary1-17\09-CellularRespiration\09-12-KrebsCycle.mov

30. Citric Acid Cycle Cellular Respiration Biology, 9th ed,Sylvia Mader
Chapter 08
Slide #30
Cellular Respiration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
NADH e–
NADH e– e–
NADHand
FADH2 e– e– e– e–
Glycolysis
Preparatory reaction
Citric acid
cycle
Electron transport
chain and
chemiosmosis
glucose
pyruvate
Matrix
2 ATP
2 ADP
4 ADP
4 ATP total 2
ATP
1. The cycle begins when a
C2 acetyl group carried by
CoA combines with a C4
molecule to form citrate.
net
2ADP 2
ATP
32ADP
or 34 32
or 34
ATP
CoA
acetyl CoA C2
citrate C6
NAD
oxaloacetate C2
NADH
NADH
2. Twice over, substrates
are oxidized as NAD+ is
Reduced to NADH,
and CO2 is released.
5. Once again a substrate
is oxidized, and NAD+
is reduced to NADH.
Citric acid
cycle
NAD+
CO2
fumarate C4
ketoglutarate C5
NAD+
succinate C4
4. Again a substrate is
oxidized, but this time
FAD is reduced to FADH2
FAD
CO2
NADH
FADH
ATP
3. ATP is produced as an
energized phosphate is
transferred from a
substrate to ADP.

31. Figure 9.11 A closer look at the Krebs cycle (Layer 4)

32. h

33. Biology, 9th ed,Sylvia Mader
Chapter 08
Animation
Cellular Respiration
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at

34. Inside the Mitochondria
Biology, 9th ed,Sylvia Mader
Chapter 08
Inside the Mitochondria
Cellular Respiration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Citric acid cycle
inputs
outputs
4 CO2
2 (2c) acetyl groups 6
NADH
6 NAD+ 2
FADH2
2 FAD
2 ADP +2 P 2
ATP

35. Inside the Mitochondria
Biology, 9th ed,Sylvia Mader
Chapter 08
Inside the Mitochondria
Cellular Respiration
Electron Transport Chain (ETC)
Location:
Eukaryotes: cristae of the mitochondria
Aerobic prokaryotes: plasma membrane
Series of carrier molecules:
Pass energy-rich electrons successively from one to another
Complex arrays of protein and cytochrome
Cytochromes are proteins with heme groups with central iron atoms
The electron transport chain
Receives electrons from NADH & FADH2
Produces ATP by oxidative phosphorylation
Oxygen serves as the final electron acceptor
Oxygen combines with hydrogen ions to form water

36. Inside the Mitochondria
Biology, 9th ed,Sylvia Mader
Chapter 08
Inside the Mitochondria
Cellular Respiration
The fate of the hydrogens:
Hydrogens from NADH deliver enough energy to make 3 ATPs
Those from FADH2 have only enough for 2 ATPs
“Spent” hydrogens combine with oxygen
Recycling of coenzymes increases efficiency
Once NADH delivers hydrogens, it returns (as NAD+) to pick up more hydrogens
However, hydrogens must be combined with oxygen to make water
If O2 is not present, NADH cannot release H+
No longer recycled back to NAD+

37. Inside the Mitochondria
Biology, 9th ed,Sylvia Mader
Chapter 08
Inside the Mitochondria
Cellular Respiration
The electron transport chain complexes pump H+ from the matrix into the intermembrane space of the mitochondrion
H+ therefore becomes more concentrated in the intermembrane space, creating an electrochemical gradient.
ATP synthase allows H+ to flow down its gradient.
Flow of H+ drives the synthesis of ATP from ADP and inorganic phosphate by ATP synthase.
This process is called chemiosmosis
ATP production is linked to the establishment of the H+ gradient
ATP moves out of mitochondria and is used for cellular work
It can be broken down to ADP and inorganic phosphate
These molecules are returned to the mitochondria for more ATP production
D:\ImageLibrary1-17\09-CellularRespiration\09-15-ElectronTransport.mov 37

38. Organization and Function of the Electron Transport Chain
Biology, 9th ed,Sylvia Mader
Chapter 08
Organization and Function of the Electron Transport Chain
Cellular Respiration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
NADH e-
NADH e- e-
NADH and
FADH2 e- e- e- e-
Glycolysis
Preparatory reaction
Citric acid
cycle
Electron transport
chemiosmosis
chain and
glucose
pyruvate
2ATP
2ADP
4 ADP
4 ATP total 2
ATP
net
ADP
or 34
32 ADP
32 or 34
ATP H+
Electron transport chain
NADH-Q
reductase H+ H+ H+ H+ H+
cytochrome
reductase H+ H+ H+
cytochrome c
coenzyme Q H+
cytochrome
oxidase H+ e : H+ H+
low energy
electron
FADH2 :
high energy
electron
FAD + e H+ 2 H+ H+
NAD+ H+ 2 H+
NADH H+ H+ H+
H2O 1 O2
ATP
ADP H+ + P 2 H+ H+
Matrix H+
Intermembrane
space H+ H+ H+
ATP
synthase
complex H+ H+ H+ H+
ATP
channel
protein H+ H+
Chemiosmosis
ATP H+ H+

39. Figure 9.15 Chemiosmosis couples the electron transport chain to ATP synthesis

40. Figure 9.14 ATP synthase, a molecular mill

41. Review: Cellular Respiration
Glycolysis: ATP (substrate-level phosphorylation)
Kreb’s Cycle: ATP (substrate-level phosphorylation)
Electron transport & oxidative phosphorylation: NADH (glycolysis) = 6ATP NADH (acetyl CoA) = 6ATP NADH (Kreb’s) = 18 ATP
2 FADH2 (Kreb’s) = 4 ATP
38 TOTAL ATP/glucose

42. Biology, 9th ed,Sylvia Mader
Chapter 08
Animation
Cellular Respiration
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at

43. Biology, 9th ed,Sylvia Mader
Chapter 08
Animation
Cellular Respiration
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at