1. Cellular Respiration Sylvia S. Mader BIOLOGY Chapter 8: pp. 133-149
10th Edition
Chapter 8: pp
Cellular Respiration
Sylvia S. Mader
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Insert figure 8.2 here
NADH e–
NADH e– e– e–
Cytoplasm
NADH and e– F
ADH 2
Mitochondrion e– e–
Glycolysis
Preparatory reaction
cycle
Citric acid
Electron transport
chain and
chemiosmosis
glucose
pyruvate
2 ADP
2 ADP
4 ADP
4 ATP total 2
ATP
net gain
2 ADP 2
ATP
32 ADP
or 34 32
or 34
ATP 1
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2. Connection between Photosynthesis and Respiration
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3. Fermentation = anaerobic Cellular respiration = aerobic
STAGES OF CELLULAR RESPIRATION AND FERMENTATION
Fermentation = anaerobic Cellular respiration = aerobic
Cellular respiration oxidizes sugar and produces ATP in 3-4 main stages: Glycolysis, Prep (Transition) Stage, Kreb’s (Citric Acid) Cycle, ETC
Fermentation oxidizes sugar and does not produce ATP, but yields a constant supply of NAD+ (an electron carrier)
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4. Glucose Breakdown: Summary Reaction
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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 4

5. NAD+ and FAD NAD+ (nicotinamide adenine dinucleotide)
Called a coenzyme of oxidation-reduction. It can:
Oxidize a metabolite by accepting electrons
Reduce a metabolite by giving up electrons
Each NAD+ molecule 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 5

6. Cellular Respiration 6 O f r o m a i r H2O O2 and glucose enter cells,
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O 2 f r o m a i r
H2O
O2 and glucose enter cells,
which release H2O and CO2.
CO2 g l u c o s e f r o m
intermembrane
space
cristae
Mitochondria use
energy from
glucose to form ATP
from ADP P .
ADP + P
ATP
© E. & P. Bauer/zefa/Corbis; (Bread, wine, cheese, p. 139): © The McGraw Hill Companies, Inc./John Thoeming, photographer; (Yogurt, p. 139): © The McGraw Hill Companies, Inc./Bruce M. Johnson, photographer 6

7. ATP
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8. Phases of Cellular Respiration
Cellular respiration includes four phases:
Glycolysis is the breakdown of glucose into two molecules of pyruvate
Occurs in cytoplasm
ATP is formed
Does not utilize oxygen
Transition (preparatory) reaction
Both pyruvates are oxidized and enter mitochondria
Electron energy is stored in NADH
Two carbons are released as CO2 (one from each pyruvate) 7

9. Phases of Cellular Respiration
Citric acid cycle
Occurs in the matrix of the mitochondrion and produces NADH and FADH2
In series of reaction releases 4 carbons as CO2
Turns twice (once for each pyruvate)
Produces two immediate ATP molecules per glucose molecule
Electron transport chain
Extracts energy from NADH & FADH2
Passes electrons from higher to lower energy states
Produces 32 molecules of ATP 8

10. Glucose Breakdown: Overview of 4 Phases
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NADH
NADH e– e– e–
NADH and
FADH2
Cytoplasm e–
Mitochondrion e– e–
Glycolysis
Electron transport
chain and
chemiosmosis
Preparatory reaction
Citric acid
cycle
glucose
pyruvate
2 ATP
2 ATP
4 ADP
4 ATP total 2
ATP
net gain 2 AD P 2
ATP
32 ADP
or 34 32
or 34
ATP 9

11. Glucose Breakdown: Glycolysis
Occurs in cytoplasm outside mitochondria
Energy Investment Steps:
Two ATP are used to activate glucose
Glucose splits into two G3P molecules
Energy Harvesting Steps:
Oxidation of G3P occurs by removal of electrons and hydrogen ions
Two electrons and one hydrogen ion are accepted by NAD+ resulting two NADH
Four ATP produced by phosphorylation
Net gain of two ATP
Both G3Ps converted to pyruvates 10

12. First phase in aerobic respiration is GLYCOLYSIS…
First phase in aerobic respiration is GLYCOLYSIS….no oxygen involved in this phase
Glycolsis
Glucose
Pyruvate
ATP
Substrate-level
phosphorylation
Mitochondrion
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13. PREPARATORY PHASE (energy investment)
Steps – A fuel molecule is energized, using ATP.
Glucose 1 3
Details of glycolysis Do we need to know that??!!
Step 1
Glucose-6-phosphate 2
Fructose-6-phosphate 3
Fructose-1,6-diphosphate
Step A six-carbon intermediate splits into two three-carbon intermediates. 4 4
Glyceraldehyde-3-phosphate (G3P)
ENERGY PAYOFF PHASE 5
Step A redox reaction generates NADH. 5
1,3-Diphosphoglyceric acid (2 molecules) 6
Steps – ATP and pyruvic acid are produced.
3-Phosphoglyceric acid (2 molecules) 6 9 7
2-Phosphoglyceric acid (2 molecules) 8
2-Phosphoglyceric acid (2 molecules) 9
Pyruvic acid
Figure 6.9B
(2 molecules per glucose molecule)
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14. GLYCOLYSIS BASICS http://highered. mcgraw-hill
Glucose
Pyruvic acid
Figure 6.9A
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15. Glycolysis: Inputs and Outputs
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Glycolysis
inputs
outputs
glucose
2 pyruvate
2 NAD+
2 NADH 2
ATP
2 ADP
4 ADP + 4 P
4 ATP total 2
ATP
net gain 11

16. Pyruvate 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 mitochondria by aerobic process. 16

17. Fermentation
An anaerobic process that reduces pyruvate to either lactate or alcohol and CO2
NADH passes 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. 17

18. Fermentation is an anaerobic alternative to aerobic respiration
Under anaerobic conditions, many kinds of cells can use glycolysis alone to produce small amounts of ATP
But a cell must have a way of replenishing NAD+
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19. ALCOHOLIC FERMENTATION
In alcoholic fermentation, pyruvic acid is converted to CO2 and ethanol
This recycles NAD+ to keep glycolysis working
released
GLYCOLYSIS
2 Pyruvic acid
2 Ethanol
Glucose
Figure 6.15A
Figure 6.15C
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20. LACTIC ACID FERMENTATION
In lactic acid fermentation, pyruvic acid is converted to lactic acid
As in alcoholic fermentation, NAD+ is recycled
Lactic acid fermentation is used to make cheese and yogurt
GLYCOLYSIS
2 Pyruvic acid
2 Lactic acid
Glucose
Figure 6.15B
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21. Efficiency of Fermentation
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Fermentation
inputs
outputs
glucose
2 lactate or
2 alcohol and 2 CO2
2 ADP + 2 P 2
ATP
net gain 25

22. Acetyl CoA (acetyl coenzyme A)
Pyruvic acid is chemically groomed for the Krebs cycle in the Transition or Prep Stage
Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle
Pyruvic acid
Acetyl CoA (acetyl coenzyme A)
CO2c
Figure 6.10
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23. Aerobic Respiration Continues in the Mitochondria
ATP
Substrate-level
phosphorylation
Mitochondrion
Glycolsis
Glucose
Pyruvate
Citric acid cycle
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24. Alpha-ketoglutaric acid
Details of the Kreb’s Cycle…….
Do we need to know all that????
Answer: Yes and No
2 carbons enter cycle
Oxaloacetic acid 1
Citric acid
CO2 leaves cycle 5
KREBS CYCLE 2
Malic acid 4
Alpha-ketoglutaric acid 3
CO2 leaves cycle
Succinic acid
Step
Acetyl CoA stokes the furnace
Steps and
NADH, ATP, and CO2 are generated during redox reactions.
Steps and
Redox reactions generate FADH2 and NADH. 1 2 3 4 5
Figure 6.11B
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25. Let’s look at a simplified version of the Kreb’s Cycle first…..
The Krebs cycle completes the oxidation of glucose, generating many NADH and FADH2 molecules
Acetyl CoA
The Krebs cycle is a series of reactions in which enzymes strip away electrons and H+ from each acetyl group
What are the products of the Kreb’s cycle? 2
KREBS CYCLE
CO2
Figure 6.11A
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26. KREB’S CYCLE aka Citric Acid Cycle……. times 2…. WHY. http://highered
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27. Oxidative Phosphorylation = ETC plus Chemiosmosis
Electrons
carried
via NADH
Glycolsis
Glucose
Pyruvate
ATP
Substrate-level
phosphorylation
Electrons carried
via NADH and
FADH2
Citric acid cycle
Oxidative phosphorylation: electron transport and chemiosmosis
Oxidative
Mitochondrion
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28. Chemiosmosis powers most ATP production
The electrons from NADH and FADH2 travel down the electron transport chain (slowly losing energy). They will be grabbed by oxygen
Energy released by the electrons is used to pump H+ into the space between the mitochondrial membranes
In chemiosmosis, the H+ ions diffuse back through the inner membrane through ATP synthase complexes, which capture the energy to make ATP
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29. Electron transport chain
Therefore, the two mechanisms that generate ATP are ETC and Chemiosmosis
Cells use the energy released by “falling” electrons to pump H+ ions across a membrane
The energy of the gradient is harnessed to make ATP by the process of chemiosmosis
High H+ concentration
ATP synthase uses graient energy to make ATP
Membrane
Electron transport chain
ATP synthase
Energy from
Low H+ concentration
Figure 6.7A
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30. Overview of Cellular Respiration (Aerobic)6
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31. INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS
Cells use many kinds of organic molecules as fuel for cellular respiration
Polysaccharides can be hydrolyzed to monosaccharides and then converted to glucose for glycolysis
Proteins can be digested to amino acids, which are chemically altered and then used in the Krebs cycle
Fats are broken up and fed into glycolysis and the Krebs cycle
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32. ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS
Pathways of molecular breakdown
Food, such as peanuts
Polyscaccharides
Fats
Proteins
Sugars
Glycerol
Fatty acids
Amino acids
Amino groups
Pyruvic acid
ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS
Glucose
G3P
Acetyl CoA
KREBS CYCLE
GLYCOLYSIS
Figure 6.16
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33. The fuel for respiration ultimately comes from photosynthesis
All organisms have the ability to harvest energy from organic molecules
Plants, but not animals, can also make these molecules from inorganic sources by the process of photosynthesis (Chapter 7)
Figure 6.18
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