1. CELLULAR RESPIRATION
Chapter 6

2. Sunlight energy Photosynthesis in chloroplasts + + (for cellular work)
ECOSYSTEM
Photosynthesis
in chloroplasts
CO2
Glucose + +
H2O O2
Cellular respiration
in mitochondria
Figure 6.1 The connection between photosynthesis and cellular respiration.
ATP
(for cellular work)
Heat energy

3. Cellular Respiration Banks Energy in ATP Molecules
C6H12O6 O2 6
CO2
+ 6
H2O +
+ 6
ATPs
Carbon
dioxide
Glucose
Oxygen
Water
Energy
Cellular respiration transfers energy from the bonds of glucose storing it in ATP (~38 ATP/glucose are produced)
When the bonds of glucose are broken, electrons are stripped from it and ultimately transferred to oxygen
Figure 6.3 Summary equation for cellular respiration: C6H12O6 + 6 O2 6 CO2 + H2O + energy

4. Cells Tap Energy From Electrons “falling” From Organic Fuels to Oxygen
C6H12O6
CO2 +
ATPs
+ 6 O2 6 + 6
H2O
Carbon
dioxide
Glucose
Oxygen
Water
Energy
Oxygen is electronegative, thus pulling these e- towards it
As electrons move from glucose to oxygen, energy is released in small amounts, stored in a gradient that is used to synthesize ATP
Other foods (organic molecules) can be used as a source of energy as well

5. Cellular Respiration is a Redox Process, As is Photosynthesis
Loss of hydrogen atoms
(oxidation)
C6H12O O2
6 CO H2O Energy
Glucose
(ATP)
Gain of hydrogen atoms
(reduction)
Figure 6.5A Rearrangement of hydrogen atoms (with their electrons) in the redox reactions of cellular respiration.

6. Enzymes are Necessary to Oxidize Glucose and Other Foods
The enzyme that removes hydrogens from organic molecule is called dehydrogenase
Oxidation
Dehydrogenase
Figure 6.5B A pair of redox reactions, occurring simultaneously.
Reduction + H+
NAD+
+ 2 H
NADH
(carries
2 electrons)
2 H e–

7. Cells Tap Energy From Electrons “falling” from Organic Fuels to Oxygen
Dehydrogenase requires NAD+
(a coenzyme) to carry e- becoming NADH when it accepts e-
A related coenzyme, FAD functions like NAD+ (becoming FADH2 )
NADH and FADH2 “carry” e- originating from glucose over to the proteins embedded in the cristae of the mitochondria called the electron transport chain (ETC )
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8. NADH ATP NAD+ + 2e– Controlled release of H+ energy for synthesis
of ATP H+
Electron transport
chain
Figure 6.5C In cellular respiration, electrons fall down an energy staircase and finally reduce O2.
2e– H+ 1  2 O2
H2O

9. Breathing and cellular respiration are closely related
Breathing Supplies Oxygen to Our Cells For Use in Cellular Respiration and Removes Carbon Dioxide
Breathing and cellular respiration are closely related
Breathing is necessary for the exchange of CO2 produced during cellular respiration for atmospheric O2

10. Muscle cells carrying out
Breathing O2
CO2
Lungs
CO2 O2
Bloodstream
Figure 6.2 The connection between breathing and cellular respiration.
Muscle cells carrying out
Cellular Respiration
Glucose + O2
CO2 + H2O + ATP

11. STAGES OF CELLULAR RESPIRATION

12. Cellular Respiration Occurs in Three Main Stages
Stage 1: Glycolysis
Location: cytoplasm
Purpose: to begin the breakdown of glucose
What happens: A single molecule of glucose is enzymatically cut in half through a series of steps producing two molecules of pyruvate
Redox reactions produce NADH
Substrate-level phosphorylation produces ATP
Products/glucose : 2 pyruvate, 2 NADH, 2 ATP
The term glycolysis means “splitting of sugar.”

13. Figure 6.7C Details of glycolysis.
ENERGY INVESTMENT
PHASE
Glucose
ATP
Steps – A fuel molecule is energized,
using ATP. 1 3
Step 1
ADP P
Glucose-6-phosphate 2 P
Fructose-6-phosphate
ATP 3
ADP P P
Step A six-carbon intermediate splits
Into two three-carbon intermediates.
Fructose-1,6-bisphosphate 4 4 P P
Glyceraldehyde-3-phosphate
(G3P)
Step A redox reaction
generates NADH. 5
NAD+ 5
NAD+ 5
ENERGY PAYOFF PHASE
NADH P
NADH P
+ H+
+ H+ P P P P
1,3-Bisphosphoglycerate
ADP
ADP 6 6
ATP
ATP
Figure 6.7C Details of glycolysis. P P
3-Phosphoglycerate 7 7
Steps – ATP and pyruvate
are produced. 6 9 P P
2-Phosphoglycerate 8 8
H2O
H2O P P
Phosphoenolpyruvate
(PEP)
ADP
ADP 9 9
ATP
ATP
Pyruvate

14. Substrate-level Phosphorylation
Substrate-level phosphorylation is the enzymatic transfer of a phosphate group from a substrate molecule to ADP, forming ATP
Enzyme
Enzyme + P
ADP
Figure 6.7B Substrate-level phosphorylation: transfer of a phosphate group P from a substrate to ADP, producing ATP.
ATP P P
Substrate
Product

15. Pyruvate is Chemically Groomed for The Kreb’s Cycle
Grooming Step
Location: mitochondrial matrix
Purpose: to prepare pyruvate for entry into the Kreb’s cycle
What Happens: Occurs in three steps
1. The removal of a carboxyl group from pyruvate (first release
of CO2)
2. Oxidization of the remaining 2-carbon compound forming
acetate
3. Binding of Coenzyme A to the 2-carbon acetate
forming acetyl coenzyme A
Products/glucose: 2CO2 , 2 NADH, 2 Acetyl CoA

16. Pyruvate is Chemically Groomed for The Kreb’s Cycle
NAD+
NADH
 H+ 2
CoA
Pyruvate 1
Acetyl coenzyme A 3
CO2
Figure 6.8 The conversion of pyruvate to acetyl CoA.
Coenzyme A

17. Cellular Respiration Occurs in Three Main Stages
Stage 2: The Kreb’s Cycle (Citric Acid Cycle)
Location: mitochondrial matrix
Purpose: to complete the oxidation of glucose into CO2 and to form more electron carriers
What Happens: A 2-C acetate combines with 4-C oxaloacetate forming 6-C citrate.
Redox reactions produce NADH and FADH2
Substrate-level phosphorylation produces ATP
4-C Oxaloacetate is regenerated to bind acetate and begin cycle again
Products/glucose : 4 CO2, 6 NADH, 2 FADH2 , 2 ATP,

18. CITRIC ACID CYCLE Acetyl CoA 2 carbons enter cycle Oxaloacetate1
Citrate
NADH
+ H+
NAD+ 5
NAD+
NADH
+ H+ 2
CITRIC ACID CYCLE
Malate
CO2
leaves cycle
ADP  P
FADH2 4
ATP
Alpha-ketoglutarate
Figure 6.9B Details of the citric acid cycle.
FAD 3
CO2
leaves cycle
Succinate
NAD+
NADH
+ H+
Step
Acetyl CoA stokes the furnace. 1
Steps –
NADH, ATP, and CO2 are generated
during redox reactions. 2 3
Steps –
Redox reactions generate FADH2
and NADH. 4 5

19. Cellular Respiration Occurs in Three Main Stages
Stage 3: Oxidative phosphorylation (along the ETC)
Location: cristae of mitochondria
Purpose: generate a proton gradient to help form ATP
What Happens: NADH & FADH2 ,supply the electrons they are carying to the ETC. As e- are transferred from protein to protein, H+ are concentrated in the intermembrane space
The potential energy of this proton gradient is used to make ATP by chemiosmosis
The concentration gradient drives H+ through ATP synthases producing ATP
The ETC + chemiosmosis = oxidative phosphorylation
Products/glucose: ATP and H2O

20. Oxidative Phosphorylation
Protein
complex
of electron
carriers H+ H+
Electron
carrier H+ H+
ATP
synthase
Intermembrane
space
Inner
mitochondrial
membrane
FADH2
FAD
Electron
flow
NADH
NAD+ 2  1 O2
+ 2 H+ H+
Mitochondrial
matrix H+
Figure 6.10 Oxidative phosphorylation, using electron transport and chemiosmosis in the mitochondrion.
ADP + P H+
ATP
H2O H+
Electron Transport Chain
Chemiosmosis
OXIDATIVE PHOSPHORYLATION

21. OVERVIEW OF AEROBIC RESPIRATION
Electron shuttle
across membrane
Cytoplasm
Mitochondrion 2
NADH 2
NADH
(or 2 FADH2) 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 34 ATP
Figure 6.12 An estimated tally of the ATP produced by substrate-level and oxidative phosphorylation in cellular respiration.
by substrate-level
phosphorylation
by substrate-level
phosphorylation
by oxidative phosphorylation
About
38 ATP
Maximum per glucose:

22. Overview of Cellular Respiration

23. Fermentation Enables Cells to Produce ATP Without Oxygen
Fermentation is an anaerobic energy-generating process
Location: cytoplasm
Purpose: to produce ATP in the absence of oxygen
What Happens?: Glycolysis, and regeneration of NAD+
Pyruvate accepts electrons generated by redox reactions in glycolysis
Your muscle cells and certain bacteria can oxidize NADH through lactic acid fermentation
Copyright © 2009 Pearson Education, Inc.

24. Lactic Acid Fermentation Steps to regenerate NAD+
Glucose 2
NAD+
2 ADP  2 P
GLYCOLYSIS
Glycolysis 2
ATP 2
NADH
Lactic Acid Fermentation
2 Pyruvate 2
NADH
Steps to regenerate NAD+
Figure 6.13A Lactic acid fermentation oxidizes NADH to NAD+ and produces lactate. 2
NAD+
2 Lactate
Lactic acid fermentation

25. Fermentation Enables Cells to Produce ATP Without Oxygen
The baking and winemaking industry have used alcohol fermentation for thousands of years
Occurs in yeast cells (single-celled fungi)
Yeast convert pyruvate to CO2 and ethanol while oxidizing NADH back to NAD+

26. Steps to regenerate NAD+ with a release of CO2
Glucose
2 ADP 2
NAD+  2 P
GLYCOLYSIS
Glycolysis 2
ATP 2
NADH
Alcohol Fermentation
2 Pyruvate 2
NADH 2
CO2
Steps to regenerate NAD+ with a release of CO2
released 2
NAD+
2 Ethanol
Alcohol fermentation

27. INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS

28. Cells Use Many Kinds of Organic Molecules as Fuel for Cellular Respiration
Although glucose is considered the primary source of sugar for respiration and fermentation, three molecules can serve as substrates for generating ATP
Carbohydrates (disaccharides)
Proteins (after conversion to amino acids)
Fats

29. Food, such as peanuts Carbohydrates Fats Proteins Sugars Glycerol
Fatty acids
Amino acids
Amino
groups
Figure 6.15 Pathways that break down various food molecules.
OXIDATIVE
PHOSPHORYLATION
(Electron Transport
and Chemiosmosis)
CITRIC
ACID
CYCLE
Acetyl
CoA
Glucose
G3P
Pyruvate
GLYCOLYSIS
ATP

30. ATP needed to drive biosynthesis
GLUCOSE SYNTHESIS
CITRIC
ACID
CYCLE
Acetyl
CoA
Pyruvate
G3P
Glucose
Amino
groups
Amino acids
Fatty acids
Glycerol
Sugars
Proteins
Fats
Carbohydrates
Figure 6.16 Biosynthesis of large organic molecules from intermediates of cellular respiration.
Cells, tissues, organisms

31. Cellular respiration ATP (a) (b) (d) (c) (f) (e) generates
has three stages
oxidizes
uses
ATP
(a)
produce
some
C6H12O6
(b)
(d)
produces
many
energy for
to pull
electrons down to
(c)
(f)
by process called
uses
H+ diffuse
through
ATP synthase
(e)
uses
pumps H+ to create