Chapter 9 Cellular Respiration. I.Catabolic Pathways Yield Energy A.Cellular Respiration 1.C 6 H 12...

Chapter 9

Cellular Respiration

I. Catabolic Pathways Yield Energy

A. Cellular Respiration1. C6H12O6 + 6O2 6CO2 + 6H2O

2. Exergonic

3. ATP production is the benefit for the cell

B. Redox Reactions: Transfer electrons from one reactant to another reactant

1. Oxidation: Substance loses electrons (Na)

2. Reduction: Substance gains electrons (Cl)

3. Electronegativity: An atoms ability to attract electrons to itself (Cl)

4. Energy is released when an electron changes location.

C. Redox Reactions when electrons are shared.

1. Some redox reactions change the degree to which electrons are shared.

2. Methane Example

CH4

H

H

HH CO O O O OC

H H

Methane(reducingagent)

Oxygen(oxidizingagent)

Carbon dioxide Water

+ 2O2 CO2 + Energy + 2 H2O

becomes oxidized

becomes reduced

Reactants Products

Figure 9.3

3. Cellular respiration is similar.a) C6H12O6 + 6O2 6CO2 + 6H2O

b) Hydrogens are transferred to Oxygen

c) More importantly, hydrogen’s electrons move away from it and closer to oxygen

d) Much energy is released in this motion

D. NAD+ and Energy harvest from e-

1. Hydrogen does not immediately join Oxygen to form water. (C6H12O6 + O2 CO2 H2O)

2. NAD+: (Nicotinamide adenine dinucleotide)a) Allows e- energy to be harvested slowly.

(a) Uncontrolled reaction

Fre

e en

ergy

, G

H2O

Explosiverelease of

heat and lightenergy

Figure 9.5 A

H2 + 1/2 O2

3. NAD+: (Nicotinamide adenine dinucleotide)a) Allows e- energy to be harvested slowly.

i. NAD+ strips 2 e-s from glucose

ii. Along with them come 2 hydrogens (NADH + H+)

iii. Very little energy is lost from the electrons here.

iv. The 2e- s can be passed to other molecules to release E. to make ATP

2H+

OH2O

ATP

ATP

ATP

E. The Stages of Cellular Respiration 1. Glycolysis

» Glucose (6C)Pyruvate(3C) » in Cytoplasm

2. Citric Acid Cycle» products of glycolysis broken down to CO2

» inside mitochondria

3. Electron Transport: (Oxidative Phosphorylation)

» High Energy Electrons from 1 and 2 passed down a chain of molecules to produce H2O.

» The energy released in the chain is used to make ATP via (oxidative phosphorylation)

F. Substrate-Level Phosphorylation: Adding a phosphate to ADP to make ATP1. phosphate from an organic molecule rather than

free floating.

Figure 9.7

Enzyme Enzyme

ATP

ADP

Product

SubstrateP

+

CH2O P

Glucose-6-phosphate

Glyceraldehyde-3-phosphate

II. GlycolysisC

Glucose

Hexokinase1

PA P P

PA P P

O

CH2O PC

Fructose-6-phosphate

Phosphoglucoisomerase 2

PO

CH2P CH2O O

Fructose-1,6-bisphosphate

Phosphofructokinase3

CP O

C=O

C PCH2 O

C=O

C

Aldolase4

Isomerase5

Glyceraldehyde-3-phosphate

PCH2 O

C=O

C

Dihydroxyacetone Phosphate

PCH2 O

C=O

C

Glyceraldehyde-3-phosphate

PCH2 O

C=O

C

P O

1,3-Bisphosphoglycerate

Triose phosphate dehydrogenase

6

PCH2 O

C=O

C

3-Phosphoglycerate

P

C

O

C=O

C

Phosphoenolpyruvate

C

C=O

C=O

Pyruvate

P

A P P

P

Phosphoglycerokinase7

P

A P P

P

C

O

C=O

C

2-Phosphoglycerate

Phosphoglyceromutase8

Enolase9

Pyruvate Kinase10

III. Citric Acid CycleA. Preparation

1. Pyruvate enters mitochondria

2. If oxygen is present cell resp. proceeds.

3. Acetyl CoA produced1. CO2 removed

2. Oxidation by NAD+

3. Coenzyme A attached to remaining two carbons.

4. Acetyl CoA enters the Citric Acid Cycle

Coenzyme AC

C=O

C=O

Pyruvate

O-

C

C=O

CoANAD+ NADH + H+

CO2

ATP

2 CO2

3 NAD+

3 NADH

+ 3 H+

ADP + P i

FAD

FADH2

Citricacidcycle

CoA

CoA

Acetyle CoA

NADH

+ 3 H+

CoA

CO2

Pyruvate(from glycolysis,2 molecules per glucose)

ATP ATP ATP

Glycolysis Citricacidcycle

Oxidativephosphorylation

Figure 9.11

C

C=O

CoA

Acetyl CoA

COO-

O=C

C

COO-

Oxaloacetate

COO-

HO-C

C

COO-

C

COO-

Citrate

COO-

C COO-

C

COO-

HO-C

Isocitrate

COO-

C

C

COO-

O=C

α-Ketogluterate

C

C

COO-

O=C

CoASuccinyl CoAC

C

COO-

COO-

Succinate

C

C

COO-

COO-

Fumarate

C

HO-C

COO-

COO-

Malate

COO-

O=C

C

COO-

Oxaloacetate

H2O

H2O

CO2

NAD+

NADH + H+

CO2

NAD+NADH+ H+

CoA

CoA

AP P

P

PAP P

FAD

FADH2H2O

NAD+

NADH+ H+

Acetyl CoA

NADH

Oxaloacetate

CitrateMalate

Fumarate

Succinate

SuccinylCoA

-Ketoglutarate

Isocitrate

Citricacidcycle

S CoA

CoA SH

NADH

NADH

FADH2

FAD

GTP GDP

NAD+

ADP

P i

NAD+

CO2

CO2

CoA SH

CoA SH

CoAS

H2O

+ H+

+ H+ H2O

C

CH3

O

O C COO–

CH2

COO–

COO–

CH2

HO C COO–

CH2

COO–

COO–

COO–

CH2

HC COO–

HO CH

COO–

CH

CH2

COO–

HO

COO–

CH

HC

COO–

COO–

CH2

CH2

COO–

COO–

CH2

CH2

C O

COO–

CH2

CH2

C O

COO–

1

2

3

4

5

6

7

8NAD+

+ H+

ATP

Figure 9.12

Results of CAC (one turn)

ATP = NADH = FADH2 =CO2 =

131

2

C

C=O

CoA

Acetyl CoA

COO-

O=C

C

COO-

Oxaloacetate

COO-

HO-C

C

COO-

C

COO-

Citrate

COO-

C COO-

C

COO-

HO-C

Isocitrate

COO-

C

C

COO-

O=C

α-Ketogluterate

C

C

COO-

O=C

CoASuccinyl CoAC

C

COO-

COO-

Succinate

C

C

COO-

COO-

Fumarate

C

HO-C

COO-

COO-

Malate

CoA

CoA

CoA

H2O

H2O

CO2

CO2 NAD+

NAD+

NAD+

NADH+ H+

NADH+ H+

NADH+ H+

FADFADH2 PAP P

P

AP P

IV. Electron Transport, Oxidative Phosphorylation and Chemiosmosis

A. Structure of Mitochondria Matrix: Juice. Site

of Citric acid cycle.

A. Cristae: Folds in the inner memebrane. Site of electron

transport.

B. Intermembrane space:

B. Electron Transport Overview: The following animation and diagram are an overview of the process. Definitions will follow.

-Oxidative Phosphorilation: ATP production using energy derived from redox reactions.

NADH

Outer Membrane

H+

Inner Membrane

Intermembrane Space

Matrix

H+

H+

FADH2FAD

OH2O

Complex 1

Complex 2

Complex

3

Complex 4

NAD+

ADP

PATP

ATP Synthase

ubiquinone

NADH

Outer Membrane

H+

Inner Membrane

Intermembrane Space

MatrixH+

H+

O

H2O

Complex 1

Complex 2

Complex 3

Complex 4

NAD+

ADP + P

ATP

2e -

2e-

2e-

2e- 2e -

H+

H+

H+

H+H+

H+

H+

H+ H+

ATP Synthase

ubiquinone

FAD

Outer Membrane

H+

Inner Membrane

Intermembrane Space

Matrix

H+

O

H2O

Complex 1

Complex 2

Complex 3

Complex 4

FADH2

ADP + P

ATP

2e-

2e-

2e- 2e -

H+

H+

H+H+

H+

H+

H+ H+

ATP Synthase2e

-

C. Chemiosmosis:1. The process of electron transport makes no

ATP directly.

2. Electron transport creates a H+ gradient.a. Results in high H+ amounts in the intermembrane

space.

b. This is like water build up behind a dam. It has a lot of potential energy.

c. Proton-motive force: The name given to the gradient. i. The force tries to push the protons back across the

membrane to reach equilibrium.

d. Chemiosmosis: Using energy stored in the H+ gradient across a membrane to synthesize ATP.

D. ATP Synthase: The enzyme that makes the ATP

1. ATP synthase is the only place protons can go back through the membrane

INTERMEMBRANE SPACE

H+

H+

H+

H+

H+

H+ H+

H+

P i

+ADP

ATP

A rotor within the membrane spins clockwise whenH+ flows past it down the H+

gradient.

A stator anchoredin the membraneholds the knobstationary.

A rod (for “stalk”)extending into the knob alsospins, activatingcatalytic sites inthe knob.

Three catalytic sites in the stationary knobjoin inorganic Phosphate to ADPto make ATP.

MITOCHONDRIAL MATRIXFigure 9.14

E. Energy Totals for Cellular Respiration1. ATP Formed

– Glycolysis = 2

– Pyruvate Oxydation = 0

– CAC = 2

2. NADH Generated

– Glycolysis = 2

– Pyruvate OXydation = 2

– CAC = 6

– ATP/ NADH = 3

– Total ATP from all NADH = 30

3. FADH2 Generated

– Glycolysis = 0

– Pyruvate Oxydation = 0

– CAC= 2

– ATP generated per FADH2 = 2

– Total ATP from FADH2 = 4

• Total ATP from catabolism of one glucose = 38 sometimes 36

V. Fermentation: Production of ATP from glucose when no oxygen is present (Anaerobic)

A. General Rules:1. Cellular respiration can’t happen w/o oxygen

2. Fermentation allows us to make ATP anyway.

3. Glycolysis makes 2 ATP by subtrate level phosphorilation. a. If done rapidly this could be enough to get by

b. The limiting factor is the amount of available NAD+ available.

4. Fermentation allows glycolysis to continue by oxidizing the NADH for reuse.

B. Types: 1. Alcohol Fermentation: Pyruvate is converted to

ethanol.– Often used by bacteria and yeast

– Step 1: Pyruvate releases 2CO2 Acetaldehyde

– Step 2: Acetaldehyde oxidizes NADH ethanol and NAD+

2 ADP + 2 P1 2 ATP

GlycolysisGlucose

2 NAD+ 2 NADH

2 Pyruvate

2 Acetaldehyde 2 Ethanol

(a) Alcohol fermentation

H

H OH

CH3

C

O –

OC

C O

CH3

H

C O

CH3

CO22

2 ADP + 2 P1 2 ATP

GlycolysisGlucose

2 NAD+ 2 NADH

2 Pyruvate

2 Acetaldehyde 2 Ethanol

(a) Alcohol fermentation

2 ADP + 2 P1 2 ATP

GlycolysisGlucose

2 NAD+ 2 NADH

2 Lactate

(b) Lactic acid fermentation

H

H OH

CH3

C

O –

OC

C O

CH3

H

C O

CH3

O–

C O

C O

CH3O

C O

C OHH

CH3

CO22

Figure 9.17

2. Lactic Acid Fermentation1. Happens in human muscles as well as bacteria that

make cheese.

2. One Step: Pyruvate oxidizes NADH NAD+ + Lactic Acid.

c. Comparing Fermentation and Cellular Respiration

Cellular Respiration1.Aerobic2.38 ATP produced3.NADH oxidized to produce H20

Fermentation1.Anaerobic2.2 ATP produced3.NADH oxidized to make ethanol or lactate