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Cellular Respiration How we harvest energy from food

Today�s topics •  Oxidation and Reduction •  Glycolysis

–  glucose à pyruvate, ATP, NADH

–  in cytoplasm •  Mitochondria

–  Structure and function

•  Citric Acid cycle (if time)

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Atoms bonded in High Potential Energy Configuration

Atoms bonded in Low Potential Energy Configuration

Chemical Products have a lower Potential Energy than Reactants

Energy is Released

If one thing gets oxidized, another becomes reduced

Transfer of electrons from A to B

Reactants

becomes oxidized

Methane

Products

Energy

becomes reduced

Oxygen Carbon dioxide Water

Sometimes an electron Is only partially lost or gained

Change in the degree of electron sharing in covalent bonds

Oxidation, Reduction, and Energy

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•  Direct ATP production –  �Substrate Level Phosphorylation�

•  Electron Carriers -  NAD, NADP, FAD

–  Can �cash in� reduced carriers for ATP –  �Oxidative Phosphorylation�

How is energy harvested upon oxidation?

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ATP

Adenine

3 phosphate groups Ribose

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Electron Carriers

•  NAD+ nicotinamide adenine dinucleotide NAD+ + H+ + 2e- -> NADH

•  NADP+ nicotinamide adenine dinucleotide phosphate NADP+ + H+ + 2e- -> NADPH

•  FAD flavin adenine dinucleotide FAD + 2H+ + 2e- -> FADH2

NAD+/NADH Is an Electron Carrier

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Many Small

Controlled reactions

15 gallons Of gasoline

Your cells harvest energy from glucose in small steps

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Amino acids

Sugars Glycerol Fatty acids

Glycolysis Glucose

Glyceraldehyde-3- P

Pyruvate

Acetyl CoA

NH3

Citric acid

cycle

Oxidative phosphorylation

Fats Proteins Carbohydrates

Catabolic Pathways

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General Catabolic Pathway •  Step down the oxidation series of carbon in a series of small Steps

Some activation step Oxidation step, with energy harvest

Reorganization step Another oxidation step, another harvest

Another reorganization etc. etc.

yield product of pathway

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Amino acids

Sugars Glycerol Fatty acids

Glycolysis

Glucose

Glyceraldehyde-3- P

Pyruvate

Acetyl CoA

NH3

Citric acid

cycle

Oxidative phosphorylation

Fats Proteins Carbohydrates

Figure 9.19

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Glucose

(Two) 3 carbon acids

oxidized to pyruvate

Glycolysis:

6 carbon sugar Harvest

ATP and NADH

In Cytoplasm

On Inner Mitochondrial membrane

In Mitochondrial Matrix

Steps in the oxidation of glucose

For each process: What goes in? What comes out? Where does it happen? Keep track of the carbon atoms. Keep track of the energy molecules.

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Glycolysis Summary

Energy investment phase

Energy harvest phase

This is the amount of detail you should know 18 Dihydroxyacetone phosphate

Glyceraldehyde- 3-phosphate

H H

H

H H

OH OH

HO HO

CH2OH H H

H

H O H

OH HO

OH

P

CH2O P

H

O H

HO

HO

H HO

CH2OH

P O CH2 O CH2 O P

HO H HO

H OH

O P CH2 C O

CH2OH

H C CHOH

CH2

O

O P

ATP

ADP Hexokinase

Glucose

Glucose-6-phosphate

Fructose-6-phosphate

ATP

ADP

Phosphoglucoisomerase

Phosphofructokinase

Fructose- 1, 6-bisphosphate

Aldolase

Isomerase

1

2

3

4

5

CH2OH

Figure 9.9 A

2 of these

Glycolysis- the details Energy InvestmentStage

Add P (from ATP) Rearrange

Add P (from ATP)

Split into two 3 carbon units

Rearrange

Do Not Memorize! Just notice the sequential changes

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NADH + 2 H+

P i

2 P C

CHOH

O

P

O

CH2 O

2 O–

1, 3-Bisphosphoglycerate

ATP

CH2 O P

2

C

CHOH

3-Phosphoglycerate

O–

C

C

CH2OH

H O P

2-Phosphoglycerate

2 H2O

2 O–

Enolase

C

C

O

P O

CH2 Phosphoenolpyruvate

ATP O–

C

C

O

O

CH3

2

6

8

7

9

10

O

Figure 9.8 B

Pyruvate x2

2 X Glyceraldehyde-3-P

Glycolysis Energy payoff this pathway happens twice for each glucose

Oxidize aldehyde to acid add another phosphate

Harvest NADH

Make ATP by Substrate Level Phosphorylation

Rearrange

Oxidize alcohol to ketone

Make ATP by Substrate Level Phosphorylation

O

Do Not Memorize! Just notice the sequential changes

Do Not Memorize!

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Substrate-level Phosphorylation

Figure 9.6-3

Electrons carried

via NADH

Electrons carried via NADH and

FADH2

Citric acid cycle

Pyruvate oxidation

Acetyl CoA

Glycolysis

Glucose Pyruvate

Oxidative phosphorylation: electron transport

and chemiosmosis

CYTOSOL MITOCHONDRION

ATP ATP ATP

Substrate-level phosphorylation

Substrate-level phosphorylation

Oxidative phosphorylation

What happens to the products of glycolysis?

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Matrix

Inner Membrane

Intermembrane Space

Outer Membrane

Mitochondrion

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Amino acids

Sugars Glycerol Fatty acids

Glycolysis

Glucose

Glyceraldehyde-3- P

Pyruvate

Acetyl CoA

NH3

Citric acid

cycle

Oxidative phosphorylation

Fats Proteins Carbohydrates