Cellular Respiration Harvesting Chemical Energy

Page
3

Free energy, G

(a) Uncontrolled reaction

H2O

H2 + 1/2 O2

Explosive

release of

heat and light

energy

(b) Cellular respiration

Controlled

release of

energy for

synthesis of

ATP

2 H+ + 2 e–

2 H

+

1/2 O2

(from food via NADH)

ATP

ATP

ATP

1/2 O2

2 H+

2 e–

Electron transport

chain

H2O

Slide 21

The Stages of Cellular Respiration: A Preview

Cellular respiration has three stages:

Glycolysis (breaks down glucose into two molecules of pyruvate)

The citric acid cycle (completes the breakdown of glucose)

Oxidative phosphorylation (accounts for most of the ATP synthesis)

Slide 22

Fig. 9-6-1

Substrate-level

phosphorylation

ATP

Cytosol

Glucose

Pyruvate

Glycolysis

Electrons

carried

via NADH

Slide 23

Fig. 9-6-2

Mitochondrion

Substrate-level

phosphorylation

ATP

Cytosol

Glucose

Pyruvate

Glycolysis

Electrons

carried

via NADH

Substrate-level

phosphorylation

ATP

Electrons carried

via NADH and

FADH2

Citric

acid

cycle

Slide 24

Fig. 9-6-3

Mitochondrion

Substrate-level

phosphorylation

ATP

Cytosol

Glucose

Pyruvate

Glycolysis

Electrons

carried

via NADH

Substrate-level

phosphorylation

ATP

Electrons carried

via NADH and

FADH2

Oxidative

phosphorylation

ATP

Citric

acid

cycle

Oxidative

phosphorylation:

electron transport

and

chemiosmosis

Slide 25

The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions

BioFlix: Cellular Respiration

Slide 26

Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration

A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation

Slide 27

Fig. 9-7

Enzyme

ADP

P

Substrate

Enzyme

ATP

+

Product

Slide 28

Concept 9.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

Glycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvate