Cellular Respiration Harvesting Chemical Energy

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phosphorylation:

electron transport

and

chemiosmosis

Citric

acid

cycle

2

Acetyl

CoA

Glycolysis

Glucose

2

Pyruvate

2 NADH

2 NADH

6 NADH

2 FADH2

2 FADH2

2 NADH

CYTOSOL

Electron shuttles

span membrane

or

MITOCHONDRION

Slide 65

Concept 9.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen

Most cellular respiration requires O2 to produce ATP

Glycolysis can produce ATP with or without O2 (in aerobic or anaerobic conditions)

In the absence of O2, glycolysis couples with fermentation or anaerobic respiration to produce ATP

Slide 66

Anaerobic respiration uses an electron transport chain with an electron acceptor other than O2, for example sulfate

Fermentation uses phosphorylation instead of an electron transport chain to generate ATP

Slide 67

Types of Fermentation

Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis

Two common types are alcohol fermentation and lactic acid fermentation

Slide 68

In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO2

Alcohol fermentation by yeast is used in brewing, winemaking, and baking

Animation: Fermentation Overview

Slide 69

Fig. 9-18

2 ADP + 2

Pi

2 ATP

Glucose

Glycolysis

2 NAD+

2 NADH

2 Pyruvate

+ 2 H+

2 Acetaldehyde

2 Ethanol

(a) Alcohol fermentation

2 ADP + 2

Pi

2 ATP

Glucose

Glycolysis

2 NAD+

2 NADH

+ 2 H+

2 Pyruvate

2 Lactate

(b) Lactic acid fermentation

2

CO2

Slide 70

Fig. 9-18a

2 ADP + 2

P

i

2 ATP

Glucose

Glycolysis

2 Pyruvate

2 NADH

2 NAD+

+ 2 H+

CO2

2 Acetaldehyde

2 Ethanol

(a) Alcohol fermentation

2

Slide 71

In lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2

Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt

Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce

Slide 72

Fig. 9-18b