1

Cellular Respiration and Fermentation

Chapter 9

2

Sunlight Powers Life

3

Making Chemical Energy Available for Cellular Work

Cells break complex organic molecules into smaller molecules with less chemical energy

This process is called cellular respiration

Glucose + Oxygen → Carbon Dioxide + Water + Energy

40%

Chemical

60%

Thermal

4

Measuring Energy

Energy is measured in units called calories

A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1◦C

1000 calories = 1 kcal or Calorie (a nutritional calorie)

However, food is not used directly by cells to do work, it must be converted into another usable form called ATP.

5

What is ATP?

ATP is called the "currency" of the cell– ATP is a small packet of Energy that can be used a

little at a time, like coins– ATP is constantly reused and recycled– You can’t buy things without $$, cells can’t Work

without Energy from ATP

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Chemical Energy and ATP

– Storing Energy ADP has two phosphate groups instead of

three. A cell can store small amounts of energy by

adding a phosphate group to ADP.

ADPATP

Energy

Energy

Partiallycharged battery

Fullycharged battery

+

Adenosine Diphosphate (ADP) + Phosphate

Adenosine Triphosphate (ATP)

7Copyright Pearson Prentice Hall

Chemical Energy and ATP

P

ADP

2 Phosphate groups

– Releasing Energy

Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates.

8

The ATP Cycle

ATP → ADP + phosphate + energy for Work

ADP + Energy (from food) + phosphate → ATP

9

A Metabolic Pathway called Cellular Respiration

Cells harvest energy by breaking bonds and shifting electrons from one molecule to another.– aerobic respiration - final electron acceptor is

oxygen

– anaerobic respiration - final electron acceptor is a molecule other than oxygen

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Aerobic RespirationC6H12O6 + 6O2 → 6CO2 + 6H2O + Energy

Occurs in 3 Stages:1. Glycolysis2. The Kreb’s Cycle3. Electron Transport Chain and ATP Synthase

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Adding up the ATP from Cellular Respiration

Mitochondrion

Glycolysis

Glucose2

Pyruvicacid

2Acetyl-

CoA

KrebsCycle

ElectronTransport

MaximumATP perglucose:

ATP Synthase

CO2 H2O

O2

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Harvesting Energy WITHOUT Oxygen

• If oxygen is not available to capture the 2 low energy electrons at the end of the ETC, the Kreb’s cycle and the ETC will stop producing ATP

• Glycolysis will continue to generate 2 ATP molcules, 2 NADH, and 2 Pyruvic Acid molecules

• NADH reacts with the pyruvic acid, making NAD+ available to carry electrons so glycolysis can continue making ATP

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Two Types of Fermentation

ALCOHOLICPyruvic Acid → CO2 + ethyl alcohol

• Occurs in yeast• CO2 makes dough rise

and bubbles in beer & champagne

• Ethyl alcohol makes alcoholic beverages

LACTIC ACIDPyruvic Acid → Lactic Acid

• Occurs in muscles during vigorous exercise (can feel “burn”)

• Occurs in prokaryotes used to make cheese, yogurt, sour cream, and sauerkraut