Cellular Respiration: Harvesting Energy From Food CHAPTER 6 Energy Flow and Cycling in the Biosphere Cellular Respiration o Overview of Equation o

Cellular Respiration: Harvesting Energy From Food CHAPTER 6Cellular Respiration: Harvesting Energy From Food CHAPTER 6

Energy Flow and Cycling in the Biosphere

Cellular Respiration

o Overview of Equation

o Oxidation Reactions and Electron Carriers

o Steps of Cellular Respiration

Alternate Fuels and Total ATP

Getting By Without Oxygen: Fermentation

Fact About Energy Use and Breathing

Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

• Aerobic metabolism

– Occurs when enough oxygen reaches cells to support energy needs.

• Anaerobic metabolism

– Occurs when the demand for oxygen outstrips the body’s ability to deliver it.

Energy Flow and Chemical Cyclingin the Biosphere

• Fuel molecules in food represent solar energy.

– Energy stored in food can be traced back to the sun.

• Animals depend on plants to convert solar energy to chemical energy.

– This chemical energy is in the form of sugars and other organic molecules.



• Autotrophs

– Are “self-feeders.”

– Include plants and other organisms that make all their own organic matter from inorganic nutrients.

• Heterotrophs

– Are “other-feeders.”

– Include humans and other animals that cannot make organic molecules from inorganic ones.


• Producers

– Biologists refer to plants and other autotrophs as the producers in an ecosystem.

• Consumers

– Heterotrophs are consumers, because they eat plants or other animals.

Chemical Cycling between Photosynthesis and Cellular Respiration

• The ingredients for photosynthesis are carbon dioxide and water.

– CO2 is obtained from the air by a plant’s leaves.

– H2O is obtained from the damp soil by a plant’s roots.

• Chloroplasts rearrange the atoms of these ingredients to produce sugars (glucose) and other organic molecules.

– Oxygen gas is a by-product of photosynthesis.Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

Figure 6.3

Figure 6.4









Unnumbered Figure 6.1


• The loss of electrons during a redox reaction is called oxidation.

• The acceptance of electrons during a redox reaction is called reduction.

Unnumbered Figure 6.2

Figure 6.6

The path that electrons take on their way down from glucose to oxygen involves many steps


The Metabolic Pathway of Cellular Respiration

• Cellular respiration is an example of a metabolic pathway,

– A series of chemical reactions in cells.

• All of the reactions involved in cellular respiration can be grouped into three main stages:

– Glycolysis

– The Krebs or Citric Acid Cycle

– Electron transport

Figure 6.7

Path of glucose through cellular respiration

Figure 6.8

Glycolysis

Figure 6.9

Some ATP Made By Enzymatic Transfer of Phosphate to ADP

Figure 6.10

Preparation Step Before the Krebs/Citric Acid Cycle

Figure 6.11

Figure 6.12

Electron Transport Chain and ATP “Mill”

Figure 6.14

Total ATP Made During Cellular Respiration









Figure 6.13

May Types of Food Can Generate ATP in Cell Respiration










Fermentation: Anaerobic Harvest of Food Energy

• Some of your cells can actually work for short periods without oxygen.

• Fermentation

– Is the anaerobic harvest of food energy.

• After functioning anaerobically for about 15 seconds,

– Muscle cells will begin to generate ATP by the process of fermentation.

• Fermentation relies on glycolysis to produce ATP.


• Glycolysis is the metabolic pathway that provides ATP during fermentation.

– Pyruvic acid is reduced by NADH, producing NAD+, which keeps glycolysis going.

– In human muscle cells, lactic acid is a by-product.

Figure 6.15a

Fermentation Overview

Fermentation By Bacteria and Human Muscle Cells

Figure 6.15b

Fermentation By Yeast Cells

Figure 6.16









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Cellular Respiration: Harvesting Energy From Food CHAPTER 6 Energy Flow and Cycling in the Biosphere Cellular Respiration o Overview of Equation o