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3.43: Cellular Respiration Reactions

Difficulty Level: At Grade Created by: CK-12
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“Now, take a deep breath so I can listen to your lungs.” Did your doctor ever tell you that, while listening to your back or chest with a stethoscope? Breathing is often referred to as respiration. When you breathe, you take oxygen into your lungs as you inhale, and you release carbon dioxide and water vapor as you exhale. Inside all the cells of your body, a different kind of respiration takes place. This kind of respiration is called cellular respiration.  

What is Cellular Respiration?

Cellular Respiration is the process in which the cells of living things break down the organic compound glucose with oxygen to produce carbon dioxide and water. The overall chemical equation for cellular respiration is:

C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O

As the Figure below shows, cellular respiration occurs in the cells of all kinds of organisms, including those that make their own food (autotrophs) as well as those that get their food by consuming other organisms (heterotrophs).

Cellular respiration occurs in all organisms

Q: How is cellular respiration related to breathing?

A: Breathing consists of inhaling and exhaling, and its purpose is to move gases into and out of the body. Oxygen needed for cellular respiration is brought into the body with each inhalation. Carbon dioxide and water vapor produced by cellular respiration are released from the body with each exhalation.

Energy Changes in Cellular Respiration

The reactions of cellular respiration are catabolic reactions. In catabolic reactions, bonds are broken in larger molecules and energy is released. In cellular respiration, bonds are broken in glucose, and this releases the chemical energy that was stored in the glucose bonds. Some of this energy is converted to heat. The rest of the energy is used to form many small molecules of a compound called adenosine triphosphate, or ATP. ATP molecules contain just the right amount of stored chemical energy to power biochemical reactions inside cells. You can see these energy changes in cellular respiration in the video at this URL: http://www.youtube.com/watch?v=JyMfKP1D7OE .


  • Cellular respiration is the process in which the cells of all living things break down glucose with oxygen to produce carbon dioxide and water.
  • Cellular respiration is a catabolic process that releases energy by breaking bonds in glucose. It uses the energy to form ATP, a small molecule that stores just the right amount of energy for cells to use.

Explore More

Watch the video about cellular respiration at the following URL, and then compare and contrast the two types of cellular respiration.



  1. What is cellular respiration?
  2. Represent cellular respiration with a chemical equation.
  3. Explain why cellular respiration is a catabolic reaction.
  4. What happens to the energy that is released when bonds are broken in glucose molecules?


cellular respiration

cellular respiration

Process in which the cells of living things break down glucose with oxygen to produce carbon dioxide, water, and energy.

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Difficulty Level:

At Grade


7 , 8

Date Created:

Nov 14, 2012

Last Modified:

Feb 19, 2015
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