What Is the Purpose of Cellular Respiration?

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  • 1:35 Stages Of Cellular Respiration
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Lesson Transcript
Jessica Franciosi
Expert Contributor
Christianlly Cena

Christianlly has taught college physics and facilitated laboratory courses. He has a master's degree in Physics and is pursuing his doctorate study.

In this lesson, explore cellular respiration and its purpose. You'll see the differences between anabolic and catabolic reactions and understand how our bodies are able to utilize the energy stored in the foods we eat.

The Purpose Cellular Respiration

Cellular respiration is the process by which cells in plants and animals break down sugar and turn it into energy, which is then used to perform work at the cellular level. The purpose of cellular respiration is simple: it provides cells with the energy they need to function. If living things could not get the energy they need out of food, it would be absolutely worthless. All living things would eventually die, no matter the quality and amount of food.

Cellular respiration is used to create usable energy from the foods that living things eat. It's important to know that the reactions involved in cellular respiration are catabolic, meaning they break down molecules into smaller ones. This differs from anabolic reactions, which build bigger molecules from smaller ones. Key point: Cellular respiration involves catabolic reaction in order to break down food into usable energy so that cells, and the living organisms that contain them, can survive and thrive.

Cellular Respiration: What's Involved?

There are many stages involved in cellular respiration. It begins with glucose (glucose is known as sugar) and results in energy in the form of ATP (adenosine triphosphate). Are you ready for the fancy science equation? Here it is:


As you can see, cellular respiration begins with one molecule of glucose and some oxygen (the oxygen is in the air that we breathe and is required for cellular respiration), and the end product is energy, with carbon dioxide and water as byproducts.

Stages of Cellular Respiration

There are three important stages of cellular respiration, and they are important to recognize. The first stage is glycolysis, the initial process by which glucose is converted into pyruvate. Next, there's the Krebs Cycle, which converts pyruvate into different metabolites and generates energy (ATP) by doing so. Lastly there is the electron transport chain, which uses ATP to move electrons down a membrane (and this generates even more energy).

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Additional Activities

True or False Activity on Cellular Respiration

In this activity, you'll check your knowledge of cellular respiration, and its purpose as presented in the lesson.


Determine whether the following statements are true or false. To do this, print or copy this page on a blank paper and underline or round the answer.

1. Anabolic reactions are characterized by the release of energy and breakdown of molecules.

True | False

2. Cellular respiration is a process that converts chemical energy from oxygen molecules to ADP.

True | False

3. In the Krebs cycle, pyruvate transforms into metabolites that generate ATP.

True | False

4. The disintegration of molecules is necessary to make them easier to utilize.

True | False

5. The reaction between hydrogen and the glucose marks the start of cellular respiration.

True | False

6. Oxygen is a gas that assists in cellular respiration by reacting with glucose to produce a usable form of energy.

True | False

7. The cycle of cellular respiration and photosynthesis is essential to sustain life.

True | False

8. Carbon dioxide is a principal source of energy for cellular respiration.

True | False

9. Adenosine triphosphate (ATP) is an organic molecule that provides energy to drive many processes in living cells.

True | False

10. Gluconeogenesis is the cellular degradation of the simple sugar glucose to yield pyruvate.

True | False

Answer Key

1. False, because the correct statement is, Catabolic reactions are characterized by the release of energy and breakdown of molecules.

2. False, because the correct statement is, Cellular respiration is a process that converts chemical energy from oxygen molecules to ATP.

3. True

4. True

5. True

6. True

7. True

8. False, because the correct statement is, Glucose is a principal source of energy for cellular respiration.

9. True

10. False, because the correct statement is, Glycolysis is the cellular degradation of the simple sugar glucose to yield pyruvate.

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