READ: Energy for your cells

1. Respiration

Why do you need food?

The main reason you need to eat is to get energy. Food is your body's only supply of energy. However, this energy must be converted from pizza (or any other food you eat) into an energy source that your body can use. The process of getting energy from your food is called cellular respiration.

What is Cellular Respiration?

How does the food you eat provide energy? When you need a quick boost of energy, you might reach for an apple or a candy bar. But cells do not "eat" apples or candy bars; these foods need to be broken down so that cells can use them. Through the process of cellular respiration, the energy in food is changed into energy that can be used by the body's cells.

Initially, the sugars in the food you eat are digested into the simple sugar glucose. Recall that glucose is the sugar produced by the plant during photosynthesis. The glucose, is then passed to the organism that eats the plant. This organism could be you, or it could be the organism that you eat. Either way, it is the glucose molecules that holds the energy.

2. ATP

ATP

Specifically, during cellular respiration, glucose is converted into ATP. ATP, or adenosine triphosphate, is chemical energy the cell can use. It is the molecule that provides energy for your cells to perform work, such as moving your muscles as you walk down the street. But cellular respiration is slightly more complicated than just converting glucose into ATP.

Cellular respiration can be described as the reverse or opposite of photosynthesis.

During cellular respiration, glucose, in the presence of oxygen, is converted into carbon dioxide and water. The process can be summarized as:

glucose + oxygen → ATP + carbon dioxide + water

During this process, the energy stored in glucose is converted into ATP.

Energy is stored in the bonds of the ATP molecule. When ATP is broken down energy is released. When ATP is formed, energy is stored. During cellular respiration, about 36-38 ATP molecules are produced for every glucose molecule.

3. Respiration Video

4. Summary and Vocabulary

Summary

• Through the process of cellular respiration, the energy in food is converted into energy that can be used by the body's cells.
• During cellular respiration, glucose and oxygen are converted into ATP, carbon dioxide, and water.

Vocabulary

• ATP (adenosine triphosphate): Usable form of energy inside the cell.

• cellular respiration: Process of breaking down glucose to obtain energy in the form of ATP.
• glucose: Simple sugar with the chemical formula C₆H₁₂O₆; a product of photosynthesis.

CK-12 Foundation, Life Science. http://creativecommons.org/licenses/by-nc-sa/3.0/