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.