Cellular Respiration Lesson for Kids: Definition & Steps

Instructor: Lindsy Frazer

Dr. Frazer has taught several college level Science courses and has a master's degree in Human Biology and a PhD in Library and Information Science.

Are you a fan of sweets? Did you know that cells have a sweet tooth? In fact, cells get all their energy from sugar! Learn about how cells turn sugar into energy through cellular respiration and explore the three steps of cellular respiration in this lesson.

Pass the Sugar

Have you ever felt tired before lunch when you haven't eaten since breakfast? That's because we get our energy from food. Most foods we eat contain a sugar called glucose. Not only does glucose make foods taste sweet, but it is also our cells' main source of energy.

Just like our digestive system breaks down the food we eat, cells must break down glucose to use it. Cells use oxygen to break down glucose and release its energy during a process called cellular respiration. This process is all about changing food into a form of energy cells can actually use called ATP.

Unlike glucose molecules, ATP molecules can be used directly by cells for energy. Cellular respiration is a cell's way of turning the energy found in glucose into ATP to power its functions.


To bake a cake you need eggs and flour. For cellular respiration cells need glucose and oxygen.

When these ingredients are combined three things are made: carbon dioxide, water and energy.

Cellular respiration uses glucose and oxygen to make carbon dioxide, water and energy.

If cellular respiration is all about energy, then what are these other products? When you crack eggs to bake a cake you make some waste- egg shells. When cells are making ATP they also make waste- carbon dioxide and water.

Three Steps

There are three steps to cellular respiration: glycolysis, the Krebs cycle and the electron transport chain.


Glycolysis, pronounced gly-kol-uh-sis, means 'glucose splitting' and that is just what happens during this first step of cellular respiration. A glucose molecule hanging out in a cell is split in half to make two smaller molecules of a chemical called pyruvate. During this splitting some energy- two molecules of ATP- is made. Glycolysis also makes some other energy storing molecules that the cell will use later on to make more ATP.

Krebs Cycle

During the second step of cellular respiration the cell uses oxygen and the pyruvate made during glycolysis to perform several chemical reactions. Like glycolysis, the Krebs cycle makes two molecules of ATP and some other energy storing molecules. But, it also makes the waste product carbon dioxide.

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