Energy at the Botanic Garden

How does cellular respiration work?

by Kyheim Johnson

I walked up to the table and saw water, grape juice, and jade plant juice. I used the liquids that was in the pipette to put on the refractometer. I then shut the lid to the refractometer and looked through it to see the amount of sugar that was in each liquid. The amount of sugar in the grape juice was 15%, water was 0% and the jade plant was 5% A refractometer tells the amount of sugar in a plant. That leaves me with a question, How does the plant turn sugar into energy it can use to grow? The answer to this question is a process called cellular respiration.

A chemical equation is a short way to represent a chemical reaction. A chemical reaction is the process where substances are turned into other substances. In cellular respiration, the reactants are oxygen and glucose. Oxygen is what we use to breathe and glucose is sugar. This means that the plant starts with oxygen and glucose. The reaction turns these reactants into carbon dioxide, water, and ATP. These are called the products. This reaction is important because ATP helps the plants to grow and to stay alive. Especially, because it gives energy.

Cells go through a process called cellular respiration when a plant turns sugar (glucose) into energy. The process includes 4 steps: Glycolysis, Pyruvate Oxidation, Citric Acid Cycle, and Oxidative Phosphorylation. First, a six carbon molecule called glucose goes through a process of transformations where it becomes 2 molecules of pyruvate. During this reaction ATP is made and NAD+ is changed into NADH. Next, the pyruvate molecules go into the mitochondrial matrix. There it is converted into a two carbon molecule bound to Coenzyme A. As a result Carbon Dioxide is released and NADH is generated. Then, in the citric acid cycle acetyl CoA mixes with a four carbon molecule, which then goes through a chain of chemical reactions. In all, ATP, NADH, and FaDH2 are made and carbon dioxide is released. Finally, oxidative phosphorylation takes NADH and FaDH2’s electrons which turns them back to their original forms NAD+ and FADon the electrons transport train. At the end of the electron transport train water is formed. In cellular respiration energy is released allowing the plants to grow. (Source: Khan Academy)

All organisms from all kingdoms of life use cellular respiration. Cellular respiration takes the energy from glucose to help plants. Cellular respiration is the opposite of photosynthesis because it breaks down glucose to release energy. We need energy for plants because they give us food and oxygen.


  • Glucose - Sugar
  • Refractometer - Tool that measures amount of glucose
  • Chemical reaction - Process where substances are turned into other substances
  • Products - Substance that is formed as a result of a chemical reaction
  • Reactants - Substances changed into other substances (products)