Photosynthesis and Cellular Respiration

​The two equations are the reverse of each other. The products of one reaction become the reactants of the other reaction.

​In a previous lesson, you learned about the chemical equations for photosynthesis and cellular respiration. Today, you will learn more about each process. You will learn the following about both photosynthesis and cellular respiration:

• a description of the process

• what organelle performs the process

• the reactants

• the products

• the types of organisms that perform the process

Chloroplasts Explained

​Many people think of plants when they hear the word photosynthesis. Although plants are common photosynthetic organisms, they are not the only organisms that use photosynthesis. Organisms that perform photosynthesis include:

• most, but not all, plants

• some protists

• algae

• cyanobacteria

About 50% of the oxygen in Earth's atmosphere is produced by algae and protists in the ocean.

​Several types of organisms perform photosynthesis. During photosynthesis, chloroplasts use carbon dioxide and water to produce oxygen and the sugar glucose. Cellular respiration shares many similarities with photosynthesis.

​Cellular Respiration Video

Cellular respiration is the process that cells use to release the energy that is stored in sugar molecules. Cells convert oxygen and glucose into carbon dioxide and water. Cellular respiration transfers the energy from the glucose molecule to another molecule, ATP, that the cell uses for energy later. Cells use the energy to move, reproduce, and produce proteins.

​Photosynthesis and cellular respiration are opposite chemical reactions. The products of photosynthesis are the reactants of cellular respiration. The equation for cellular respiration is:

Cellular respiration occurs in the mitochondria of a cell. Recall that only eukaryotes contain membrane-bound organelles such as mitochondria.

All eukaryotes, including plants and animals, perform cellular respiration. Organisms from the domains Bacteria and Archaea use a different method to gain energy from food. The type of respiration Bacteria and Archaea perform does not use oxygen or mitochondria.

​Cellular respiration and photosynthesis are closely related chemical reactions. Both equations involve the same molecules, although the arrangement of those molecules in the equations differs. Some organisms perform both processes, while other organisms only perform cellular respiration.