Biology

Study of living organisms and their interactions with the environment.

Advanced Topics

Photosynthesis and Cellular Respiration

How Organisms Get and Use Energy

All living things need energy. Plants and some bacteria make their own food through a process called photosynthesis, while animals and plants break down this food to release energy in a process called cellular respiration.

Photosynthesis

Plants use sunlight, water, and carbon dioxide to make glucose (a sugar) and oxygen.

\[ 6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2 \]

Cellular Respiration

Cells break down glucose with oxygen to release energy, carbon dioxide, and water.

\[ C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy} \]

The Energy Cycle

Photosynthesis and respiration are opposite but connected processes that form the basis of life’s energy flow.

Examples

  • Trees absorb carbon dioxide and produce oxygen for us to breathe.

  • Humans and animals get energy from the food they eat.

In a Nutshell

Plants make food from sunlight, and both plants and animals turn that food into energy.

Key Terms

Glucose
A simple sugar used by cells for energy.
Chlorophyll
The green pigment in plants that captures sunlight.