Advanced Topics
In a nutshell: Plants make food from sunlight, and both plants and animals turn that food into energy.
## 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.
Key terms
- Glucose
- A simple sugar used by cells for energy.
- Chlorophyll
- The green pigment in plants that captures sunlight.