Required for Life
All living things use oxygen or depend on organisms that use oxygen in some way.
All Animals and Other Consumers
Use Oxygen
We use oxygen to break down simple sugar and release energy.
This can be done through respiration or fermentation.
Animals mainly use respiration.
Respiration
The process that breaks apart simple food molecules to release energy.
It occurs inside cells.
What YOU do with the oxygen you take in.
Simple Sugar — Glucose
The molecule most living things use for energy — including us!
We break down food into smaller molecules during digestion. One of the small molecules is glucose.
Glucose leaves your intestines, goes into your blood and is taken to every cell in your body.
Respiration in Cells
In your cells, oxygen is used to split glucose apart — releasing energy, water and carbon dioxide.
Photosynthesis
Plants take in carbon dioxide and water and use them to make food. Their food is simple sugar — glucose.
Photosynthesis (continued)
Plants pull the carbon off CO2 and use the carbon in glucose. (They do not need the oxygen for this. They get that from water, H2O.)
Plants release the oxygen (O2) back into the atmosphere.
Other organisms use the free oxygen for respiration. How are photosynthesis and cellular respiration similar?
Photosynthesis uses carbon dioxide and produces oxygen.
Cellular respiration uses oxygen and produces carbon dioxide.
Basic idea
Rabbit gives off CO2, which is taken in by the plant.
Rabbit eats food, breaks it down and releases
CO2.
Plant uses CO2 to make food.
Plant gives off O2, which is taken in by the rabbit.
Everywhere
This happens on land and in the water.
Algae and aquatic plants produce food underwater through photosynthesis.
They use CO2 dissolved in the water.