2. Most people think that, respiration is the process where we take air into our lungs…
…and then expel it. We repeat this process rhythmically and automatically.
For scientists, this process is not respiration, it is just one part of it: lung ventilation.

3. It starts when, after we take in air.
Respiration is a more complex process:
It starts when, after we take in air.
We take in air
Oxygen
Oxygen passes from the pulmonary alveoli into the blood.

4. The blood carries the oxygen collected by the alveoli to cells throughout the body.

5. The oxygen enters the cells directly through the membrane…
…and goes into the mitochondria.
Oxygen
An energy nutrient (called glucose) also goes into the mitochondria.
Glucose

6. This process is cellular respiration.
• In the mitochondria, the oxygen (O2) reacts with the glucose in complicated chemical process, which transform them into simple molecules, such as carbon dioxide (CO2) and water (H2O) and also releases energy. O2
Molecules of glucose (rich in energy)
CO2 + H2O
ENERGY
This process is cellular respiration.

7. • One result of cellular respiration in the mitochondria is the production of a waste product, CO2, which is expelled from the cell through the membrane.
CO2

8. • The CO2 from the cell activity is collected by the blood in the circulatory system.

9. When we breathe out, we expel the CO2.
• Finally, the CO2 is carried by the blood to the lungs, where it passes into the air contained in the pulmonary alveoly.
CO2
When we breathe out, we expel the CO2.