1. Respiration

2. Respiration is an ambiguous term
Can refer to the process of gas exchange in organisms (breathing, ventilation).
Can refer to a complex metabolic process called cellular respiration

3. Cellular respiration
Oxidation of cellular fuels (sugars, fats, proteins)
Occurs in cells of nearly all organisms
The process utilizes O2 and produces CO2
As fuels are oxidized, some energy is transferred from fuel molecules to ATP
The ATP can then be used as a direct source of energy for any cellular process that requires energy

4. Overall Process: cellular respiration
When glucose is the fuel:
C6H12O6 + 6 O2  6 CO2 + 6H2O + 36 ATP

5. Ventilation (breathing)
Way of acquiring O2 from the environment
Way of disposing of CO2 to the environment

6. How does respiration affect the composition of the atmosphere?
Increases [CO2]
Decreases [O2]