1. Chapter 9.2b
Cellular Respiration

2. Energy and Exercise
When your body needs a lot of energy quickly cells have stored ATP from glycolysis and cellular respiration. After this is used up most ATP is made from lactic acid fermentation.
After you are done sprinting you usually will breathe heavily and quickly – this intake of oxygen is important to break down lactic acid.

3. Long-Term Energy
If you are running a long race you will use the stored ATP, and ATP made from fermentation. Cellular respiration takes longer to make ATP so when you run out of these 2 you will break down stored energy like glycogen or fat to give you more ATP.
This is why exercise can help with weight control.

4. Comparing Photosynthesis and Cellular Respiration
They are kind-of opposites of one another:
Photosynthesis will make carbs, while cell respiration breaks them down.
Photosynthesis uses carbon dioxide and gives off oxygen, while cell respiration uses oxygen and gives off carbon dioxide.