1. How living things get energy from food.
Cellular Respiration
How living things get energy from food.

2. All living things need Food to Survive.
All living organisms must get their energy from food.
Autotrophs can make their own food, but still must break it down to use the energy in the food.
Heterotrophs get their food by eating other organisms.

3. Food Energy
The energy in food is measured in units called calories. (Notice the lowercase “c”).
One calorie is the amount of energy it takes to raise 1 gram of water 1 degree Celsius.
This is very little energy, so in the US we label food with Kilocalories or Calories (notice the uppercase “C”).
Each Kilocalorie is worth 1000 calories.

4. Energy in Food
Our bodies use the energy stored in the bonds of food molecules to make ATP, the molecule that powers all life.

5. How do cells unlock food energy?
Cells use a process called Cellular Respiration to unlock the energy stored in food.
Cellular respiration is the process that releases energy from food in the presence of oxygen.

6. Cellular Respiration
Cellular Respiration works by taking sugar and using oxygen to break it into carbon dioxide, water and energy.
Notice that Cellular Respiration can only be done if oxygen is present.

7. The Equation for Cellular Respiration:
In words:
Oxygen + Glucose  Carbon Dioxide + Water + Energy
In Symbols:
6 O2 + C6H12O6  6 H2O + 6 CO2 + Energy

8. How does Cellular Respiration Work?
Cells have to release energy from food slowly, otherwise much of the energy would be lost as heat or light.
Cellular Respiration uses three steps to release energy
Glycolysis
Krebs Cycle
Electron transport chain

9. Glycolysis Glycolysis is the first step in Cellular Respiration.
Glycolysis occurs in the cytoplasm.
Glycolysis breaks the glucose molecule in to two separate pieces.
Glycolysis only releases 2 ATP.
After glycolysis, 90% of the energy is still locked up in the food molecule.
Glycolysis does not need oxygen to occur.

10. Krebs Cycle and Electron Transport Chain
The Krebs Cycle and the Electron Transport chain both occur in the mitochondria.
The produce the bulk of the energy in Cellular Respiration.
In order for the Electron Transport Chain to occur, oxygen molecules must be present.

11. Aerobic and Anaerobic Reactions
In order for Cellular Respiration to occur, oxygen must be present.
When a reaction needs oxygen in order to happen, it is called an Aerobic reaction.
When a reaction does not need oxygen in order to happen, it is called an anaerobic reaction.

12. Cellular Respiration
What kind of process is Glycolysis? Aerobic or Anaerobic?
What kinds of processes are the Krebs Cycle and the Electron Transport Chain? Aerobic or Anaerobic?

13. Comparing Cellular Respiration and Photosynthesis
By now you may have noticed Cellular Respiration and Photosynthesis are similar processes, but opposite.
Consider: Photosynthesis
Water + Carbon Dioxide + Sun energy  Oxygen + Sugar
Cellular Respiration:
Oxygen + Sugar  Water + Carbon Dioxide + Energy

15. Photosynthesis and Cellular Respiration
Photosynthesis occurs in the chloroplast of the cell.
Cellular Respiration occurs in the mitochondria.
Photosynthesis is energy storing, and cellular respiration is energy releasing.