1. The reason we need to breathe!
Cellular Respiration
The reason we need to breathe!

2. A Video of the Process…

3. What you need to know:
Step 1: Glycolysis – splitting glucose into 2 pyruvate
Step 2: Krebs Cycle (a.k.a. – Citric Acid Cycle) – pyruvic acid is broken down into carbon dioxide through a series of reactions
Step 3: Electron Transport Chain – High energy electrons from Krebs Cycle are used to convert ADP to ATP

4. The particulars… Glycolysis (already covered previously)
Krebs Cycle/Citric Acid Cycle
As pyruvic acid goes through the Krebs Cycle, some of its carbons are released as Carbon Dioxide (CO2)
Other carbons are changed to Acetyl-CoA, Citric Acid, and other compounds
This process transfers high energy electrons to electron carriers NAD+ and FAD

5. The particulars… Electron Transport Chain
High energy electrons from NADH and FADH2 to carrier proteins in the inner membrane of the mitochondria
At the end of the ETC, an enzyme passes the electrons to the “final electron acceptor” = OXYGEN. Hydrogen ions join to make water (H2O).

6. The particulars… 36 ATP molecules are produced from each glucose!
Electron Transport Chain (continued)
Energy from the electrons pumps protons (H+) across the membrane from the matrix to the intermembrane space
As H+ moves back into the matrix, it causes ATP synthase to turn, generating ATP from ADP by attaching a phosphate (“phosphorylation”)
36 ATP molecules are produced from each glucose!

7. Energy and Exercise Quick Energy
Response to danger or a sudden burst of speed by an athlete
Small amount of existing ATP is used up fast
Lactic acid fermentation makes more ATP
Runners breathe hard after running because of their oxygen “debt” which must be paid to rid their muscles of lactic acid

8. Energy and Exercise Long-Term Energy
Extended exercise requires more oxygen
Cellular respiration makes lots of ATP but is slower than fermentation
The body breaks down glycogen (a storage form of carbohydrate) first, then after about 20 minutes of exercise it begins to break down fats
This is why aerobic exercise is good for maintaining a healthy weight.