1. Cellular Respiration Harvesting Chemical Energy

2. Energy All living things need energy Energy comes from food when broken down Energy is stored in chemical bonds (chemical energy) Energy can be obtained from carbohydrates, fats, and proteins Simple carbohydrates are broken down the fastest Glucose is our main energy source

3. Cellular Respiration Process that releases energy by breaking down glucose in the presence of oxygen Also called aerobic respiration C 6 H 12 O 6 + 6O 2  6CO 2 +6H 2 O + energy (ATP and heat) Glucose + oxygen  carbon dioxide + water + energy (ATP and heat)

4. ATP Nucleotide with three phosphates Energy for cells Energy is stored in the bond between the second and third phosphate group By breaking this bond, energy is released

5. ATP When ATP loses a phosphate group, it becomes ADP Energy released Energy can be stored by adding a phosphate back to ADP

6. ATP Can be used to power : Active transport Protein synthesis Muscle contraction And many, many more However, cells don’t keep a lot of ATP on hand Cells store glucose, which can be used to produce ATP when needed!

7. Electron Carriers Electrons have energy, so……. Transferring electrons transfers energy Electrons are transferred in the form of a hydrogen (H+ and 2e-) In cellular respiration, certain molecules act as electron carriers (store energy to be used later) NAD + : becomes NADH FAD +2 :becomes FADH 2

8. Cellular Respiration Although it seems like cellular respiration is one big step, it actually takes place in a series of smaller steps This keeps the cells from having one big explosion of energy that could be wasted as light and heat

9. Cellular Respiration Three main steps: Glycolysis  starts the breakdown of glucose Occurs in the cytoplasm and doesn’t require oxygen The Krebs Cycle  completes the breakdown of glucose Occurs in the mitochondria and requires oxygen Electron Transport Chain  produces most of the ATP Occurs in the mitochondria and MUST HAVE oxygen

10. Mitochondria Double membrane structure (inner and outer) Inner membrane has several folds (cristae) Intermembrane space – between inner and outer membrane Matrix – space within the cristae

11. Cellular Respiration

12. Glycolysis 10 step process in which one molecule of glucose (6-carbons) is broken into two pyruvic acids (3-carbons)

13. Glycolysis 2 ATPs are used at the beginning of glycolysis Outcome: 4 ATP are produced 2 NADH are formed Net gain: 2 ATP 2 NADH (to be used later!!!)

14. The Krebs Cycle (Citric Acid Cycle) Takes place in the matrix In the presence of oxygen, pyruvic acid is broken down into carbon dioxide

15. The Krebs Cycle Since there are 2 pyruvic acids, there are two turns of the cycle for each glucose Total Outcome: 2 ATP 6 NADH (to be used later) 2 FADH 2 (to be used later) 6 CO 2 (exhaled)

16. Electron Transport Chain The ETC is a series of proteins on the cristae Electrons from NADH and FADH 2 are passed through the ETC towards O 2 OXYGEN IS THE FINAL ELECTRON ACCEPTOR OXYGEN DRIVES THE WHOLE PROCESS!!! Energy from electrons used to pump H+ ions, creating a concentration gradient (stores potential energy) At the end of the chain, the electrons and H+ are combined with oxygen to form water

17. ETC

18. ATP Synthesis The H+ ions now flow (high to low) back across the membrane through ATP synthase, a channel protein Energy in the flow! Flow provides energy to make lots of ATP!!! (P is added to ADP) Approximately 32 ATP are made

19. Why is oxygen necessary? The presence of O 2 drives the movement of electrons. At the end of the chain, the electrons and H+ are combined with oxygen to form water If oxygen is not present, the movement of electrons stop Oxygen is the final electron acceptor!

20. Final Count Glycolysis – 2 ATP Krebs Cycle – 2 ATP Electron Transport Chain ~ 32 ATP Total: ~ 36 ATP per 1 glucose Other products include H 2 0 and CO 2 Remember: C 6 H 12 O 6 + 6O 2  6CO 2 +6H 2 O + energy (ATP and heat)

21. If oxygen is not present… After glycolysis, the pyruvic acids will enter a different pathway Called fermentation No oxygen = Anaerobic respiration Electron carriers are recycled so glycolysis can continue to produce ATP Less efficient (only 2 ATP at a time!)

22. Two Types of Fermentation Alcoholic fermentation pyruvic acid is broken down to form ethyl alcohol and CO 2 Used by yeast and some bacteria Used to make bread and wine

23. Two Types of Fermentation Lactic acid fermentation Pyruvic acid is broken down into lactic acid Occurs during rapid exercise when the body begins to run low on oxygen Used to make cheese, yogurt, pickles, etc