1. Respiration

2. Chemical Cycling Cellular Respiration C 6 H 12 O 6 +O 2  CO 2 +H 2 O Photosynthesis CO 2 +H 2 O  C 6 H 12 O 6 +O 2 Why do we need to eat food?

3. Respiration and Breathing How does cellular respiration relate to breathing? How exactly is O 2 used in the cells? Why exactly do we breath out CO 2 ?

4. Cellular Reactions What type of bond holds food molecules together?

5. Cellular Reactions What type of bond holds food molecules together? Covalent bonds: sharing of electrons When looking at the formulas, we are looking at the transfers of electrons

6. Redox Reactions Chemical reactions that transfer electrons from one substance to another Oxidation: loss of electrons from a molecule Reduction: gain of electrons

7. Redox Reactions

8. When electrons change partners, from sugar to oxygen, energy is released Why?

9. Redox Reactions When electrons change partners, from sugar to oxygen, energy is released Why? Because electrons are being transferred from a less stable molecule (sugar) to a more stable molecule (O 2 ) Remember, the less stable the molecule, the more potential energy O 2 is one of the most stable molecules and its used by cells to cause redox reactions

10. Redox Reactions As electrons are passed from a less stable to a more stable molecule, energy is released This energy is used to recycle ADP to ATP

11. Cells Must Be Efficient What would happen if our cells burn glucose (releasing electrons) all at once?

12. The “Fall” of Electrons

13. Two Ways We Generate ATP

14. A Closer Look Cellular Respiration has three main stages Glycolysis Krebs Cycle Electron Transport Chain You need to know: The purpose of each stage Where it takes place

15. A Closer Look Glycolysis “sugar splitting” Glucose is split in two Makes it easier to harvest electrons in the glucose molecule Takes place in cytosol Because glucose is split (less stable to more stable), a little energy is released to make ATP

16. Glycolysis Summary

17. Glycolysis  Krebs Cycle Pyruvic Acid Two molecules from glycolysis (cytoplasm) Enters mitochondria PA does not enter Krebs cycle Two Acetyl-CoA

18. A Closer Look Krebs Cycle Completely strips the split sugar molecules of their electrons Electrons are carried off by NADH & FADH 2 A waste product is produced (CO 2 ) A small amount of energy is used to make ATP Takes place in mitochondria fluid

19. Chemiosmosis Electron Transport Chain Electrons captured by NADH are passed down a chain of proteins O 2 is the final electron acceptor (most stable) Energy is released as electrons are passed down the chain to O 2 This energy is used to make ATP….but how?

20. The ETC: Review

21. Summary

22. What If O 2 is Absent? When muscles are over worked, they run out of O 2 Without O 2, the Krebs Cycle and ETC shut down Glycolysis produces small amounts of energy and lactic acid (ethyl alcohol) Lactic Acid

25. Summary We need the electrons in food to drive the synthesis of ATP We need O 2 because it’s a stable electron acceptor and therefore runs the ETC CO 2 is a waste product produced after foods have been completely stripped of their electrons (exhale out lungs) Cellular respiration is a three stage process