1. 2.A.2 Organisms Capture and Store Energy Part II (Cellular Respiration)
Organisms capture and store free energy for use in biological processes.

2. Cellular respiration uses free energy available from sugars to phosphorylate ADP, producing the most common energy carrier, ATP.

3. The free energy available in sugars can be used to drive metabolic pathways vital to cell processes.

4. Cellular respiration involves a series of enzyme-catalyzed reactions that harvest free energy from simple carbohydrates.

5. Cell respiration is a catabolic pathway that yields energy by oxidizing organic fuels.

6. LEO says GERRR
Lose Electrons = Oxidized
Gains Electrons = Reduced

7. The breakdown of organic molecules is exergonic (G >0); the energy released can be harnessed to phosphorylate ADP  ATP.

8. The Three Steps of Cellular Respiration
Krebs
Cycle
Glycolysis
Electron Transport Chain

9. Glycolysis: the breakdown of one glucose molecule into two pyruvate
Glycolysis: the breakdown of one glucose molecule into two pyruvate. It occurs in the cytoplasm and is anaerobic.

10. Glycolysis: Energy Investment Phase
Glucose, a six carbon sugar, is split into two 3-carbon molecules.
Requires 2 ATP

11. Glycolysis: Energy Payoff Phase
The two 3-carbon molecules are converted into two pyruvate.
Produces 2 NADH and 4 ATP

12. Glycolysis: Summary Investment: Payoff: Glucose
4 ATP formed – 2 ATP used
2 NAD+
Payoff:
2 Pyruvate
2 ATP
2 NADH
Oxidation
Reaction

13. Pyruvate is transported from the cytoplasm to the mitochondrion, where it is converted to Acetyl CoA.

14. Transition Reaction: Payoff: Investment: 2 Acetyl Coenzyme A 2 NADH
2 Pyruvate
Payoff:
2 Acetyl Coenzyme A
2 NADH
2 CO2 (waste product)

15. The Krebs Cycle (Also known as the Citric Acid Cycle or the TCA Cycle)

16. The Krebs Cycle occurs in the matrix of the mitochondria.

17. The Krebs Cycle produces 2 ATP through substrate-level phosphorylation
The Krebs Cycle produces 2 ATP through substrate-level phosphorylation. (Must occur twice for one glucose to be consumed).

18. The Krebs Cycle produces 2 ATP through substrate-level phosphorylation.

19. During the Krebs Cycle , coenzymes NAD+ and FADH each receive high energy electrons and become NADH and FADH2.

20. The Krebs Cycle Summary:
Investment:
2 Acetyl CoA
Payoff:
2 ATP
6 NADH
2 FADH2
4 CO2 (waste)
Substrate-Level
Phosphorylation

21. The Electron Transport Chain is imbedded in the inner mitochondrial membrane.

22. Electrons that were extracted in the Krebs cycle are carried by NADH and FADH2 to the Electron Transport Chain.

23. The electrons are passed from one carrier to the next until they are ultimately accepted by oxygen, forming water. (Oxygen is the final electron acceptor.)

24. The energy from the electrons is used to pump protons into the intermembrane space, forming an electrochemical gradient.

25. The protons diffuse through ATP synthase (chemiosmosis), which uses the energy of the gradient to synthesize ATP from ADP. This type of ATP synthesis is called Oxidative Phosphorylation.

26. The Electron Transport Chain occurs on the cell membrane of prokaryotes.

27. The Electron Transport Chain Summary:
Investment:
10 NADH
2 FADH2
Oxygen
Payoff:
32-34 ATP
H2O
Oxidative
Phosphorylation

28. Cellular Respiration Summary:
Investment:
1 glucose
oxygen
Payoff:
Water
CO2
36-38 ATP
Yields 686 kcal energy per mole of glucose oxidized!

29. Cellular respiration also occurs in plants, along with photosynthesis.

30. Endotherms can decouple oxidative phosphorylation from the electron transport to produce more body heat instead of ATP.

31. Different energy-capturing processes use different types of electron acceptors:
NADP+ for photosynthesis
Oxygen for cellular respiration

32. In the absence of oxygen, ATP production can continue
In the absence of oxygen, ATP production can continue. This is called fermentation.

33. There are two types of fermentation:
Lactic Acid Fermentation
Animals
Ethanol Fermentation
Yeast

34. Fermentation produces ATP through substrate-level phosphorylation when the ETC cannot run due to lack of oxygen.

35. Lactic Acid Fermentation

36. Ethyl Alcohol Fermentation

37. Fermentation Summary:
Investment:
1 glucose
Payoff:
2 ATP
2 CO2
Anaerobic

38. Heterotrophs may metabolize carbohydrates, lipids and proteins by hydrolysis as sources of free energy.
Hydrolysis:

40. Photosynthesis and Cellular Respiration are mirror reactions.

41. Learning Objectives
LO 2.4 The student is able to use representations to pose scientific questions about what mechanisms and structural features allow organisms to capture, store and use free energy. [See SP 1.4, 3.1]
LO 2.5 The student is able to construct explanations of the mechanisms and structural features of cells that allow organisms to capture, store or use free energy. [See SP 6.2]