1. Cellular Pathways that Harvest Chemical Energy : Respiration

2. Energy flow and chemical recycling

3. Energy For Life
Photosynthesis stores chemical energy into chemical bonds and
Respiration releases the energy stored in the chemical bonds
ATP is the biological currency of Energy

4. Oxidation and Reduction
Gain of one or more electrons by an atom, ion or molecule is called Reduction
Oxidation and Reduction always occurs together, one material is oxidized (loss E) and other is Reduced (Gain E)

5. Oxidized and Reduced NAD
Coenzyme NAD is a key electron carrier in the redox Rxn

6. NAD+ as an electron shuttle

7. Energy Carrier
Oxidizing agent (NAD) accepts E in the process of oxidizing the reducing agent (AH2 to A). Oxidizing agent (NAD) becomes reduced (NADH).
Reducing agent donates E and becomes Oxidized as it reduces the Oxidizing agent (B to BH2)

8. Cellular Energy Pathways

9. Overview of cellular respiration

10. Glycolysis and Fermentation

11. Changes in Free Energy
Each step in glycolysis changes the free energy available
Thus after the step 6 each following steps and metabolites or products will have less energy
First you invest energy then harvest it……

12. Glycolysis: Glucose to Pyruvate
The energy-investing reactions/phase of Glycolysis

13. Glycolysis: Glucose to Pyruvate
Energy-harvesting reactions/phase yields ATP and NADH
Pl note that step 5… each molecule is 2 units because 6C are splits into two 3C molecules
Step 6 to 7 is a substrate-level phosphorylation

14. Substrate-level phosphorylation

15. Glu to Pyr Step 9 to 10 is also a SLP
Glycolysis nets two Molecules of ATP and two Molecules of NADH
4ATP-2ATP=2ATP
In fermentation the net yield is only 2 ATP

16. Pyruvate Oxidation (Mito)
PDC is a large complex, Pyruvate DH converts Pyruvate to Acetyl CoA, releasing first Carbon dioxide
Pyruvate is Oxidized to acetyl group, E conserved in NADH and some energy is conserved by comining acetyl group to CoA

17. Pyruvate to acetyl CoA

18. Citric Acid or TCA Cycle
Acetyl CoA enters the TCA cycle, and CoA regenerated

19. TCA Cycle

20. Closer look at TCA cycle

21. Summary of TCA cycle

22. Free Energy
TCA cycle releases more energy than Glycolysis or pyruvate reduction

23. Oxidation of NADH + H+

24. Resp Chain

25. Chemiosmotic Mechanism

26. ATP Synthesis
ATP synthesis is a reversible reaction and ATP synthase can also act as an ATPase hydrolyzing ATP to ADP
Exergoic Rxn from Et drive the Electrogenic pumping of protons out of Mitochondria into IM space
Pot E of proton gradient has two role, act as channel for protons to diffuse back and it uses E of diffusion to make ATP

27. Chemi-osmotic Mechanism

28. Chemi-osmotic Mechanism
Couples ET to the ATP synthesis using ATP synthase using a Proton Gradient

29. Lactic Acid Fermentation

30. Alcoholic Fermentation

31. Cellular Respiration
Theoretical Net ATP yield from the complete oxidation each glucose molecule is 36 ATP, but never in a living system

32. Cellular Respiration

33. Cellular Respiration

34. ATP molecules during cellular respiration

35. Relationship among the other major Metabolic Pathways

36. Catabolism of various food molecules

37. Coupling Metabolic Pathways
OAA and Asp interconverts, is called Transamination

38. Regul by Negative and Positive Feedback
Excess accumulation of some products can shut down their synthesis or stimulate synthesis of other products

39. Feedback Regulation Citrate and ATP inhibits PFK thus Glycolysis
ADP and AMP stimulates Glycolysis

40. Feedback Regulation ATP and NADH inhibits TCA cycle
Citrate stimulates FA-CoA Rxn
NAD and ADP activated ICDH
ATP and NADH inhibits KGADH

41. Control of cellular respiration

42. Energy flow and chemical recycling

43. Summary
Photosynthesis places energy into chemical bonds and respiration releases it
Glycolysis, TCA cycle,and ET chain and ATP synthesis
Fermentation of pyruvate to lactate or ethanol
Oxidation reduction reactions
Chemiosmotic synthesis of ATP using a proton gradient
Regulation of Metabolic pathways by positive and negative feedback
Various metabolic pathways inter-communicate with each other
Pl read pages for a detailed summary