Overview Chapter 5 – Cell Harvest Energy

1. Prokaryotic Cells Overview Chapter 5 – Cell Harvest Energy Eukaryotic Cells

2. Cell Energy Prokaryotic Cells: i.e.. yeast • Fermentation – partial pathway requires no oxygen Eukaryotic Cells: animals - humans • Anaerobic Respiration – partial pathway - no oxygen • Aerobic Respiration - Cellular respiration – oxygen is consumes

3. Fermentation in Yeast

4. Process of alcohol fermentation • Fermentation consists of glycolysis plus reduction of pyruvate to either alcohol and CO2. • NADH passes its electrons to pyruvate instead of to an electron transport system; • NAD+ is then free to return and pick up more electrons during earlier reactions of glycolysis.

5. Anaerobic Fermentation Humans Sometimes Called Lactic Acid

6. Lactic Acid Fermentation • The oxidizing agent of glycolysis is NAD+, not oxygen. • But glycolysis generates 2 ATP. • Fermentation regenerates ATP by transferring electrons to pyruvate.

7. Advantage of Fermentation • provides quick burst of ATP energy for muscular activity.

8. Disadvantage of Fermentation • lactate is toxic to cells. lactate changes pH and causes muscles to fatigue. lactate is sent to liver, converted into pyruvate; then respired or converted into glucose. • Two ATP produced per glucose molecule during fermentation

9. The miracle of fermentation • Glycolysis Animation

10. Cellular Respiration is Aerobic

11. Cellular Respiration • Cellular respiration is the process of oxidizing food molecules, like glucose, to carbon dioxide and water. • The energy released is trapped in the form of ATP for use by all the energy-consuming activities of the cell.

12. The Energy Molecules of Cellular Respiration • ATP – THE ENERGY MOLECULE • NADH – Intermediate Energy Molecule • FADH2 – Intermediate Energy Molecule

13. Remembering ATP

14. FAD and NAD

15. NAD+ and FAD • Each metabolic reaction in cellular respiration is catalyzed by its own enzyme. • As a metabolite is oxidized, NAD+ accepts two electrons and a hydrogen ion (H+); results in NADH + H+. • Electrons received by NAD+ and FAD are high-energy electrons and are usually carried to the electron transport system.

16. Respiration has four distinct stages: 1. Glycolysis (with oxygen) 2. Krebs cycle 3. Electron transport chain 4. Oxidative phosphorylation

17. Glycolysis • Glycolysis is the breakdown of glucose. • It occurs in virtually all cells. • In eukaryotes, it occurs in the cytosol. • C6H12O6 + 2NAD+ -> 2C3H4O3 + 2NADH + 2H+

18. Glycolysis is enzyme driven • Shockwave – observe the step by step process as you look at your book as well as the animation. • Glycolysis • Glycolysis

19. Summary of Yield from Glycolysis The net yield from each glucose molecule is 2 NADH, 2ATP and 2 molecules of pyruvate • An initial investment of 2 ATP yields 4 ATP and 2 NADH or a net gain of 2 ATP and 2 NADH

20. Net from Glycolysis

21. Second Stage of Cellular Respiration The Krebs Cycle – Citric Acid Cycle If molecular oxygen is present the pyruvate enters the mitochondria • Mitochondria are membrane-enclosed organelles distributed through the cytosol of most eukaryotic cells. • Their main function is the conversion of the potential energy of food molecules into ATP.

22. Mitochondria have: • an outer membrane that encloses the entire structure, pyruvate enters the mitochondria first • an inner membrane where electron transport chain (ETC) and ATP Synthase • Matrix where citric acid cycle takes place & Acetyl CoA is converted from pyruvate • between the two membranes is the intermembrane space where all hydrogen's are being pumped during electron transport stage • the inner membrane is elaborately folded with shelflike cristae projecting into the matrix to increase surface area for ETC

24. Prior to entering the Citric Acid Cycle in the Mitochondrial pyruvate must be converted into acetyl CoA. • This is achieved by removing a CO2 molecule from pyruvate and then removing an electron to reduce an NAD+ into NADH. • An enzyme called coenzyme A is combined with the remaining acetyl to make acetyl CoA which is then fed into the Krebs Cycle. The steps in the Krebs Cycle are summarized below:

25. Transition of Pyruvate to Acetyl CoA

26. Summary of Yield from Glycolysis & Conversion to Acetyl CoA The net yield from each glucose molecule is 4 NADH, 2 ATP and 2 molecules of Acetyl CoA

27. Citric Acid Cycle or Krebs Cycle Stage CoA Acetyl CoA CoA 2 carbons enter cycle Oxaloacetate 1 Citrate + H+ NADH NAD+ 5 NAD+ + H+ NADH 2 CITRIC ACID CYCLE leaves cycle CO2 Malate ADP  P FADH2 4 ATP Alpha-ketoglutarate FAD 3 leaves cycle CO2 Succinate NAD+ + H+ NADH Step Acetyl CoA stokes the furnace. Steps – NADH, ATP, and CO2 are generated during redox reactions. Steps – Redox reactions generate FADH2 and NADH. 1 2 3 4 5

28. Key Point to Citric Acid Cycle • Rearranging molecules lead to more energy molecules

29. Energy Molecules – Thus Far So far we have from glycolysis and the Citric Acid cycle: (per molecule of glucose) • 4 ATP (2 used in glycolysis and 2 left) • 10 NADH (needs to be converted to ATP) • 2 FADH2 (needs to be converted to ATP)

30. Electron Transport Chain Stage – Harvest Energy

31. Key Points of Electron Transport Chain • Protons are translocated across the membrane, from the matrix to the intermembrane space • Electrons are transported along the membrane, through a series of protein carriers • Oxygen is the terminal electron acceptor, combining with electrons and H+ ions to produce water • As NADH & FADH2 delivers more H+ and electrons into the ETS, the proton gradient increases, with H+ building up outside the inner mitochondrial membrane.

32. Chemiosmosis or Oxidative Phosphorylation

33. Key Point Chemiosmosis or Oxidative Phosphorylation • As hydrogen diffuses back into the matrix through ATP synthase, converting ADP to ATP

34. Chemiosmosis couples the electron transport chain to ATP synthesis

35. Key Point to the Coupling of Electron Transport to Oxidative Phosphorylation • Intermediate energy molecules through the electron transport chain moves hydrogen ions into the inner membrane space and the resultant hydrogen ion imbalance drives ATP Synthase to produce ATP

36. What happens when oxygen ceases? • Without oxygen electronegetive oxygen to pull the electrons down the transport chain, oxidative phosphorylation ceases. • Fermentation provides another avenue for the synthesis of ATP.

37. ATP Summary • 10 NADH x 3 = 30 ATPs • 2 FADH2 x 2 = 4 ATPs • 2 ATPs (Gly) = 2 ATPs • 2 ATPs (Krebs) = 2 ATPs Max = 38 ATPs per glucose

38. Other Sources of Sugar • Although glucose is considered to be the primary source of sugar for respiration and fermentation, there are actually three sources of molecules for generation of ATP: • Carbohydrates (disaccharides) • Proteins (after conversion to amino acids) • Fats

39. Other Sources of Sugar Food, such as peanuts Carbohydrates Fats Proteins Amino acids Glycerol Sugars Fatty acids Amino groups OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) CITRIC ACID CYCLE Acetyl CoA Glucose G3P Pyruvate GLYCOLYSIS ATP

40. Visit These Sites! • Cell Respiration: Introduction • General & Human Biology • Electron Transport Animations (Mcgraw Hill)