Chapter 5

1. Chapter 5 ATP Cell Respiration & Metabolism 5-1

2. ATP Fig 4.15 4-27

3. Oxidation-Reduction continued Fig 4.17 4-29

4. Metabolism • Is all reactions in body that involve energy transformations • Divided into 2 categories: • Catabolism breaks down molecules & releases energy • Is primary source of energy for making ATP • Anabolism makes larger molecules & requires energy • Source of body’s large energy-storage compounds 5-3

5. Carbohydrates Fig 2.13 • Are organic molecules containing carbon, hydrogen & oxygen in ratio of CnH2n0n • Monosaccharides are simple sugars such as glucose, fructose, galactose 2-29

6. Glycolysis • Is metabolic pathway by which glucose is converted to 2 pyruvates • Does not require oxygen • Overall net equation is: • glucose + 2NAD + 2ADP + 2Pi  2 pyruvates + 2NADH + 2 ATP 5-5

7. Glycolysis continued • Glycolysis is exergonic - produces net of 2ATPs & 2NADHs • However, glucose must be activated with 2ATPs (phosphorylation) before energy can be obtained • Phosphorylation traps glucose inside cell • Below can see 2ATPs added & 4 are produced for a net gain of 2 ATP Fig 5.1 5-6

8. Glycolysis continued Fig 5.2 5-7

9. Lactic Acid Pathway • To avoid end-product inhibition, NADHs produced in glycolysis need to give Hs away • In absence of O2, NADH gives its Hs to pyruvate creating lactic acid (anaerobic respiration) • Makes muscles feel fatigued Fig 5.3 5-8

10. Lactic Acid Pathway continued • RBCs don't have mitochondria; use only lactic acid pathway • Occurs in skeletal & heart muscle when oxygen supply falls below critical level • During heavy exercise or vascular blockage 5-9

11. Aerobic Respiration • Begins when pyruvate formed by glycolysis enters mitochondria • C02 is clipped off pyruvate forming acetyl CoA (coenzyme Ais a carrier for acetic acid) • C02 goes to lungs • Energy in acetyl CoA is extracted during aerobic respiration in mitochondria Fig 5.6 5-14

12. Acetyl CoA • Is a common substrate for energy & synthetic pathways Fig 5.12 5-31

13. Krebs Cycle continued Fig 5.8 5-17

14. Krebs Cycle Fig 5.7 • Begins with acetyl CoA combining with oxaloacetic acid to form citric acid • In a series of reactions citric acid converted back to oxaloacetic acid to complete the pathway 5-15

15. Krebs Cycle continued • Produces 1 GTP, 3 NADH, & 1 FADH2 • NADH & FADH2 carry electrons to Electron Transport Chain (ETC) 5-16

16. Electron Transport & Oxidative Phosphorylation • The electron transport chain is a linked series of proteins on the cristae of mitochondria • Proteins are FMN, coenzyme Q, & cytochromes Fig 3.10 5-18

17. Electron Transport & Oxidative Phosphorylation continued • NADH & FADH2 from Krebs carry electrons to ETC • Which are then shuttled in sequence through ETC • NAD & FAD are regenerated to shuttle more electrons from Krebs Cycle to ETC 5-19

18. Electron Transport & Oxidative Phosphorylation continued • As each protein in ETC accepts electrons it is reduced • When it gives electrons to next protein it is oxidized • This process is exergonic • Energy is used to phosphorylate ADP to make ATP • Called oxidative phosphorylation Fig 5.9 5-20

19. Energy Storage • When more energy is taken in than consumed, ATP synthesis is inhibited • Glucose converted into glycogen & fat Fig 5.11 5-30

20. Lactic Acid Pathway • To avoid end-product inhibition, NADHs produced in glycolysis need to give Hs away • In absence of O2, NADH gives its Hs to pyruvate creating lactic acid (anaerobic respiration) • Makes muscles feel fatigued Fig 5.3 5-8

21. Lactic Acid Pathway continued • RCCs don't have mitochondria; use only lactic acid pathway • Occurs in skeletal & heart muscle when oxygen supply falls below critical level • During heavy exercise or vascular blockage 5-9

22. Glycogenesis & Glycogenolysis • For osmotic reasons cells can't store many free glucoses • Instead store glucose as glycogen (glycogenesis) • Skeletal muscle & liver store lots of glycogen • Glycogenolysis clips glucose out of glycogen as glucose 6-phosphate • Phosphate groups trap molecules in cells 5-10

23. Glycogenesis & Glycogenolysis continued • Skeletal muscles use trapped glucose-6-phosphate for own energy needs • Only liver has glucose-6-phosphatase that removes phosphate groups • So glucose can be secreted Fig 5.4 5-11

24. Cori Cycle • Some skeletal muscle lactic acid goes to liver • Where it is converted back through pyruvate to glucose & glycogen • Called gluconeogenesis • Also can happen with amino acids & glycerol Fig 5.5 5-12

25. Chemiosmotic theory Fig 5.10 • Energy gathered by ETC is used to pump H+s into mitochondria outer chamber • Creating high H+ concentration there • As H+s diffuse down concentration & charge gradient thru ATP synthase, & back into inner chamber, their energy drives ATP synthesis (Chemiosmotic theory) 5-21

26. Function of Oxygen Fig 5.10 • Electrons added to beginning of ETC are passed along until reach end • Have to be given away or would stop ETC • O2 accepts these electrons & combines with 4H+s • O2 + 4 e- + 4 H+  2 H20 5-22

27. ATP Formation • ATP can be made 2 ways: • Direct (substrate-level) phosphorylation • Where ATP is generated when bonds break • Both ATPs in glycolysis made this way • 2 ATPs/glucose in Kreb's made this way • Oxidative phosphorylation in Kreb's • Where ATP generated by ETC • 30-32 ATPs made this way 5-23

28. ATP Formation continued • 3H+s pass thru ATP synthase to generate 1 ATP • This yields 36-38 ATPs/glucose • However some of these are used to pump ATPs out of mitochondria • So net yield is 30-32 ATPs/glucose • Really takes 4H+s to generate 1 exported ATP 5-24

29. Production of ATP by ETC • 2.5 ATP produced for each pair of electrons NADH donates • 1.5 ATP produced for each pair of electrons FADH2 donates • Net of 26 ATP produced in ETC 5-25

30. Net Production of ATP • 26 ATP produced in ETC • 2 from glycolysis • 2 from direct phosphorylation in Kreb’s • For total of 30 ATPs for each glucose 5-26

31. 5-27

32. Gluconeogenesis • Occurs when amino acids are converted to Keto acids, then pyruvate, then glucose 5-43