Cellular Respiration & Energy: Uses and Storage

1. Chapter 8 Cellular Respiration & Cellular Energy

2. Uses of Energy The ability to do work A) Most energy received by burning of “fuels”. B) Energy released can be converted to other forms. C) Carbon & Hydrogen combine with Oxygen to make Carbon dioxide and Water.

3. 2) Energy from Food (Carbohydrates)are the main source A) Heat released is used to maintain body temperature. B) Rest of energy is conserved in a chemical form. C) Cell Respiration – the slow release of food energy.

4. 3) Food Energy is stored in molecules of ATP A) Adenine – a base found in DNA & RNA. B) Ribose – a 5-carbon sugar found in RNA. C) Adenosine – combination of Adenine + Ribose. D) Phosphate group – (PO4) found in DNA & RNA.

5. E) Cells use similar molecules for different functions. F) AMP – Adenosine Mono- Phosphate. G) Energy is stored in High Energy Phosphate Bonds. H) Energy is transferred when phosphates are removed. I) Phosphorylation – transfer of a phosphate. J) ATP ----> ADP + P + energy

6. 4) Sources of energy for ATP A) Food energy used to add a Phosphate to ADP. B) ATP then used for cellular reactions. C) Glucose supplies most cell energy (1Glucose = 36 ATP) D) Energy is packaged in small, efficient units (ATP).

8. 5) Oxidation-Reduction reactions A) Oxidation – Electrons or Hydrogen atoms removed. B) Reduction – Electrons or Hydrogen atoms gained. C) Redox reactions involve the transfer of energy. D) Oxidation of glucose results in energy release thru the loss of electrons and hydrogen atoms.

9. 6) Hydrogen Acceptors – NAD & FAD A) Biological reactions involve Redox reactions. B) Enzymes require co-enzymes to accept Hydrogen atoms and their electrons. C) NAD – Nicotinamide Adenine Dinucleotide. D) FAD – Flavin Adenine Dinucleotide (Riboflavin).

10. E) NAD + 2H  NADH2 FAD + 2H  FADH2 F) NADH2 & FADH2 are high energy molecules. G) Energy from these are used to make ATP.

11. 7) Types of Respiration • Aerobic – oxygen required. Glucose is completely broken down and maximum amount of energy is released. • Anaerobic – no oxygen used. Glucose is partially broken down and a minimal amount of energy is released. • Phases of respiration: Glycolysis, Kreb’s Cycle, Electron Transport System

13. 8) Glycolysis – splitting of glucose • ATP used as activation energy • Glucose splits into 2 PGAL molecules • PGAL converted into Pyruvic Acid: 2 NADH2 & 2 ATP produced • Net of 2 ATP produced in glycolysis

14. 9) Fermentation • Fermentation is anaerobic respiration. • Glycolysis is followed by the conversion of pyruvic acid into lactic acid in animals & alcohol in plants. • 2 ATP’s and CO2 are produced. • Yeast fermentation used to bake bread.

15. 10) Kreb’s (Citric Acid) Cycle • Completes the break down of glucose. • Pyruvic Acid enters Mitochondria • Pyruvic Acid converted into Acetic Acid • 2 NADH2 & 2 CO2 produced • Enzymes on Cristae complete rest of reaction. • All intermediates are recycled each turn. • Kreb’s cycle produces 4 CO2, 6 NADH2, 2 FADH2 & 2 ATP

16. CO2 NADH2 NADH2 Citric Acid Oxaloacetate CO2 NADH2 FADH2 Alpha-Keto Fumerate CO2 NADH2 ATP

17. 11) Electron Transport System • Electron carriers accept hydrogens from NADH2 & FADH2 and remove energy. • Energy in hydrogens used to make ATP. • Each NADH2 produces 3 ATP’s • Each FADH2 produces 2 ATP’s • 32 ATP’s total produced by the ETS • Oxygen is the final hydrogen acceptor to form water in the last step.

18. Electron Transport • Electron Transport • The electron transport chain uses the high-energy electrons from the Krebs cycle to convert ADP into ATP.

19. Electron Transport • High-energy electrons from NADH and FADH2 are passed along the electron transport chain from one carrier protein to the next.

20. Electron Transport • At the end of the chain, an enzyme combines these electrons with hydrogen ions and oxygen to form water.

21. Electron Transport • As the final electron acceptor of the electron transport chain, oxygen gets rid of the low-energy electrons and hydrogen ions.

22. Electron Transport • When 2 high-energy electrons move down the electron transport chain, their energy is used to move hydrogen ions (H+) across the membrane.

23. Electron Transport • During electron transport, H+ ions build up in the intermembrane space, so it is positively charged.

24. Electron Transport • The other side of the membrane, from which those H+ ions are taken, is now negatively charged.

25. Electron Transport • The inner membranes of the mitochondria contain protein spheres called ATP synthases. ATP synthase

26. Electron Transport • As H+ ions escape through channels into these proteins, the ATP synthase spins. Channel ATP synthase

27. Electron Transport • As it rotates, the enzyme grabs a low-energy ADP, attaching a phosphate, forming high-energy ATP. Channel ATP synthase ATP

28. Electron Transport • On average, each pair of high-energy electrons that moves down the electron transport chain provides enough energy to produce three molecules of ATP from ADP.