Energy and the Underlying Organization of Life

1. Metabolism Cell’s capacity to Acquire energy Build-anabolism Break apart-catabolism Release substances Defining Energy Potential Energy-energy of position Kinetic Energy-energy of motion Heat (Thermal) Energy-usually a waste product Chemical Energy-energy for work (like carbs) Kilocalories Energy and the Underlying Organization of Life

2. Total Energy Content • Energy content of any system with the environment remains constant-neither created or destroyed

3. How Much Energy is Available? • First Law of Thermodynamics • Energy cannot be created or destroyed • Second Law of Thermodynamics • Total amount of energy in the universe is flowing from higher to lower quality • Entropy • System’s disorder • This is constantly increasing in the universe

4. One-Way Flow of Energy Flow of energy into life and one-way flow of energy out of it

5. Doing Cellular Work Mechanical Work Energy input required Potential energy released by downhill run

6. Doing Cellular Work • Reactions • Endergonic-energy used • Exergonic-energy released • Cells couple energy to get the job done

7. ATP The Cell’s Energy Currency • ATP - Adenosine Triphosphate • Ribose • Adenine • Three phosphate groups • Phosphorylation-helps to supply energy

8. ATP and Cellular WorkA Calcium Pump Phosphorylation

9. Electron Transfers • Oxidation-reduction reactions • Donating and acceptance of electrons • Conservation of energy

10. Metabolic Pathways • Ordered • Enzyme-mediated • Biosynthetic or Degradative

11. Enzyme Structure and Function • Catalysts speed the rate of chemical reactions • Not permanently altered or used up • Reversible reactions • Selective for the substrates

12. Enzyme Activation Energy

13. Enzyme Substrate Interaction Reaction rate is enhanced by lowering the activation energy

14. Model of Enzyme at Work Glucose in site - Reaction takes place Active site exposed

15. Induced-Fit Model of Enzyme-Substrate Interactions

16. Four Features of Enzymes • Helping substrates get together • Orienting substrates in positions favoring reactions • Promoting acid-base reactions • Shutting out water

17. Factors Influencing Enzyme Activity • Temperature • pH • Salinity • Ranges are specific Heat sensitive enzyme controls melanin production

18. Control of Enzyme Function • Allosteric control • Binding of substances on enzyme other than the active site • Can activate • Can inhibit

19. Feedback Inhibition • Shutting down of activity • Product produced shuts down reaction

20. Reactants, Products, and Cell Membranes • Selective permeability • Small non-polar molecules pass easily • Some molecules need transport proteins • Bulk movement • Exocytosis - out of cell • Endocytosis - into cell

21. Concentration Gradients • Diffusion • Passive transport • Transport proteins • Movement occurs both ways across membrane • Active transport • Uses ATP

22. Diffusion

23. Passive Transport

24. Active Transport

25. Movement of Water Across Membranes • Osmosis- diffusion of water • Tonicity • Hypotonic- more solvent than solute • Hypertonic- more solute than solvent • Isotonic- equal solvent/solute • Fluid pressure • Hydrostatic pressure- water pressure keeps earthworms plump

26. Osmosis and Solute Concentration

27. Effects of Tonicity

28. Effects of Fluid Pressure

29. Loss of Fluid Pressure Plasmolysis - Plasma membrane moves away from the wall

30. Exocytosis and Endocytosis Large molecules or particles

31. Receptor-Mediated Endocytosis Receptor proteins bind solutes

32. Phagocytosis Amoebas and macrophages engulf their targets

33. In Conclusion • The sum of metabolism underlies the survival of organisms • The First and Second Laws of Thermodynamics affect life • Energy can be converted from one form to another but cannot be destroyed • Energy flows from higher to lower quality

34. In Conclusion • All matter has some form of potential energy which can be converted to kinetic energy • Cells stay organized as long as they balance energy expenditures with energy replacements • Metabolic reactions can release or require energy

35. In Conclusion • Exergonic reactions end with a net loss of energy • Endergonic reactions end with a net gain of energy • Cells couple exergonic and endergonic reactions • ATP is the main energy carrier in cells

36. In Conclusion • ATP forms when a phosphate is donated to ADP • Transfer of electrons from one substrate to another involves ATP • Metabolic pathways are orderly, stepwise sequences of enzyme-mediated reactions • Enzymes are catalysts, lower activation energy, and bind substrates

37. In Conclusion • Enzymes are temperature, pH, and salinity specific • Molecules or ions diffuse down a concentration gradient • Some molecules diffuse across the membrane • Transport mechanisms involve passive and active transports

38. In Conclusion • Osmosis is the diffusion water across a selectively permeable membrane • Different tonicities influence the movement of water • Cells acquire or get rid of substances in bulk by exocytosis and endocytosis • developed by M. Roig