Microfilaments differ from microtubules in that microfilaments

1. Microfilaments differ from microtubules in that microfilaments A) are larger than microtubules.   B) are found only in plants whereas microtubules are found in plants and animal cells.   C) are mainly composed of actin whereas microtubules are composed of tubulin.   D) anchor organelles, whereas microtubules primarily function to help cells change shape and move.   E) form the inner core of cilia and flagella whereas microtubules regulate metabolism.

2. Cellular Energetics: Thermodynamics, ATP, and Enzyme catalysis Campbell Biology Chapter 5

3. Energy and Thermodynamics

4. Energy is the capacity to do work • There are many forms of energy: • Kinetic energy • Potential energy • Chemical energy • Electrical energy

5. All Living Things Require and Consume Energy • We get our energy from food • Ultimate source of energy for all life on earth is the sun

6. The First Law of Thermodynamics • Energy cannot be created or destroyed • The amount of energy in the universe is constant • Energy can be interconverted from one form to another: • Potential energy • Kinetic energy • Radiant energy

7. Potential energy • Energy is the ability to do work • Potential Energy of position • Gravitational potential energy • Chemical potential energy

8. Kinetic energy • Energy of motion • KE= 1/2mv2 • Temperature is a measure of molecular kinetic energy

9. The 1st Law of Thermodynamics: Energy can be interconverted from one form to another

10. More energy interconversions

11. The 2nd Law of Thermodynamics : The Law of Entropy • Interconversions of energy are never 100% efficient • Entropy! • Entropy is a measure of disorder (i.e. chaos, randomness) • Each interconversion of energy involves loss of usable energy

12. Entropy in Action

13. Biochemical reactions are inefficient

14. The price of minimizing entropy is the constant expenditure of free energy

15. Closed systems will deplete themselves of usable (free) energy • Given a finite amount of energy, each energy interconversion will result in an ever-increasing amount of unusable energy (entropy)

16. Recognizing Entropy in the world

17. Which system has more entropy? A B

18. Can living systems reduce entropy?

19. Recognizing Enthalpy B Enthalpy = Energy in chemical bonds

20. Which systems have more Enthalpy? Or these?  These? 

21. Biochemical reactions are spontaneous only if ∆G is negative • Reactions which release energy are exergonic • Reactions which require energy are endergonic ∆ G = ∆H - T∆S • Only exergonic processes with a negative ∆G are spontaneous • Spontaneous processes can be harnessed to perform work

22. If ΔG < 0, the reaction is spontaneous (it will happen) C6H12O6(s) + 6O2(g) 6CO2(g)+ 6H2O(l) Will the Reaction happen? Well, is heat given off? Does entropy increase? G = ∆H - T∆S ∆H = enthalpy (heat in chemical bonds) ∆S= Degree of entropy (chaos) created by Rxn T= Temperature at which Rxn occurs Important: Spontanous ≠ fast

23. Heat LE 5-2b Chemical reactions Carbon dioxide Glucose ATP ATP Water Oxygen Energy for cellular work

24. Which of these diagrams depicts an endergonic reaction? Reactants Products Amount of energy required Amount of energy released Energy required Energy released Potential energy of molecules Potential energy of molecules Reactants Products A B

25. G < 0 G = 0 LE 8-7a A closed hydroelectric system

26. G < 0 G < 0 LE 8-7c G < 0 A multistep open hydroelectric system

27. In living things, a state of equilibrium most often means ___________. • Efficiency is optimized • The reaction is Endothermic • Enthalpy is increased • Entropy is minimized • You are dead

28. ATP

29. A steer must eat over 100 pounds of grain to gain less than 10 pounds of muscle tissue. This illustrates A) the first law of thermodynamics.   B) the second law of thermodynamics.   C) that some energy is destroyed in every energy conversion.   D) that energy transformations are typically 100% efficient.   E) None of the choices are correct.

30. Living cells manage to perform endergonic activities • How is this possible?

31. ATP hydrolysis can be coupled to endergonic reactions to power cellular work • A cell does three main kinds of work: • Mechanical • Transport • Chemical • To do work, cells manage energy resources by energy coupling, the use of an exergonic process to drive an endergonic one

32. The Structure and Hydrolysis of ATP • ATP (adenosine triphosphate) is the cell’s energy shuttle • ATP provides energy for cellular functions • ATP is a nucleic acid monomer

33. Adenine ATP is the energy currency of all living things Phosphate groups Ribose ATP: Adenosine Triphosphate

34. P P P LE 8-9 Adenosine triphosphate (ATP) H2O + P P P + Energy i Adenosine diphosphate (ADP) Inorganic phosphate

35. Phosphorylation can change the conformation of proteins

36. Anabolic (building up) reactions are usually endergonic NH2 NH3 DG = +3.4 kcal/mol + Glu Glu LE 8-10 Ammonia Glutamine Glutamic acid Breakdown of ATP is exergonic P ATP ADP DG = –7.3 kcal/mol H2O + + i Coupled reactions: Overall DG is negative; together, reactions are spontaneous DG = –3.9 kcal/mol

37. How ATP Performs Work • ATP drives endergonic reactions by phosphorylation, transferring a phosphate group to some other molecule, such as a reactant • The recipient molecule is now phosphorylated

38. Three types of cellular work are powered by ATP hydrolysis • Mechanical • Transport • Chemical

39. The Regeneration of ATP • ATP is regenerated by addition of a phosphate group to ADP • The energy to phosphorylate ADP comes from food • The chemical potential energy temporarily stored in ATP drives most cellular work

40. ATP LE 8-12 Energy for cellular work (endergonic, energy- consuming processes) Energy from catabolism (exergonic, energy- yielding processes) P ADP + i

41. Enzymes

42. At which level of protein structure are interactions between R groups most important? A) primary B) secondary C) tertiary D) quaternary E) the R groups are not related to the overall structure of a protein

43. Sugar is an energy-rich molecule • Breakdown of sugar is spontaneous • C6H12O6(s) + 6O2(g) 6CO2(g)+ 6H2O(l)

44. Wood and paper are made of cellulose • Cellulose is a polymer of glucose • Why doesn’t our jar of sugar burst into flame?

45. Exergonic reactions still require activation energy • Spontaneous ≠ fast • Ea is dependent on temperature • At high temperatures, reactions happen faster

46. Jumping bean analogy • Molecules are like jumping beans • Temperature ≈ height of jump • Living things cannot wait for a good jump • After a long time, where will the beans be? • All of them? • Will they ever stop jumping?

47. Living things can use enzymes to speed up reactions • Enzymes speed up reactions by lowering energy of activation • They are catalysts

48. Catalysts speed up reactions • Platinum is used in catalytic converters • 2CO + 02 2CO2 • Catalysts are not consumed in a reaction • They cannot add energy to a reaction

49. Enzymes are protein catalysts Catalase • Catalysts- things added to chemical reactions which speed up those reactions • Catalysts are not consumed in a reaction • Catalysts cannot add energy to a reaction • -ase: The enzyme suffix

50. Enzymes can dramatically lower the energy of activation for a reaction no enzyme with enzyme E a E Energy a reactants products Reaction Course Note that the equilibrium of the reaction is unaffected 12