Metabolism & Enzymes

1. Metabolism & Enzymes

2. From food webs to the life of a cell energy energy energy

3. Flow of energy through life • Life is built on chemical reactions • transforming energy from one form to another organic moleculesATP & organic molecules sun organic moleculesATP & organic molecules solar energyATP& organic molecules

4. The First Law of Thermodynamics • Energy cannot be created or destroyed, only transformed. • Living systems need to continually acquire and transform energy in order to remain alive. • “Free energy”: The energy available in a system to do work.

5. The Second Law of Thermodynamics • Every time energy is transformed, the entropy (“disorder”) of the universe increases. • In order to increase/maintain their internal order, living systems must process more ordered forms of matter in to less ordered ones

6. Living Systems are “Open” Systems • Matter and energy move in to living systems from the environment. Living systems transform matter and energy and return it to the environment

7. Multi-Step Metabolism • To increase control, living systems produce free energy in multiple-step pathways, mediated by enzyme catalysts

8. Metabolism • Chemical reactions of life • forming bonds between molecules • dehydration synthesis • synthesis • anabolic reactions • breaking bonds between molecules • hydrolysis • digestion • catabolic reactions That’s why they’re calledanabolic steroids!

9. enzyme enzyme + H2O Examples • dehydration synthesis (synthesis) + H2O • hydrolysis (digestion)

10. enzyme enzyme Examples • dehydration synthesis (synthesis) • hydrolysis (digestion)

11. Chemical reactions & energy • Some chemical reactions release energy • exergonic • digesting polymers • hydrolysis = catabolism • Some chemical reactions require input of energy • endergonic • building polymers • dehydration synthesis = anabolism digesting molecules= LESS organization=lower energy state building molecules= MORE organization=higher energy state

12. Endergonic vs. exergonic reactions exergonic endergonic - energy released - digestion • energy invested • synthesis +G -G G = change in free energy = ability to do work

13. Energy & life • Organisms require energy to live • where does that energy come from? • couplingexergonic reactions (releasing energy) with endergonic reactions (needing energy) energy + + digestion synthesis energy + +

14. What drives reactions? • If reactions are “downhill”, why don’t they just happen spontaneously? • because covalent bonds are stable bonds Why don’tstable polymersspontaneouslydigest into theirmonomers? starch

15. energy Activation energy • Breaking down large molecules requires an initial input of energy • activation energy • large biomolecules are stable • must absorb energy to break bonds cellulose CO2 + H2O + heat

16. Too much activation energy for life • Activation energy • amount of energy needed to destabilize the bonds of a molecule • moves the reaction over an “energy hill” Not a match!That’s too much energy to exposeliving cells to! glucose

17. Reducing Activation energy • Catalysts • reducing the amount of energy to start a reaction Pheeew…that takes a lotless energy! uncatalyzed reaction catalyzed reaction NEW activation energy reactant product

18. Catalysts • So what’s a cell got to do to reduce activation energy? • get help! … chemical help… ENZYMES Call in the ENZYMES! G

19. Enzymes • Biological catalysts • proteins (& RNA) • facilitate chemical reactions • increase rate of reaction without being consumed • reduce activation energy • don’t change free energy (G) released or required • required for most biological reactions • highly specific • thousands of different enzymes in cells • control reactionsof life

20. Enzymes vocabulary substrate • reactant which binds to enzyme • enzyme-substrate complex: temporary association product • end result of reaction active site • enzyme’s catalytic site; substrate fits into active site active site products substrate enzyme

21. Properties of enzymes • Reaction specific • each enzyme works with a specific substrate • chemical fit between active site & substrate • H bonds & ionic bonds • Not consumed in reaction • single enzyme molecule can catalyze thousands or more reactions per second • enzymes unaffected by the reaction • Affected by cellular conditions • any condition that affects protein structure • temperature, pH, salinity

22. Naming conventions • Enzymes named for reaction they catalyze • sucrase breaks down sucrose • proteases break down proteins • lipases break down lipids • DNA polymerase builds DNA • adds nucleotides to DNA strand • pepsin breaks down proteins (polypeptides)

23. Lock and Key model • Simplistic model of enzyme action • substrate fits into 3-D structure of enzyme’ active site • H bonds between substrate & enzyme • like “key fits into lock” In biology…Size doesn’t matter…Shape matters!

24. Induced fit model • More accurate model of enzyme action • 3-D structure of enzyme fits substrate • substrate binding cause enzyme to change shape leading to a tighter fit • “conformational change” • bring chemical groups in position to catalyze reaction

25. How does it work? • Variety of mechanisms to lower activation energy & speed up reaction • synthesis • active site orients substrates in correct position for reaction • enzyme brings substrate closer together • digestion • active site binds substrate & puts stress on bonds that must be broken, making it easier to separate molecules

26. Math Skills: Gibbs Free Energy 3.1: All living systems require constant input of free energy Be able to use and interpret the Gibbs Free Energy Equation to determine if a particular process will occur spontaneously or non-spontaneously. • ΔG= change in free energy • (- = exergonic, + = endergonic)  • ΔH= change in enthalpy for the reaction • (- = exothermic, + = endothermic) • T = kelvin temperature • ΔS = change in entropy • (+ = entropy increase, - = entropy decrease)

27. Spontaneity Spontaneous reactions continue once they are initiated. Non-spontaneous reactions require continual input of energy to continue.

28. Using the Equation To use the equation, you’ll need to be given values. • Exothermic reactions that increase entropy are always spontaneous/exergonic • Endothermic reactions that decrease entropy are always non-spontaneous/endergonic. • Other reactions will be spontaneous or not depending on the temperature at which they occur.

29. Sample Problem • Determine which of the following reactions will occur spontaneously at a temperature of 298K, justify your answer mathematically: • Reaction 1: A + B → AB Δ H: +245 KJ/mol Δ S: -.02 KJ / K • Reaction 2: BC→ B + C Δ H: -334 KJ/mol Δ S: +.12 KJ/K

30. Got any Questions?!

31. Factors that Affect Enzymes

32. Factors Affecting Enzyme Function • Enzyme concentration • Substrate concentration • Temperature • pH • Salinity • Activators • Inhibitors catalase

33. Enzyme concentration What’shappening here?! reaction rate enzyme concentration

34. reaction rate enzyme concentration Factors affecting enzyme function • Enzyme concentration • as  enzyme =  reaction rate • more enzymes = more frequently collide with substrate • reaction rate levels off • substrate becomes limiting factor • not all enzyme molecules can find substrate

35. Substrate concentration What’shappening here?! reaction rate substrate concentration

36. reaction rate substrate concentration Factors affecting enzyme function • Substrate concentration • as  substrate =  reaction rate • more substrate = more frequently collide with enzyme • reaction rate levels off • all enzymes have active site engaged • enzyme is saturated • maximum rate of reaction

37. 37° Temperature What’shappening here?! reaction rate temperature

38. Factors affecting enzyme function • Temperature • Optimum T° • greatest number of molecular collisions • human enzymes = 35°- 40°C • body temp = 37°C • Heat: increase beyond optimum T° • increased energy level of molecules disrupts bonds in enzyme & between enzyme & substrate • H, ionic = weak bonds • denaturation = lose 3D shape (3° structure) • Cold: decrease T° • molecules move slower • decrease collisions between enzyme & substrate

39. 37°C 70°C Enzymes and temperature • Different enzymes function in different organisms in different environments hot springbacteria enzyme human enzyme reaction rate temperature (158°F)

40. How do ectotherms do it?

41. Metabolic Strategies • Ectothermy: Conform internal temperature to environmental temperature. • Endothermy: Regulate internal temperature within a narrow range. • Both strategies have advantages and tradeoffs.

42. Body Size Considerations • Smaller animals need to produce more energy per unit of mass due to increased radiation of heat into the environment.

43. Free Energy Considerations & Reproduction • Reproductive strategies are optimized for free energy considerations. • Ex. Seasonal Reproduction.

44. Insufficient Free Energy Production: Individuals • Insufficient free energy production by individuals will lead to disease and death.

45. Insufficient Free Energy Production: Populations • If the individuals in the population are unable to survive, the growth rate of the population will decline

46. Insufficient Free Energy Production: Ecosystems • If the populations in an ecosystem decline, the ecosystems will decrease in complexity

47. Math Skills: Coefficient Q10 3.1: All living systems require constant input • Be able to use and interpret the Coefficient Q10 equation: • t2= higher temperature • t1 = lower temperature • k2= metabolic rate at higher temperature • k1= metabolic rate at lower temperature • Q10 = the factor by which the reaction rate increases when the temperature is raised by ten degrees of free energy

48. Q10 tells us how a particular process will be affected by a 10 degree change in temperature. • Most biological processes have a Q10 value between 2 and 3

49. Sample Problem • Data taken to determine the effect of temperature on the rate of respiration in a goldfish is given in the table below. Calculate the Q10 value for this data. (°C

50. pH What’shappening here?! pepsin trypsin pepsin reaction rate trypsin 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH