Energy

1. Energy An Introduction to Metabolism

2. Metabolism • catabolism - breakdown • anabolism - synthesize

3. Metabolic Pathway • Series of enzymatically catalyzed reactions • examples • Cellular respiration • Photosynthesis http://www.biomedical-engineering-online.com/content/figures/1475-925X-3-15-1-l.jpg

4. Energy • Capacity to do work, to move matter against opposing force • Kinetic Energy (KE) • energy of motion • Potential Energy (PE) • energy of location or structure

5. Energy Transformations • KE --------------------> PE sunlight glucose • PE ----------------------> KE glucose breathing

6. Thermodynamics • The study of energy transformations • Unit of energy = Kcal = 1000 calories • Calorie • Heat required to raise the temperature of 1 g of water 1 °C

7. Laws of Thermodynamics • Laws that govern energy changes • First Law of Thermodynamics • Second Law of Thermodynamics

8. First Law of Thermodynamics • Law of Conservation of Energy • Energy cannot be created or destroyed, only transferred and transformed • quantity is constant, not quality • System • collection of matter under study • Closed - system is isolated from its surroundings • Open - energy can be transferred between the system and surroundings

9. If energy is constant (1st law), why can’t organisms recycle their energy? • Every energy transformation or transfer, some energy becomes unusable (unavailable to do work)

10. Second Law of Thermodynamics • Entropy (S) increases in the universe • ordered forms of energy are partly converted to heat • Energy transformations are not 100% efficient • it is estimated that in 100 billion years all energy will be converted to heat

11. Free Energy • energy available to do work ΔG = ΔH - TΔS Δ means "change in" G = ecosystem H = change in total energy in the system T = temperature (°K)→ °C + 273 S = entropy • It informs us if a process can occur spontaneously • free energy is required for spontaneous change

12. Types of Chemical Reactions • Endergonic reactions • Exergonic reactions

13. G = free energy • G = G final state - G starting state • G < 0 • releases energy • Exergonic reaction • spontaneous • G > 0 • consumes energy • Endergonic reaction • nonspontaneous • G = 0 • reaction at equilibrium

14. Exergonic • reactants products ΔG<O example: cellular respiration C6H12O6 + 6O2 6CO2 + 6H2O ΔG = -686 Kcal/mole Exergonic Releases energy (36-38 ATP)

15. Endergonic • reactants products ΔG>O Example: Photosynthesis ΔG = +686 Kcal/mole Endergonic consumes energy (sun light) 6CO2 + 12H2O C6H12O6 + 6O2 + 6H20

16. Without ATP Class Activity + GLU = NH3 glutamic acid ammonia glutamine • glutamic acid + ammonia glutamine • ΔG = +3.4 Kcal • Is this exergonic or endergonic? • Does it release or consume energy? • Which has greater free energy? (reactants or products) • How many ATP are needed?

17. answers • glutamic acid + ammonia glutamine • ΔG = +3.4 Kcal • Is this exergonic or endergonic? Endergonic, the ΔG is positive • Does it release or consume energy? Consumes • Which has greater free energy? Products (reactants or products) • How many ATP are needed? About half (one ATP requires 7.3 Kcal)

18. Cellular Work • Mechanical work • movement of cell/organelle • Transport work • active transport • Chemical work • synthesis of polymers

19. ATP • Adenosine Tri Phosphate • Adenosine • Adenine • Ribose • 3 phosphate

20. ATP Hydrolysis • In lab conditions (standard conditions) • ΔG = -7.3 kcal/mole • exergonic • ATP + H2O ADP + Pi

21. ATP Synthesis • In lab conditions: • ADP + Pi ATP + H2O • G= +7.3 kcal/mole • endergonic

22. Activation Energy (EA) • Energy required to break existing bonds before forming new bonds • The difference between free energy of the products and the free energy of the reactants is the ΔG. • reactants absorb E to reach the state allowing bond breakage • new bonds form releasing energy A B A B

23. Activation Energy (EA) cont.... • Some require a low EA • Thermal energy provided by room temperature is sufficient to reach the transition state • Most require high EA • Gasoline + oxygen, water evaporation • Heat would speed reactions, but it would also denature proteins and kill cells • Enzymes speed reactions by lowering EA • The transition state can then be reached even at moderate temperatures

24. Catalyst • Chemical agent that accelerates a reaction by reducing the amount of activation energy required • They don’t change the ΔG

25. Enzymes • Class of proteins serving as catalysts • specific • suffix -ase • Catechol oxidase • Sucrase • ATP synthase • Carbonic anhydrase

26. Enzymes (cont.) • CO2 + H2O H2CO3 • without enzyme: 200 = 2 x 102 per hour • with enzyme: 2,000,000,000 = 2 x 109 per hr (carbonic anhydrase)

27. Enzymes are Substrate Specific • Substrate • Active site of enzyme • Induced fit • enzyme-substrate complex

28. Enzymes • A single enzyme molecule can catalyze thousands or more reactions a second • Enzymes are unaffected by the reaction and are reusable • Most metabolic enzymes can catalyze a reaction in both the forward and reverse direction

30. Some Factors that Affect Enzyme Activity • temperature • pH • specificity • cofactor necessity • ionic concentration • substrate concentration

31. 1. Temperature • As T° increases, activity increases BUT • at some point thermal agitation begins to disrupt the weak bonds that stabilize the protein’s active conformation and the protein denatures • each enzyme has an optimal temperature

32. 2. pH • pH also influences shape • each enzyme has an optimal pH • Most enzymes fall between pH 6 - 8

33. 3. Specificity • How discriminating the enzyme is in catalyzing different potential substrates

34. 4. Cofactor Necessity • Some enzymes require a cofactor (nonprotein portion) • they bind to the enzyme permanently or reversibly • Inorganic (cofactor)→ minerals • Organic cofactors (coenzymes) → vitamins, NAD, FAD • The way in which cofactors assist catalysis are diverse

35. 5. Ionic Concentration • Ions interfere with the enzymes ionic bonds • Can disrupt the tertiary level

36. 6. Substrate Concentration • Substrate concentration is directly proportional to the rate until saturation of enzyme is reached

37. ACTIVITY • You are designing an experiment with an enzyme (amylase) that breaks down starch and is present in your small intestine. • What temperature will be the best? • What pH will be the best? • What substrate is the best? • What other factors should you consider?

38. answers • You are designing an experiment with an enzyme (amylase) that breaks down starch and is present in your small intestine. • Temperature: 37°C • pH: 8 • Substrate: Starch • Other factors to consider: cofactors

39. Effectors • Chemicals that regulate enzyme activity • Inhibitors • Activators

40. Inhibitors • Turn enzymes "off" • end product • competitive inhibitor • binds to active site • reversible or permanent • noncompetitive inhibitor • binds to allosteric site • reversible

41. Applications • Pesticides are toxic to insects; Nerve gas toxic to humans inhibit key enzymes in the nervous system • DDT, malathion and parathion inhibit acetylcholinesterase Nerve cells cannot transmit signals, death occurs • Cyanide inhibits enzyme from making ATP • Many antibiotics inhibit enzymes in bacteria Penicillin inhibits an enzyme used in making cell walls • Cancer drugs inhibit enzymes that promote cell division

42. Allosteric Enzymes • Enzymes that exist in active or inactive form • There are 3 forms of regulation • Allosteric activator • Allosteric inhibitor • Cooperativity Active form

43. Allosteric Activator • Binds to allosteric site • stabilize the conformation that has a functional active site • Increases enzyme activity

44. Allosteric Inhibitor (noncompetitive) • Binds to allosteric site • stabilize the conformation that lacks an active site. • Reduces enzyme activity

45. Cooperativity • enzyme w/multiple subunits • Binding of one substrate to active site causes all subunits to assume their active conformation

46. ACTIVITY X A B C Which of these (A, B, C) has a non-competitive inhibitor? What is "X"? What is “Z"? What is “Y”? Z Y

47. answers • C • Substrate • Competitive inhibitor • Enzyme

48. ACTIVITY C B A What type of enzyme is this? What is represented by A? What is the effect of C on the enzyme in this case? Is B an example of stable or inactive?

49. answers • Allosteric • Inactive subunit • Activates the enzyme • Stable

50. Enzyme structure (some) • Types of enzymes • Enzyme: cofactor independent • Holoenzyme: has a permanently bound cofactor • Enzyme + cofactor • Apoenzyme: has a temporary cofactor • Enzyme portion