1. Figure 8.1

2. Fig. 8-1

3. Figure 8.4

4. Chemical Reactions in: Metabolism, Enzymes, ATP AP Biology Chapter 8

5. Quick Write Please write all you know about the following terms/phrases (Limited time) Energy –Potential Energy –Kinetic Energy –Forms of Energy Metabolism –Catabolic reaction –Anabolic reaction Catalyst Enzyme

6. Did you know these terms? Potential energy Kinetic energy Anabolic reaction Catabolic reaction Can you give examples of each?

7. Metabolism All Chemical reactions that occur in biological systems are referred to as metabolism Metabolism include the breaking down { CATABOLISM } and formation of new products { ANABOLISM }

8. Metabolism The net direction of reactions in metabolism (forward or reverse) is determined by the concentration of the [ reactants ] and end [ products ] Chemical equilibrium is when the rate of the forward and reverse reactions are equal…no net production [Sometimes also called ‘dynamic equilibrium’

9. Types of chemical reactions Chemical reactions can be grouped into two categories: –Exergonic Reactions: a spontaneous reaction where there is a net release of energy ( metabolism) –Endergonic Reactions: a nonspontaneous in which free energy is absorbed from the surroundings (photosynthesis)

11. Video clip - energy How about modeling with a rubber band… How is that similar to the bow and arrow example? Law of Conservation of Energy –Is energy ever lost? –Are useable forms of energy lost?

12. Figure 8.2 A diver has more potential energy on the platform than in the water. Diving converts potential energy to kinetic energy. Climbing up converts the kinetic energy of muscle movement to potential energy. A diver has less potential energy in the water than on the platform.

13. Figure 8.5b (a) Gravitational motion (b) Diffusion(c) Chemical reaction

15. Figure 8.7a (a) An isolated hydroelectric system  G  0  G  0

16. Figure 8.7b (b) An open hydroelectric system  G  0

17. Figure 8.7c (c) A multistep open hydroelectric system  G  0

18. ATP Structure

19. ATP ATP (adenosine triphosphate) is a common source of activation energy for metabolic reactions. ATP is an RNA adenine nucleotide with 2 extra phosphate groups. In the process of giving up energy, the last phosphate bond is broken and the ATP is converted to ADP

20. ATP in ACTION … Energy released

21. Phosphorylation New ATP molecules are assembled by phosphorylation, when ADP combines with a phosphate group using energy obtained from a molecule (holding potential E) like glucose. ADP is “phosphorylated” (Phosphate group bonded) and becomes ATP

23. Note model of ATP What are the functional groups to this molecule? What type of biomolecule is ATP? What form of energy is represented in this molecule? Where is the energy stored in a potential state?

25. Scenario examples --- Moving a Piano Childproof cap on medicine bottle

26. Living systems are a series of chemical reactions In order for chemical reactions to take place, the reacting molecules must first collide and then have sufficient energy { ACTIVATION ENERGY } to trigger the formation of new bonds. The presence of a {CATALYST} accelerates (speeds up) the rate of the reaction because it lowers the activation energy needed

27. Video clip

28. Catalyst A catalyst is any substance that accelerates a reaction but does not undergo a chemical change itself. The catalyst can be used over and over again A Biological catalyst is called a(n) _________________

29. ENZYMES A chemical reaction may occur spontaneously if it releases free energy, but lacks control and does not give information about the speed of reaction. Biochemical reactions require ENZYMES to speed up and control reaction rates. An Enzyme is a Biological Catalyst

30. Stages of chemical reactions 1. Activation Energy – Amount of energy that reactant molecules must absorb to start a reaction. This energy is usually provided in the form of heat absorbed by the reactant molecules form the surroundings. 2. Transition State – Unstable condition of reactant molecules that have absorbed sufficient free energy to react. 3. Products are produced

31. P152-153

32. Metabolism & Enzymes Enzymes are the catalyst that activate or accelerate all metabolic reactions by reducing the amount of initial energy (activation energy) required to begin a metabolic reaction. Metabolism is often defined as the process of extracting energy from food taken in and rearranging the food molecules into useable products for your body. (Catabolism + Anabolism = Metabolism)

33. Characteristics of Enzymes: 1.Help speed up a reaction 2. Protein molecules (usually) 3. Specific to the molecules &/or reactions it works on Substrate 4. Reusable – not changed during the reaction 5.Named for its SUBSTRATE. For example, amylase (enzyme) catalyzes the breakdown of amylose/starch (substrate).

34. Enzyme Specificity 1.Enzymes are substrate-specific. For example, amylase cannot breakdown anything but starch –That specificity depends upon the enzyme’s ___________________ 2.Substrate binds to the enzyme’s Active Site –Pocket or grove on the protein’s surface –Formed with only a few amino acids –Shape of enzyme and substrate must match –Changes shape in response to the substrate, also called INDUCED FIT

35. Catalytic Cycle of Enzyme Step 1 Substrate binds to the active site forming an enzyme-substrate complex Step 2 Induced fit of the active site around the substrate; Side chains of a few Amino Acids in the active site catalyze the conversion of the substrate to a product. Step 3 Product departs active site and the enzyme emerges in its original form

36. Remember that the enzyme (blue) is unchanged as a result of a reaction. It can perform its enzymatic function repeatedly.

38. Fig. 8-17 Substrates Enzyme Products are released. Products Substrates are converted to products. Active site can lower E A and speed up a reaction. Substrates held in active site by weak interactions, such as hydrogen bonds and ionic bonds. Substrates enter active site; enzyme changes shape such that its active site enfolds the substrates (induced fit). Active site is available for two new substrate molecules. Enzyme-substrate complex 5 3 2 1 1 6 4 p155

39. Mechanisms used to lower activation energy and speed up reactions 1.Active site can hold two or more reactants in the proper position so they may react 2.Induced fit of the enzyme’s active site may distort the substrate’s chemical bonds, so less thermal energy is needed to break them during the reaction 3. Active site might provide a micro- environment that is conducive to a particular type of reaction (e.g. localized regions of low pH caused by acidic side chains on amino acids at the active site) 4. Side chains of amino acids in the active site may participate directly in the reaction

40. Toothpick-ase Activity Count out 40 toothpicks Repeat for 3 piles of 40… PROCEED with directions

41. Factors affecting Enzyme Efficiency 1.Environmental Conditions a. Temperature The human body is maintained at 98.6  near the optimal temperature for human enzymes Above 104  these enzymes become denatures (they loose their 3D shape) and the hydrogen/peptide bonds begin to break down. b. pH … there is always an optimum pH for each particular enzyme c. Ionic Concentration

43. 2. Initial Substrate Concentration This partly determines the rate of an enzyme controlled reaction. –The higher the substrate concentration, the faster the reaction –If substrate concentration is high enough, the enzyme becomes SATURATED with substrate --- then the reaction rate depends how fast the active sites can convert substrate to product.

44. 3. Enzyme concentration The more enzyme the more reactions can take place

45. 4. Cofactors Cofactors are small nonprotein molecules that assist enzymes for proper catalysis. May bind tightly to active site. May bind loosely to both active site and substrate Some are inorganic --- trace elements such as Fe, Zn, Cu Some are organic and are called coenzymes such as vitamins: ___________ Coenzymes function to donate or accept some component of a reaction (e.g. electrons)

46. Regulating Chemical Reactions How do living systems regulate chemical reactions? How do they know when to start a reaction or end a reaction? One way to regulate a reaction is to regulate its enzyme

47. 5. Enzyme inhibitors Competitive Inhibitors – chemicals that resemble an enzyme’s normal substrate and compete with it for the active site Blocks the active site If reversible, the effect of these inhibitors can be overcome by increased substrate concentration

48. Noncompetitive Inhibitor A non-competitve inhibitor binds to an enzyme at locations other than an active site or allosteric site. The inhibitor changes the shape of the enzyme which disables its enzymatic activity. May act as metabolic poisons (e.g. DDT, many antibiotics)

49. Fig. 8-19 (a) Normal binding (c) Noncompetitive inhibition (b) Competitive inhibition Noncompetitive inhibitor Active site Competitive inhibitor Substrate Enzyme Page 156

50. Allosteric Regulation 6. ALLOSTERIC ENZYMES = have two kinds of binding sites, one active site for the substrate, and an { ALLOSTERIC SITE } for an allosteric effector. There are 2 kinds of allosteric effectors: – Allosteric activator : induces active form of enzyme – Allosteric inhibitor : induces inactive form of enzyme

51. Page 158

52. Modeling an Enzyme Obtain the bag of stuff Use the worksheet to model & identify: –Enzyme –Substrate –Active site –Enzyme – Substrate complex –Allosteric site –Non-competitive inhibitor –Competitive inhibitor

53. Feedback Inhibition One way to regulate a reaction is to allow an end product of a series of reactions to act as an allosteric inhibitor, shutting down the reaction, this is called {FEEDBACK INHIBITION}.

54. The end product acts as an inhibitor, shutting down the reaction.

55. Cooperativity In cooperativity, an enzyme becomes more receptive to additional substrate molecules after one substrate molecule attaches to the active site. This occurs in quaternay structure, when enzymes are composed of multiple subunits (hemoglobin)

56. Fig. 8-20b (b) Cooperativity: another type of allosteric activation Stabilized active form Substrate Inactive form