1. I. An Introduction to Metabolism

2. A. The Metabolic Map 1.Metabolism- sum total of all of the chemical reactions in your body a)Metabolism manages the materials and energy resources of the cell. b)Metabolism, aided by enzymes, proceeds step by step along an interrelated pathway 2.Catabolic pathways, such as cellular respiration, break down complex molecules into smaller ones releasing energy 3.Anabolic pathways build up complex molecules from simple ones and require energy from catabolism

3. B. Basic Principles of Energy 1 Energy- the capacity to do work by moving matter against an opposing force A) Kinetic Energy- energy of motion, does work by transferring motion B) Potential Energy- stored energy due to location or arrangement of matter 2. Energy can be changed from one form to another

4. Laws of Thermodynamics 3.First Law of Thermodynamics (Conservation of energy) states that energy can neither be created or destroyed 4.Second Law of Thermodynamics- every time energy changes form, there is an increase of Entropy (S) or disorder. Whenever matter becomes more ordered, its surroundings become more disordered

5. 5.Free Energy- amount of energy that can be put to work under conditions of constant temperature. a)Free Energy (G) is directly related to Total Energy (H) and inversely related to Entropy (S) b)ΔG=ΔH-TΔS (The change in free energy equals the change in total energy minus the absolute temperature times the change in entropy 1)Increased temperature amplifies entropy 2)High energy systems are unstable 3)Highly ordered systems are unstable c) Every spontaneous change in a system proceeds with a decrease in free energy - ΔG

6. C.Chemical Energy and Life 1. Endergonic and Exergonic Reactions A)Exergonic Reactions- occur spontaneously and give off free energy – ΔG. Products G < Reactants G B)Endergonic Reactions- require energy + ΔG 2. In metabolism, exergonic reactions are used to power endergonic reactions 3. As reactions approach equilibrium (ΔG=0) spontaneously, its ability to do work is reduced. The cell must add more free energy.

7. High Energy High Order Low Stability Low Entropy EndergonicEndergonic AnabolicAnabolic Low Energy ExergonicExergonic CatabolicCatabolic Energy in Energy out Low Order High Stability High Entropy

8. D. ATP and Cellular Work 1. Cellular work requires energy a)mechanical work-moving molecules b)transport work- moving substances into and out of the cell c)Chemical work- building polymers

9. 2. The Structure of ATP

10. 3. Function of ATP a.Hydrolysis of the 3 rd phosphate group releases energy b.ATP + H 2 O  ADP + P i ΔG= - 7.3Kcal/mole c.The released phosphate is transferred to another molecule which is then phosphorylated. 4.Phosphorylated molecules are more reactive because they are less stable

11. ATP-ADP Cycle

12. 5. ATP Regeneration: 10,000,000 molecules/second Energy Release Energy Stored Respiration Mitochondrion Glucose + Oxygen + ADP + phosphate ATP + Carbon dioxide 6. The removal of metabolic end products prevents metabolism from reaching equilibrium

13. E.Enzymes- are catalysts, chemical agents that change the rate of chemical reactions without being used up

14. 1. Enzymes lower Activation Energy 2. Activation Energy- free energy needed to start a chemical reactionActivation Energy 3. Example:

15. 4.Before a reaction can occur, the reactants must absorb enough energy to break existing bonds a.Free energy is usually provided as heat b.Many biologically important molecules would decompose if not for high activation energies c.Enzymes allow reactions to occur at body temperature d.Enzymes can only hasten reactions that would occur anyway

16. F. Specificity of Enzymes 1. A particular type of enzyme will only work on a particular substrate producing a particular product –The substrate sucrose is only affected by the enzyme sucrase 2. Enzymes usually take the name of their substrate with an –ase on the end 3. Enzymes bond with a substrate only at a specific region called an active site

17. a)The active site is usually a pocket or a groove on the surface of the protein b) The unique shape of the active site fits the substrate like a lock and a key c) Further, as the substrate enters the active site, the enzyme will usually change shape so the substrate fits more snugly. This is called induced fit.induced fit.

18. Enzyme with empty active sites Substrate (Sucrose) Substrate binds with the enzyme forming an enzyme-substrate complex Hydrolysis occurs Substrate is converted to product and the enzyme is not used up. The enzyme’s active sites are free to accept another substrate molecule G. The Catalytic Cycle of Enzymes

19. G. The Catalytic Cycle 1.Enzymes and substrate are available 2.Enzyme binds to substrate forming an enzyme substrate complex 3.Substrate is converted to product 4.Products are released 5.Since enzymes are not used in the reaction the process repeats.

20. H. Enzymes Mechanisms for Lowering Activation Energy 1.Enzymes provide a template for reactants to orient themselves to facilitate a reaction template 2.Induced fit may stretch critical bonds increasing their ability to be broken 3.Enzymes provide suitable microenvironments for chemical reactions A)Changing pH B)Changing temperature

21. I. Factors Affecting Enzyme Activity

22. 1. Substrate Concentration

23. 2. Temperature

24. 3. pH

25. 4. Enzyme inhibition- some molecules can bind with an enzyme and prevent the enzyme from functioningEnzyme inhibition a)Competitive inhibitor- structurally similar to the substrate. Binds with the active site and reduces enzyme action b)Non-competitive inhibitor- binds to the enzyme away from the active site, disrupting the shape of the enzyme and slowing enzyme action 5. Cofactors- non enzyme helpers for Catalytic Activity. Usually a metal atom. Organic helpers (vitamins) are called coenzymes

26. J. Allosteric RegulationAllosteric Regulation 1.Activators bind to an allosteric site away from the active site, changing the shape of the enzyme to its active form 2.Inhibitors can also bind to an allosteric site, changing the shape of the enzyme to the inactive form activators Inhibitors Inactive form Active form

27. K. Cooperativity- If an enzyme has 2 or more active sites, a substrate molecule attached to one active site can stabilize the enzyme amplifying its response to other substratesCooperativity

28. L. Feedback Inhibition-metabolic pathway in which the reaction is inhibited by its end productFeedback Inhibition