1. Enzymes and Energy

2. Thermodynamics and Biology Metabolism: The totality of an organism’s chemical processes; managing the material and energy resources of the cell Catabolic pathways: degradative process such as cellular respiration; releases energy Anabolic pathways: building process such as protein synthesis; photosynthesis; consumes energy

3. Energy and Enzymes Almost all energy for life is derived from the sun. Life requires energy. Life requires energy The sun is the ultimate source of all energy Energy ~ Capacity to do work Kinetic energy~ energy of motion; Potential energy~ stored energy Chemical energy~ potential energy stored within the bonds of a molecule

4. Thermodynamics~ study of energy flow through living and non-living systems i.e. energy transformations System ~ a process under study in relations to the rest of the universe Closed System~ a system isolated from its environment Open System ~ a system that has relationship with its environment

5. Energy can neither be created, nor destroyed, but can be transformed from one form to another First Law of thermodynamics

6. Free Energy: portion of system’s energy that can perform work e.g. building the molecules in a cell Total Energy = Free Energy + Lost Energy Free Energy < Total Energy

7. Free energy Exergonic reaction: net release of free energy to surroundings Endergonic reaction: absorbs free energy from surroundings

8. Second Laws of Thermodynamics Energy cannot be transformed from one form to another without a loss of useful energy i.e. every energy transformations increases the entropy (disorder, randomness) of the universe A measure of the tendency of a system to become organized is called entropy.

9. The Direction of Spontaneous Reactions (and what it takes to go the other way)

10. Activation energy ~ the initial input of energy to start a chemical reaction Energy and Chemical Reactions Activation Energy

11. Classification of chemical reaction based on whether it releases or uses energy

12. Exothermic Reaction ~ Is accompanied by release of energy Reactants  Products + Energy 10 energy = 8 energy + 2 energy Reactants Products -H-H Energy Energy of reactants Energy of products Reaction Progress

13. C 6 H 12 O 6 +6O 2 →6CO 2 + 6H 2 O + Energy (Useful and waste) An example of exothermic reaction is cellular respiration

14. Endothermic Reaction~ involves an input of energy Energy + Reactants  Products +  H Endothermic Reaction progress Energy Reactants Products Activation Energy

15. 6CO 2 + 6H 2 O + Sun Energy → C 6 H 12 O 6 + 6O 2 An example of endothermic reaction is photosynthesis

16. Enzymes as Catalysts Enzymes ~Catalysts for biological reactions Increase the rate of reactions without being consumed or permanently altered in the process They are mostly proteins and certain class of RNA (ribozymes) Increase the rate of chemical reaction by lowering the activation energy 2.2

17. Enzymes Lower a Reaction’s Activation Energy

18. Effect of Catalyst on Reaction Rate reactants products Energy activation energy for catalyzed reaction Reaction Progress No catalyst Catalyst lowers the activation energy for the reaction.

19. Name of Enzymes Ends in –ase Identifies a reacting substance sucrase- reacts with sucrose lipase reacts with lipid Describes functions of enzyme oxidase -catalyzes oxidation hydrolase - catalyzes hydrolysis

20. Classification of Enzymes ClassReactions catalyzed Oxidoreducataseoxidation-reduction Transferasestransfers group of atoms Hydrolaseshydrolysis Lyasesadd/remove atoms to form a double bonds Isomerasesrearrange atoms Ligasescombine molecules using ATP Table 2.2

21. Mode of Action of Enzymes Substrate: enzyme reactant An enzyme binds a substrate in a region called the active site Active site is a hollow depression (pocket or groove on enzyme) Two main Models Induced fit Model Lock and Key Model

22. Induced Fit Model Enzymes structure flexible, not rigid Enzyme and active site adjust shape to bind substrate Increase range of substrate specificity Shape change also improve catalysis during reaction See Figure 2.5 and 2.6 on page 43 of your textbook

23. Lock and Key Model An enzyme binds a substrate in the active site Only certain substances can fit the active site Amino acid R-groups in the active site help substrate bind Enzyme-substrate complex forms Substrate reacts to form product Product is released The enzyme is available to repeat the cycle

24. Enzymes speed biochemical reactions Figure 4-8: Two models of enzyme binding sites

25. The active site of an enzyme is where substrate is bound. Many Enzymes Work by Altering the Shape of Their Substrates

26. Enzyme Activity-Temperature Low activity at low temp Rate increases with temp Activity lost with denaturation at extreme temperatures

27. Enzyme Activity- pH Maximum activity at optimum pH R group of amino acid have proper charge to interact with the substrate Tertiary structure of enzyme is correct Narrow range of activity Most lose activity in low or high pH

28. Enzyme Activity- Concentration of Substrate Increasing substrate concentration increases the rate of reaction (enzyme concentration is constant) Max activity reached when all of enzyme combines with substrate

29. Enzyme Inhibitors Irreversible (covalent); reversible (weak bonds) Competitive: competes for active site (reversible); mimics the substrate Noncompetitive: bind to another part of enzyme (allosteric site) altering its conformation (shape); poisons, antibiotics

30. Enzyme Inhibitors and Allosteric Regulation A competitive inhibitors Has a structure similar to substrate Occupies the active site Competes with substrate for active site Has effects reversed by increasing substrate concentration

31. A Noncompetitive Inhibitor Does not have a structure like substrate Binds to the enzyme but not active site Change the shape of enzyme and active site Substrate cannot fit altered active site No reaction occurs Effect is not reversed by adding substrate

32. Feedback inhibition Control of Metabolic Pathways

33. ATP and Coupled Reactions

34. Adenosine Triphoshate (ATP) is the energy currency of the cell Cellular respiration converts energy stored in the chemical bonds of food substances into chemical energy stored in ATP ATP is made up of Adenine (nitrogenous base), a ribose sugar (Carbohydrate) and 3 phosphates groups Ribose sugar+ Adenine → Adenosine

35. Adenosine + PO 4 → Adennosine Monophosphate (AMP) AMP is a component of electron carrier and coenzyme NAD + Adenosine +2 PO 4 → Adenosine Diphosphate (ADP)

36. Energy Coupling & ATP Energy coupling: use of exothermic reaction to drive an endothermic reaction Adenosine triphosphate ATP tail: high negative charge ATP hydrolysis: release of free E Phosphorylation (phosphorylated intermediate)~ enzymes

37. ATP - Life’s Energy Currency Energy is released when ATP is hydrolyzed (broken down) to ADP. ATP is restored from ADP and an input of energy. ATP’s energy is used to drive endergonic (energy-requiring) reactions.

38. ATP Chemical work-ATP supplies the energy needed to the macromolecules that comprise the cell Mechanical work- ATP supplies the energy needed to permit muscles to contract, cilia and flagella to beat Transport work- ATP supplies the energy the cells need to pump substances e.g. active transport

39. Enzymes Catalytic proteins: change the rate of reactions w/o being consumed Free E of activation (activation E): the E required to break bonds Substrate: enzyme reactant Active site: pocket or groove on enzyme that binds to substrate Induced fit model