1. Energy and Enzymes How do the right chemical reactions happen in the right place at the right time? A.P. Biology

2. Energy Metabolism Metabolism - All the chemical reactions in a cell Catabolism – breaking reactions Catabolism – breaking reactions Anabolism – making reactions Anabolism – making reactions All chemical reactions need energy All chemical reactions need energy Energy – the ability to do work Energy – the ability to do work Muscle contraction, chemical reactions, intracellular transport, active transport Muscle contraction, chemical reactions, intracellular transport, active transport

3. Types of Energy Kinetic Kinetic Free Energy – energy available to do work Free Energy – energy available to do work Potential Potential Chemical Energy – energy stored in organic molecules Chemical Energy – energy stored in organic molecules

4. Laws of Thermodynamics Law of Conservation of Energy Law of Conservation of Energy Energy is never created or destroyed Energy is never created or destroyed Living things need an energy source Living things need an energy source Law of Entropy Law of Entropy Energy transfer makes the universe more disordered Energy transfer makes the universe more disordered As energy is transferred from chemical to free energy – a lot is lost as heat As energy is transferred from chemical to free energy – a lot is lost as heat Living things need to use a lot of energy to stay ordered Living things need to use a lot of energy to stay ordered

5. Free Energy – energy available to do work G(free/usable energy) = H (total energy) – TS (entropy) G(free/usable energy) = H (total energy) – TS (entropy) Energy converted to heat isn’t available to do work. Energy converted to heat isn’t available to do work. Exergonic – catabolic – breaking – energy releasing Exergonic – catabolic – breaking – energy releasing Endergonic – anabolic – making – energy absorbing – energy is now stored in the molecules made Endergonic – anabolic – making – energy absorbing – energy is now stored in the molecules made

6. Coupling Energy from exergonic reactions are used to power endergonic reactions Energy from exergonic reactions are used to power endergonic reactions Breaking carbs is exergonic – used to make ATP – endergonic (energy stored in ATP) Breaking carbs is exergonic – used to make ATP – endergonic (energy stored in ATP) ATP is broken down to power chemical reactions, muscle contractions, etc. – exothermic ATP is broken down to power chemical reactions, muscle contractions, etc. – exothermic A cell can make 10 million ATP/sec. A cell can make 10 million ATP/sec.

7. Enzymes Enzymes lower the activation energy for a chemical reaction so it can happen with less energy Enzymes lower the activation energy for a chemical reaction so it can happen with less energy One enzyme can convert 1000 molecules/sec. One enzyme can convert 1000 molecules/sec. Enzymes control what chemical reactions happen where and how fast in the body so they generally run the body. Enzymes control what chemical reactions happen where and how fast in the body so they generally run the body.

10. Enzymatic Anabolic Reactions

11. Enzymatic Catabolic Reaction

12. Possible Ways Enzymes Lower The Activation Energy of a Chemical Reaction Bring substrates together and squeezes them (takes less energy to form a bond) - anabolic Bring substrates together and squeezes them (takes less energy to form a bond) - anabolic Substrate binds – changes shape of the enzyme – enzyme squeezes substrate straining the bonds (need less energy to break bonds) - catabolic Substrate binds – changes shape of the enzyme – enzyme squeezes substrate straining the bonds (need less energy to break bonds) - catabolic pH of active site may be highly acidic due to the R groups there (helps break bonds) - catabolic pH of active site may be highly acidic due to the R groups there (helps break bonds) - catabolic Enzyme may actually bond to substrate causing shape changes in the substrate which makes it easier to break the bonds in the substrate Enzyme may actually bond to substrate causing shape changes in the substrate which makes it easier to break the bonds in the substrate

13. Things that Effect Enzyme Rate of Reaction Temperature Temperature At low temperatures, enzymes and substrates move slower – less collisions – slower reaction At low temperatures, enzymes and substrates move slower – less collisions – slower reaction As temperature increases – more collisions – faster rate of reaction until the temp. is too high and the enzyme denatures – rate drops to 0 As temperature increases – more collisions – faster rate of reaction until the temp. is too high and the enzyme denatures – rate drops to 0 pH pH All enzymes work best at an optimal pH, if that pH changes in either direction, enzymes denature All enzymes work best at an optimal pH, if that pH changes in either direction, enzymes denature

14. Things that Effect Enzymatic Rates Enzyme concentration (amt./vol.) Enzyme concentration (amt./vol.) Higher the concentration, faster the rate of reaction Higher the concentration, faster the rate of reaction but even starting with excess substrate, the substrate will run out as enzyme conc. increases the rate will level off but even starting with excess substrate, the substrate will run out as enzyme conc. increases the rate will level off Substrate Concentration Substrate Concentration As sub. conc. increases, act. increases As sub. conc. increases, act. increases Levels off as eventually every enzyme is busy and it can’t go any faster Levels off as eventually every enzyme is busy and it can’t go any faster

15. Things that Effect… Presence of Inhibitors Presence of Inhibitors Competitive Competitive Non-competitive (allosteric) Non-competitive (allosteric) Lab and Artificial Uses of Inhibitors Lab and Artificial Uses of Inhibitors Poisons Poisons Drugs that interfer with enzymes in pathogens (antibiotics) Drugs that interfer with enzymes in pathogens (antibiotics)

16. How the body manipulates enzymes to control chemical reactions Keep a steady amount of Product Keep a steady amount of Product Feedback Inhibition Feedback Inhibition the product of a multi-step pathway allosterically inhibits an earlier step in the pathway the product of a multi-step pathway allosterically inhibits an earlier step in the pathway Substrates turn enzymes on by allosteric activation and products turn off enzymes by allosteric inhibition – (Example: ATP and ADP on a glycolysis enzyme) Substrates turn enzymes on by allosteric activation and products turn off enzymes by allosteric inhibition – (Example: ATP and ADP on a glycolysis enzyme)

18. How the body manipulates enzymes to control chemical reactions Optimize Reactions that must happen efficiently all the time Optimize Reactions that must happen efficiently all the time Spatial Control – some enzymes are embedded in a membrane and cannot move relative to other enzymes – therefore enzymes involved in a step-wise reaction can happen quickly and in order Spatial Control – some enzymes are embedded in a membrane and cannot move relative to other enzymes – therefore enzymes involved in a step-wise reaction can happen quickly and in order Compartmentalization - s ome enzymes are kept in small inside an organelle where reactions can happen more quickly Compartmentalization - s ome enzymes are kept in small inside an organelle where reactions can happen more quickly Can also include keeping the pH and temperature optimal Can also include keeping the pH and temperature optimal

19. How the body optimizes reactions continued Cooperativity Cooperativity used only in multi-subunit enzymes used only in multi-subunit enzymes binding of a substrate causes a conformational change in the enzyme (induced fit) that allows other substrates to bind faster binding of a substrate causes a conformational change in the enzyme (induced fit) that allows other substrates to bind faster more substrate present – faster the enzyme works more substrate present – faster the enzyme works Maximizes reaction with a small amount of substrate Maximizes reaction with a small amount of substrate Coenzymes and Cofactors – necessary in many cases to make the active site the right shape for the substrate Coenzymes and Cofactors – necessary in many cases to make the active site the right shape for the substrate Coenzymes – organic – usually vitamins Coenzymes – organic – usually vitamins Cofactors – inorganic such as Mg, Zn, etc. Cofactors – inorganic such as Mg, Zn, etc. Enzymes can be controlled by the availability of coenyzmes and cofactors Enzymes can be controlled by the availability of coenyzmes and cofactors

20. How the body manipulates enzymes to control chemical reactions Make the Product Only When Needed Make the Product Only When Needed Protein Synthesis – If don’t want to waste energy making enzymes not needed and when needed - not needed fast – can make them from scratch Protein Synthesis – If don’t want to waste energy making enzymes not needed and when needed - not needed fast – can make them from scratch The presence of certain substrates can turn on protein synthesis or products can shut down protein synthesis at the DNA level The presence of certain substrates can turn on protein synthesis or products can shut down protein synthesis at the DNA level A messenger can signal the cell to make enzymes A messenger can signal the cell to make enzymes Compartmentalization - Some enzymes are sequestered and released only at certain times (example amylase and pepsin) Compartmentalization - Some enzymes are sequestered and released only at certain times (example amylase and pepsin)

21. Make the Product Only When Needed Make the Product Only When Needed Cleavage of Enzyme – enzymes are formed in an inactive form and then cleaved when needed to make the right shape (thrombin, pepsin) Cleavage of Enzyme – enzymes are formed in an inactive form and then cleaved when needed to make the right shape (thrombin, pepsin) Phosphorylation – adding phosphates to change the shape and activate or inactivate enzymes Phosphorylation – adding phosphates to change the shape and activate or inactivate enzymes pH –is varied in some organs to control enzyme action – make it the right pH to activate enzymes and the wrong pH to inactivate them (stomach and small intestine) pH –is varied in some organs to control enzyme action – make it the right pH to activate enzymes and the wrong pH to inactivate them (stomach and small intestine)