1. Chapter 6: Energy and Metabolism

2. Biological Work Requires Energy Remember to study the terms Energy Concepts Video

3. Fig. 8-2 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. Diving converts potential energy to kinetic energy. A diver has more potential energy on the platform than in the water.

4. 2 Laws of Thermodynamics 1.) Energy cannot be created or destroyed, but it can be transferred or changed from 1 form to another Photosynthesis: – Sun’s energy  chemical energy in bonds of carbs – Later Chemical energy  cellular work OR mechanical energy

5. 2.) energy is converted from 1 from to another; some usable energy is converted to heat (disperses into surroundings) SO – total amount of energy available to do work is decreasing over time Total amount of energy overall remains constant

6. Fig. 8-3 (a) First law of thermodynamics (b) Second law of thermodynamics Chemical energy Heat CO 2 H2OH2O +

7. Entropy Measure of disorder or randomness Less-usable energy is more disorganized Organized = low entropy Disorganized = high entropy – Ex: heat Entropy – continuously increasing in universe in all natural processes – As more heat is released, our universe becomes more disorganized

8. Enthalpy Total potential energy of the system

9. Free Energy Amount of energy available to do work under the conditions of a biochemical reaction

10. H = G + TS H = enthalpy G = free energy T = absolute temperature in K S = entropy Can’t effectively measure total free energy but can measure CHANGES, so ΔG = ΔH - TΔS

11. Reactions Exergonic – release energy H  L Endergonic – gain energy from surroundings Activation energy – needed to start a reaction Coupled reaction – endergonic + exergonic – exergonic reaction provides energy required to drive endergonic reaction

12. Fig. 8-6 Reactants Energy Free energy Products Amount of energy released (∆G < 0) Progress of the reaction (a) Exergonic reaction: energy released Products Reactants Energy Free energy Amount of energy required (∆G > 0) (b) Endergonic reaction: energy required Progress of the reaction

13. Enzymes – How Enzymes Work VideoHow Enzymes Work Video Enzyme – protein catalyst – Lower activation energy Catalyst – Speed up reaction Substrate – substance that enzyme acts on Enzyme-Substrate complex – – Enzymes orders structure of substrate – Gets reaction going – When breaks  product + original enzyme

14. Enzymes Active site – on enzyme, where substrate binds Induced Fit – substrate binds, changes shape of enzyme – Enzyme and substrate not exactly complementary

15. 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 6 4

16. Enzymes Some – all protein Some – 2 parts – work together to function – 1) protein = apoenzyme – 2) chemical component = cofactor ( C or no C) – Coenzyme – C, nonpolypeptide Binds to apoenzyme as cofactor

17. Enzymes are most Effective At Certain Conditions Temperature – Most – temp increases, reaction rate increases – Low temp = slow – Too high temp. – denatures enzymes pH – enzyme active in narrow range Charge – affect ionic bonds for tertiary and quaternary structure

18. Fig. 8-18 Rate of reaction Optimal temperature for enzyme of thermophilic (heat-tolerant) bacteria Optimal temperature for typical human enzyme (a) Optimal temperature for two enzymes (b) Optimal pH for two enzymes Rate of reaction Optimal pH for pepsin (stomach enzyme) Optimal pH for trypsin (intestinal enzyme) Temperature (ºC) pH 54 3210 678910 0 20 40 80 60100

19. Concentrations of Enzyme and Substrate Lots substrate – enzyme concentration limits Less substrate than enzyme – substrate concentration limits

20. Enzyme Activity Feedback Inhibition – Formation of a product inhibits an earlier reaction in the sequence of reactions – A  B  C  D  E – When E is low – sequence proceeds rapidly – E is high – E1 slows and can stop entire sequence

21. Fig. 8-UN1 Enzyme 1Enzyme 2Enzyme 3 D CB A Reaction 1Reaction 3Reaction 2 Starting molecule Product

22. Allosteric Regulation – Substance binds to enzyme’s allosteric site, changing shape of active site and modifying enzyme’s activity – Allosteric site = receptor site on enzyme, not active site – Allosteric regulators – affect enzyme activity by binding to allosteric sites Keep inactive activate

23. Fig. 8-20 Allosteric enyzme with four subunits Active site (one of four) Regulatory site (one of four) Active form Activator Stabilized active form Oscillation Non- functional active site Inhibitor Inactive form Stabilized inactive form (a) Allosteric activators and inhibitors Substrate Inactive form Stabilized active form (b) Cooperativity: another type of allosteric activation

24. Enzyme Inhibition – can be inhibited or destroyed by certain chemicals Reversible Inhibition – inhibitor forms weak chemical bonds w/ enzyme – Competitive – inhibitor competes w/ normal substrate for active site No permanent damage – Noncompetitive – inhibitor binds w/ enzyme but not at active site e enzymes by altering shape

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

26. Irreversible Inhibition – inhibitor permanently inactivates or destroys an enzyme when it combines w/ enzyme at active site or elsewhere – Ex: poison Mercury, lead, nerve gas, cyanide