Energy and Metabolism

1. Energy and Metabolism

2. Energy • Capacity to do work, which is any change in the state or motion of matter • Measured as heat energy • Unit of measure is the kilocalorie (kcal)

3. Potential energy • Capacity to do work owing to position or state • Chemical energy is potential energy stored in chemical bonds • Kinetic energy • Energy of motion

4. Closed system does not exchange energy with its surroundings • Organisms are open systems

5. Closedandopensystems

6. First law of Thermodynamics • Energy cannot be created or destroyed • Energy can be transferred and changed in form • Organisms cannot produce energy, but as open systems, they can capture it

7. Second law of Thermodynamics • Entropy is continuously increasing • No energy transfer is 100% efficient • Some energy is dissipated as heat • Organisms maintain their organization only with input of energy from surroundings

8. Metabolism • Sum of all the chemical activities taking place in an organism • Anabolism • Complex molecules synthesized from simpler substances • Catabolism • Larger molecules broken down into smaller ones

9. Enthalpy is total potential energy of a system • As entropy increases, amount of free energy decreases • H = G + TS • H is enthalpy • G is free energy • S is entropy • T is absolute temperature in degrees Kelvin

10. Exergonic reaction • Releases energy that can perform work • In coupled reaction, supplies input of free energy to drive an endergonic reaction • Endergonic reaction increases free energy

11. Exergonic and endergonic reactions

12. Dynamic equilibrium • In a chemical reaction, rate of change in one direction is the same as in the opposite direction • When concentration of reactant molecules increases, the reaction shifts until equilibrium is re-established

13. Adenosine triphosphate (ATP) • Holds readily available energy for very short periods • Donates energy by means of terminal phosphate group • Common link between • Exergonic and endergonic reactions • Catabolism and anabolism

14. ATP and ADP

15. ATP linksexergonicand endergonic reactions

16. Redox reactions • Substance that becomes oxidized gives up energy • Substance that becomes reduced receives energy • Essential part of cellular respiration, photosynthesis, and other chemical reactions

17. NAD

18. Enzymes • Biological catalysts • Cells regulate the rate of chemical reactions with enzymes • Lower activation energy (energy required to break existing bonds) • Although most enzymes are proteins, some types of RNA molecules have catalytic activity as well

19. Enzymes • Work best at specific temperature and pH conditions • Catalyze virtually every chemical reaction that takes place in an organism • Some enzymes consist only of protein • Some enzymes have two components • Protein called apoenzyme • Cofactor

20. Important classes of enzymes [insert table 6-1 when available]

21. Feedback inhibition • Formation of an end product inhibits an earlier reaction in the metabolic pathway

22. Feedbackinhibition

23. Reversible inhibition • Competitive inhibition • Inhibitor competes for the substrate for the active site • Noncompetitive inhibition • Inhibitor binds with enzyme at a site other than active site • Irreversible inhibition • Inhibitor combines with an enzyme and permanently inactivates it

24. Competitive and noncompetitive inhibition