Lecture 5 Outline (Ch. 8)

2. Lecture 5 Outline (Ch. 8) • I. Energy and Metabolism • II. Thermodynamics • A. 1st Law – conservation of energy • B. 2nd Law - entropy • Free Energy • Chemical Reactions • V. Cellular Energy - ATP • VI. Enzymes • A. Function • B. Regulation • VII. Lecture Concepts

3. Energy What is Energy? The capacity to cause change Types of Energy: - thermal - Kinetic Energy = energy of movement - Potential = stored energy - chemical

4. Metabolism Metabolism – all the chemical conversions in an organism

5. Thermodynamics Potential Energy Kinetic Energy Thermodynamics – study of energy transformation in a system Potential energy can be converted to kinetic energy (& vice versa)

6. Thermodynamics Laws of Thermodynamics: Explain the characteristics of energy • 1st Law: • Energy is conserved • Energy is not created or destroyed • Energy can be converted (Chemical  Heat) 2nd Law: • During conversions, amount of useful energy decreases • No process is 100% efficient • Entropy (measure of disorder) is increased Energy is converted from moreuseful to less useful forms

7. Metabolism • Metabolic reactions: • Chemical reactions in organism Two Types of Metabolic Reactions: • Anabolic = builds up molecules Catabolic = breaks down molecules

8. Free Energy + + Reactants Products • Chemical Reaction: • Process that makes and breaks chemical bonds • Two Types of Chemical Reactions: • 1) Exergonic = releases energy • 2) Endergonic = requires energy

9. Free Energy Energy of a system • Gibb’s free energy = energy available to cause change - predict if rxn will occur • difference in free energy (ΔG) • system – moves to more stable (lower energy) • If ΔG (-), -release energy -process spontaneous • If ΔG (+) or 0, -consume energy -process non-spontaneous

10. Chemical Reactions Glucose  CO2 + H20 CO2 + H20 Glucose -ΔG +ΔG (or 0) release free energy intake free energy spontaneous non-spontaneous • Exergonic reaction • Endergonic reaction

11. Chemical Reactions • Chemical Reactions: • Like home offices – tend toward disorder

12. Chemical Reactions • Chemical Reactions: • Endergonic – energy required to complete reaction • Exergonic – energy given off Exergonic Endergonic

13. Chemical Reactions • 1. Exergonic reactions: “Energy out” • Reactants have more energy than products • Reaction releases energy • 2. Endergonic reactions: “Energy in” • Products have more energy than reactants • Requires influx of energy »

14. Chemical Reactions Nucleus Nucleus Repel Activation Energy Activation Energy Nucleus Nucleus Repel Activation Energy: Energy required to “jumpstart” a chemical reaction • Must overcome repulsion of molecules due to negative • charged electrons

15. Chemical Reactions “Downhill” reactions Exergonic Reaction: • Reactants have more energy than products But will sugar spontaneously burst into flames? Activation energy: Make sugar and O2 molecules collide sugar + O2 water + CO2

16. Cellular Energy - ATP • ATP = adenosine triphosphate • ribose, adenine, 3 phosphates • last (terminal) phosphate - removable

17. ATP + H2O ADP + Pi Cellular Energy - ATP • ATP hydrolyzed to ADP • Exergonic • ΔG = -7.3 kcal/mol • Energy released, coupled to another rxn (endergonic)

18. Cellular Energy - ATP endergonic exergonic • by coupling, overall rxn still exergonic

19. Cellular Energy - ATP • ATP regenerated • ΔG = +7.3 kcal/mol • cells power ATP generation by coupling to exergonic rxns - cellular respiration

20. Enzymes • Enzymes – rate of chemical rxn • sucrase – enzyme sucrose breakdown “-ase” enzyme • sucrase – catalyst -speed up rxn, not consumed -contort molecule • break bonds reactants • form bonds products -unstable -energy given off -need energy input

21. Enzymes • energy input Energy of activation (EA) • reactants – absorb energy - EA • EA from heat • rxn proceeds Exergonic – energy given off • rxn rate – due to reaching EA • EA from ambient heat? - usually insufficient • This is GOOD!

22. -don’t make endergonic exergonic Enzymes Enzymes • lower EA • only for specific rxns • cell chooses which rxns go forward • This is GOOD! enzymes: -don’t change ΔG -do speed up rxn would occur anyway

23. Enzymes • enzyme – specific to substrate • active site – part of enzyme -substrate • binding tightens fit – induced fit • form enzyme-substrate complex • catalytic part of enzyme: converts reactant(s) to product(s)

24. Enzymes • Enzymes lowers EA by: -template orientation -stress bonds • substrate(s) enter -microenvironment • enzyme reused • products formed • Enzyme activity affected by: substrate conc., temp., pH

25. Enzymes normal • inhibitors: competitive – bind active site non-competitive – binds other site – alters conformation competitive inhibition • Drug – blocks HIV enzyme - competitive inhibition non-competitive inhibition

26. Enzymes Room is cold Feedback Inhibition: Like your furnace: warmer warmer Room is warm Detector activated Heat kicks on Heat stays on

27. Self-Check

28. Lecture 5 concepts • Define metabolism, thermodynamics, free energy • Describe the 1st and 2nd laws of thermodynamics and how they relate to chemical reactions • Explain the terms exergonic and endergonic in terms of free energy and chemical reactions • Draw a graph of free energy for exothermic and endothermic chemical reactions; label products, reactants, & EA • Discuss the structure and purpose of ATP • Draw and describe how enzymes affect chemical reactions • List factors that affect enzyme activity • Write out a list of new terminology and provide descriptions