Ch 5 Energy & Metabolism

1. Ch 5 Energy & Metabolism • Was knocking the tower down difficult? • How much energy did it require? • Was building the tower difficult? • How much energy did it require? • What was needed to rebuild the tower? • Which tower position was more organized? • Would the tower ever break if no one knocked it down? Now… pretend the tower is a macromolecule, say protein, in your body… • Is breaking a protein difficult? • How much E does it take? • Is building a protein molecule difficult? • How much E does it take? • What is needed to build a protein molecule? • Which protein position is more organized, built or broken?

2. Metabolism Cell is chem factory Metabolic pathways catalase H2O2 H2O + O2 2 general types of pathways…

3. Catabolic downhill Breaks molecules Gives off E Free E decreases (-G) Exergonic Occurs spontaneously Entropy increases (+S) Ex: cell respiration, breakdown of H2O2 by catalase Anabolic uphill Builds molecules Absorbs E Free E increases (+G) Endergonic Occurs nonspontaneously Entropy decreases (-S) Ex: photosynthesis, synthesis of H2O2 Comparing catabolic & anabolic rx

4. Catabolic Vs. Anabolic rx

5. Energy E – capacity to do work • Kinds: • Kinetic – motion • Potential – stored; capacity to do work • Heat – type of kinetic; assoc. w/ movement of molecules. Most random kind of E.

6. Chemical Energy Molecules in living cells have pot E. b/c of the arrangement of their atoms. The E is stored in the covalent bonds.

7. THERMODYNAMICS: the SCIENCE of ENERGY TRANSFORMATIONS 1st Law of Thermodynamics • E can neither be created nor destroyed • Aka: Conservation Of Energy 2nd law of Thermodynamics • Entropy of the universe is increasing • systems tend to becomes more disorganized as time goes on

8. Shows transformation of energy nicely http://media.pearsoncmg.com/bc/bc_campbell_biology_7/media/interactivemedia/activities/load.html?8&A

9. The quantity of E in universe is constant, but the quality is not On a larger scale, energy flows into the ecosystem in the form of light & leaves in the form of heat.

10. Orgs live at the expense of free E Free E – the portion of a system’s E that is available to do work • G – free E • H – total E • S – entropy • Systems rich in free E are unstable • As rx proceeds towards equilibrium G of the rx decreases • A rx @ equilibrium performs no work; G=0 • As rx is pushed away from equilibrium G of the rx increases

11. Energy Coupling • Using an exergonic process to drive an endergonic. • ATP drives by coupling • Structure of ATP • http://media.pearsoncmg.com/bc/bc_campbell_biology_7/media/interactivemedia/activities/load.html?8&B

12. Shows catabolic vs anabolic rx & energy coupling http://media.pearsoncmg.com/bc/bc_campbell_biology_7/media/interactivemedia/activities/load.html?8&C

13. Phosphorylated Intermediate The molecule w/ the inorganic phosphate, from an ATP molecule, attached to it which is very unstable & therefore more reactive.

14. Regeneration of ATP

15. One of 2 ways to synthesize ATP

16. Enzyme • Catalytic protein • Speed up metabolic rx by lowering energy barriers • Not consumed by rx • selective

17. Activation E Initial investment of E required to break bonds

18. Activation E w/ vs. w/out Enzyme

19. More on Enzymes Substrate – reactant the enzyme works on Active site – catalytic center Induced fit – enzyme / substrate complex changes shape slightly so the active site fits even more snugly around substrate How do they lower activation E? • Cause reactants to come close together • Active site provides a microenvironment for rx (acidic side groups…)

21. Denature • Each enzyme has optimal temp & pH • Ex: pepsin – pH 2

22. Each enzyme has optimal temp & pH

23. Cofactors • Inorganic molecule or ion required for the proper functioning of the enzyme • Can be bound to active site or to substrate • Ex: Zn, Fe, Cu • Coenzyme – an organic cofactor. Most are vitamins

24. Enzyme inhibitors • Selectively disrupt action of enzyme either reversibly or irreversibly • 2 types • Competitive inhibitors – • Noncompetitive inhibitors –

25. Control of Metabolism Inhibition & activation of enzymes by molecules are essential to metabolic control • Allosteric enzyme – oscillates b/t 2 conf. states – active & inactive • allosteric site – receptor site separate from active site

26. Control of Metabolism Activator molecule binds to active site – activates enzyme Inhibitor molecule binds to allosteric site – inhibits enzyme b/c no active site available

27. Cooperativity • Occurs when the induced fit binding of substrate to active site changes the conformation such that all active sites are more active.

28. Metabolic order emerges from the cell’s regulatory systems & structural organization • Metabolic pathways get switched on & off. • How? Feedback inhibition – occurs when a metabolic pathway is switched off by its end product which acts as an inhibitor of an enzyme along the pathway

29. Structural order & metabolism • Complex cell structure orders met pathways in space & time • Product from the first enzyme becomes substrate for the next in the pathway • Each organelle has its own chem env & special blend of enzymes

31. Link to a 10 question interactive quiz http://www.dwm.ks.edu.tw/bio/activelearner/06/ch6quiz.html