1. ENERGY Laws of Thermodynamics (1st/2nd) Free energy diagrams- activation energy, exothermic, endothermic Metabolism- anabolic/catabolic ENZYMES Induced fit model, lock & key Effect on activation energy Temperature, pH, Cofactors/Coenzymes, Enzyme/Substrate Concentration Inhibition, Allosteric Regulation Topics covered for the Quiz Friday

2. Time to sing

3. Feedback Inhibition Controlling Enzyme Function Cont’d

4. Enzymes Work Together Enzyme facilitates change of reactants  products then passed on to another enzyme Final desired product forms after series of reactions Processes are reversible and depend on the concentrations off substances available A B C D A forms B, now there is less A and B is used up for C, etc. Cycle starts pulling to the right, making more D E1E2E3 Overall force towards product D

5. When surrounding factors of the reaction are constant (pH, temperature), the enzyme production/activity is proportional to either the [Substrate] or the [Product ] FEEDBACK INHIBITION Enzyme regulation in which the formation of a product inhibits an earlier reaction in the sequence A B C D As the [D] increases, a signal is sent to E1 to say STOP ****When enough product is present, it turns itself off E1E2E3

6. Feedback Inhibition A way to self- regulate

7. How does a product inhibit an enzyme? Binds to the regulator site (inhibitor site) on enzyme near the beginning of the pathway Allosteric change- enzyme can’t bind onto its substrate All subsequent reactions are turned OFF -- the metabolic pathway is effectively halted

8. As end product is used up or removed ([product] decreased to a critical level), the inhibitor will fall off the first enzyme A B C D Reaction proceeds  the [product] is always controlled within a certain range E1E2E3 E1E2E3 The hallmark of all the reversible inhibitors is that when the inhibitor concentration drops, enzyme activity is regenerated

9. Allosteric regulation of the GLYCOLYTIC PATHWAY The oxidation of glucose providing energy in the cell Catabolic pathway- consumes glucose; produces ATP, NADH, and pyruvate Early reaction in the pathway catalyzed by phosphofructokinase-1 (PFK1)  Key step for the regulation of glycolysis When ATP levels rise, ATP binds an allosteric site in PFK1 to decrease the rate of the enzyme reaction; glycolysis is inhibited and ATP production falls *Negative feedback helping maintain a steady concentration of ATP in the cell Glucose (fructose-6-phosphate) PFK1 (fructose-1,6-bisphosphate) ATP NADH Pyruvate Figure: feedback inhibition in glycolysis Example of Feedback Inhibition in our Cells

10. http://highered.mcgraw- hill.com/sites/0035456775/student_view0/chapter6/feedb ack_inhibition_of_biochemical_pathways.html