1. 2.5 - Enzymes

2. Catalysts – speed up reactions without being used up or changed by the reaction

3. A. Activation energy – amount of energy needed to get a reaction started

4. B. Catalysts work by lowering the activation energy

5. Enzymes – Biological catalysts
A. Proteins – very specific shapes
B. Usually end in –ase

6. C. Substrate – reactants in an enzyme- catalyzed reaction D
C. Substrate – reactants in an enzyme- catalyzed reaction D. Active site – spot on enzyme where substrate binds ****Remember – VERY specific!!!***

7. How enzymes work
A. Lower activation energy by positioning substrates in a way that is favorable to reacting
1. Substrate must enter active site with minimum rate of motion necessary for reaction to occur (enzyme provides NO energy!)

8. B. Substrate joins
with enzyme at active
site to form
enzyme-substrate
complex
Product(s) released,
enzyme unchanged and
free to catalyze the
reaction again with new
set of reactants

9. Induced fit model – enzyme undergoes change in conformation as it interacts with substrate

10. Factors that affect enzyme activity
A. Temperature
1. As temperature increases, molecules move faster, collide more often and with more energy

11. 2. Enzymes have an ideal temperature a
2. Enzymes have an ideal temperature a. Too cold – molecular motion too slow b. Too hot – enzyme loses shape

12. pH - proportion of H+ and OH- ions
1. H+ and OH- ions can bind with enzyme or substrate and influence bonding between the two

13. Substrate Concentration
1. As substrate concentration increases, enzyme activity increases until a maximum rate is achieved

14. Inhibition
A. Competitive Inhibition – a molecule binds into the active site, blocking access to the substrate
1. Can be reversible or irreversible
2. If reversible, can be overcome by increasing substrate concentration

15. Non-competitive Inhibitors – bind elsewhere on enzyme and forces change in shape of active site
1. Also called allosteric inhibition
2. Can be reversible or irreversible

16. End-Product Inhibition
1. Metabolic pathways – most metabolic functions in the body are actually a series of reactions
2. Final product acts as an allosteric inhibitor to the first enzyme in the series