1. Enzymes

2. What Are Enzymes? Most enzymes are proteins
Act as catalysts to accelerate a reaction
Not permanently changed in the process
Can be reused

3. Enzymes Are specific for what they will catalyze Are reusable
End in –ase
-Sucrase
-Lactase
-Maltase

4. How do enzymes work?
Enzymes work by weakening bonds of the reactant, which lowers activation energy (energy needed to start the reaction)

5. Enzymes Without Enzyme With Enzyme Free Energy
Progress of the reaction
Reactants
Products
Free energy of activation

6. Substrates The substance (reactant) an enzyme acts on is the substrate
Joins
Substrate

7. Active Site
A restricted region of an enzyme molecule which binds to the substrate.
Active Site
Enzyme
Enzyme + Substrate = ENZYME-SUBSTRATE COMPLEX
Substrate

8. How does a substrate fit with its enzyme?
TWO MODELS:
1.) Lock-and-Key Model
2.) Induced Fit Model

9. Lock-and-Key
Active Sites are SPECIFIC and COMPLEMENTARY for their substrates.
This is like a LOCK & KEY
Idea of “1 substrate for 1 enzyme”

10. Induced Fit A change in the shape of an enzyme’s active site
Induced by the substrate
Idea that 1 enzyme can have more than 1 substrate. Is still specific for its substrates, but may be more than 1

11. Induced Fit
A change in the configuration (shape) of an enzyme’s active site
Induced by the substrate.
Enzyme
Active Site
substrate
induced fit

12. What Affects Enzyme Activity?
Three factors:
1. Environmental Conditions
2. Cofactors and Coenzymes
3. Enzyme Inhibitors

13. Environmental Conditions
1. Extreme temperatures are the most dangerous
- High fevers
2. pH (most like pH near neutral)
3. Ionic concentration (salt ions)
ALL OF THESE FACTORS DISRUPT THE SHAPE OF THE ENZYME, SO IT WILL UNFOLD (DENATURE)

14. Cofactors and Coenzymes
1. Metal ions (zinc, iron) = Cofactors (nonorganic)
2. Vitamins (biotin, B12) = Coenzymes (organic)
Sometimes need for proper enzymatic activity…help to further speed up the reaction
Example: Iron (Cofactor) must be present in the structure of hemoglobin in order for it to pick up oxygen.

15. Enzyme Inhibitors: 1st Type
1. Competitive inhibitors: chemicals that resemble an enzyme’s normal substrate and compete with it for the active site.
Enzyme
Substrate
Competitive inhibitor

16. Enzyme Inhibitors: 2nd Type
2. Noncompetitive inhibitors:
Inhibitors that do not enter the active site, but bind to another part of the enzyme causing the enzyme to change its shape, which in turn alters the active site.
Enzyme
Noncompetitive
Inhibitor
Substrate
active site
altered

17. POINTS TO REMEMBER Most are PROTEINS Act as CATALYSTS
 ACTIVATION ENERGY
SPEED  Reactions
Provide an ACTIVE SITE to bind to its substrate and form an enzyme-substrate complex
Are SPECIFIC for its substrate(s)
Are REUSABLE (after converting a reactant to product, can do this multiple times!)