1. 2-4 Enzymes

2. Question:
What are enzymes?

3. Enzymes
Answer: 1. Proteins: most enzymes are proteins. 2. Catalyst: chemical agent that accelerates a reaction without being permanently changed in the process.

4. Enzymes
3. Selective: enzymes are specific for which they will catalyze (speed up) 4. Recycled: enzymes are reusable. 5. “ase” endings: examples: sucrase maltase lactase

5. Question:
How do enzymes work?

6. Enzymes
Answer:
Enzymes speed up the cell’s chemical reactions by lowering the free energy of activation.

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

8. Substrate
The substance (reactant) an enzyme acts on.
Enzyme
Substrate

9. Active Site
A restricted region of an enzyme molecule which binds to the substrate.
Enzyme
Substrate
Active Site

10. Induced Fit
A change in the configuration of an enzyme’s active site (H and ionic bonds are involved).
Induced by the substrate.
Enzyme
Active Site
substrate
induced fit

11. Enzymatic Reaction substrate (Peroxide) + enzyme (Catalase in potato)
enzyme-substrate complex 
and +
catalase
Water Oxygen
products enzyme

13. What Affects Enzyme Activity?
Two factors:
1. Environmental Conditions
2. Concentration of enzyme and substrate

14. 1. Environmental Conditions
Enzymatic reactions are very specific. The following environmental conditions affect enzymatic reactions:
1. Temperature (extremes most dangerous):
- high temps may denature the enzyme.
2. pH (most like pH - neutral)

15. Concentrations A. the concentration of enzyme
Increasing enzyme concentration will increase the enzyme reaction rate.
B. the concentration of substrate
A higher concentration of substrate does not increase the reaction rate.

16. Mini Activity #1 Time (seconds) Number of broken Toothpicks 10 30 60
120

17. Mini Activity #1
One person’s fingers are the enzyme TOOTHPICKASE (one person is the timer, and one is the recorder)
The toothpicks are the SUBSTRATE
Toothpickase is a DIGESTIVE ENZYME. It breaks down toothpicks into two units.
To break the toothpick, place a toothpick between the thumb and the first finger of each hand. Break the toothpick in two pieces.
ALWAYS place broken toothpicks back in the container, and no peeking when breaking toothpicks!

18. Mini Activity #1 1. What was the enzyme? 2. What was the substrate?
3. What did you notice happening to the substrate as time passed?
4. Did the enzyme ever change? Why?

19. Mini Activity #2
What were to happen if we increased the concentration of rubber bands while the number of toothpicks stayed the same?

20. Mini Activity #2 Time (seconds) Number of Toothpicks Broken 20 40 6080

21. Mini Activity #2
1. Why does toothpickase only bind to toothpicks and not rubber bands?
2. What happens when the concentration of rubber bands is higher than the concentration of toothpicks?
3. What would occur to the reaction rate if there were a higher concentration of toothpickase enzymes?