1. Enzymes How do catalysts speed up chemical reactions?
How do enzymes function as catalysts?

2. Catalysts
Activation energy is energy needed to start a chemical reaction
Sometimes…activation energy required is greater than the energy present so a catalyst is required
Catalysts:
lower the activation energy a reaction needs and
increase the rate of reactions
Examples of catalysts: heat, stirring, crushing

4. Enzymes Function as Catalysts
Enzymes are catalysts for organisms
They lower the activation energy and increase the rate of reactions
Enzymes are proteins
Their function depends on their shape
Lock/Key analogy
Enzyme binds to substrate
Reaction occurs
Enzyme and Product separate

5. Enzymes Function as Catalysts
Enzymes are:
Specific - they only bind with certain substrates
Substrates bind to enzymes by attaching to their active sites
The enzyme then bends around the substrate (induced fit)

7. What affects enzyme action
Correct protein structure
correct order of amino acids
why? enzyme has to be right shape
Temperature
pH (acids & bases)

8. Order of amino acids DNA DNA
Wrong order = wrong shape = can’t do its job!
folded protein
chain of amino acids
DNA
right shape!
folded protein
chain of amino acids
DNA
wrong shape!

9. Temperature Effect on rates of enzyme activity
Optimum temperature
greatest number of collisions between enzyme & substrate
human enzymes
35°- 40°C (body temp = 37°C)
Raise temperature (boiling)
denature protein = unfold = lose shape
Lower temperature T°
molecules move slower
fewer collisions between enzyme & substrate

10. Temperature 37° human enzymes reaction rate temperature
What’s happening here?!
37°
reaction rate
temperature

11. pH Effect on rates of enzyme activity
changes in pH changes protein shape~ Denatures
most human enzymes = pH 6-8
depends on where in body
pepsin (stomach) = pH 3
trypsin (small intestines) = pH 8

12. pH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 stomach pepsin intestines trypsin
What’s happening here?!
reaction rate 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH

13. For enzymes… What matters?
SHAPE!