1. Catalyst
A substance that speeds up the rate of a
chemical reaction
Enzymes are BIOLOGICAL catalysts
Reaction could
still happen, but
not as fast!
What enzyme
works on

2. Catalyst
Catalysts decrease the amount of energy
needed to start the chemical reaction
(activation energy)
Why need?
•Reaction too slow
•Activation energy
too high
Compare
these

3. Enzymes
Proteins that act as biological catalysts
Enzymes are NOT used up in a reaction
Enzymes are very specific
– Substrates and enzyme fit like “lock and key”
Substrates are the REACTANTS
PRODUCT

4. Enzymes
Enzymes are affected by changes in
pH, temperature, regulatory molecules,
substrate concentration