1. Enzymes: Biological Catalysts
ENZYMES are group of molecules that are PROTEINS and that speed up the rate of chemical reactions
ALL ENZYMES ARE PROTEINS, BUT NOT ALL PROTEINS ARE ENZYMES
Enzymes are unchanged during the course of a chemical reaction and can thus be reused
Enzymes lower the start up (activation) energy of a chemical reaction

2. Chemical Reaction Review
What are reactants?
What are products?

3. Enzymes and Activation Energy
Add in sucrose, glucose, and fructose to the picture

4. How Enzymes Work Bind to the reactants.
Reactants are called substrates.
The area where enzymes bind is called the active site.
Help the chemical reaction proceed.
Holds the 2 substrates in position so that they can react with each other.
Can twist substrates slightly to break bonds.

5. Enzyme catalysis .

6. Enzymes are specific
1. An enzyme can catalyze only one particular reaction.
2. Enzymes are specific because their shape fits only one substrate.
3. Classic Analogy:
Enzymes and substrates fit
together like locks in keys:
only one substrate with a
certain shape can fit in to
the specific shape of an
enzyme.

7. A New Way Of Thinking
Induced Fit: enzymes have a general shape that changes as the substrate binds

8. Enzymes are important…
in regulating chemical pathways.
for synthesizing materials needed by cells.
in catalyzing chemical reactions that release energy.
in regulating chem. rxns that are important for info. transfer.

9. Temperature affects enzymes
Moving molecules depend on temp.
warmer = faster; colder = slower
Rate of chemical rxns depends on temperature.
Faster molecules = more collisions b/w enzyme and substrate
Too much heat can destroy
enzymes by causing them to
lose their shape
(denaturation).

10. Temperature affects enzymes in animals
Cold-blooded animals
Body temp. is the same as environment.
Enzyme activity level depends on environment.
Warm-blooded animals
Body temp. is constant
Use respiration to produce heat to keep temp. constant.

11. pH affects enzyme function
Many enzymes work best at pH = 7
Enzyme shapes are influenced by the presence/absence of H+
Some enzymes work best at acidic pH!

12. Concentration of substrate influences enzyme activity
How much substrate is available can determine how quickly the enzyme can work.
The more substrate, the more likely an enzyme is to collide with substrate.