1. Unit II Respiration & Photosynthesis
Enzymes
Unit II Respiration & Photosynthesis

2. Enzymes
ENZYMES
3-D shape
Active site- enzyme interacts with substrate (lock and key)
Lowers EA (activation energy),
Speeds up reaction

3. Enzymes are catalysts
Catalysts= chemical that affects the speed a chemical reaction happens without being used up in the reaction
Enzymes can speed up or slow down how fast a reaction happens
They only work on reactions that would happen anyway In other words, they do not cause the reaction to happen.

4. This energy is called causes the reaction to proceed
Enzymes are proteins that have a very specific function and only work for specific reactions.
Reactions need a certain amount of energy to happen= Activation Energy (EA)
Ex: Boulder on top of the hill
This energy is called causes the reaction to proceed
Enzymes reduce the amount of activation energy needed

5. Progress of the reaction
without
enzyme
EA without
enzyme
EA with
enzyme
Reactants
Energy
Net
change
in energy
(the same)
Reaction with
enzyme
Figure 5.14 The effect of an enzyme is to lower EA.
Products
Progress of the reaction

6. Enzyme Shape
Enzymes have specific shapes, which enable them to attach to certain molecules, which are called “Substrates”.
The point of attachment is called the “active site.”
The active site is usually a groove or pocket which fits with a certain enzyme shaped like a puzzle piece or handshake.
Once the reaction happens, the enzyme detaches from the substrate and is used again for another reaction of the same type.

7. “ASE”= Enzyme suffix
Enzymes are generally named after the molecule it works on by changing the last three letters to “ase”.
Example: Enzyme Sucrase, (breaks bond between glucose and fructose in sucrose)
Sucrose acts on the substrate sucrose breaking it into  Glucose + Fructose
Sucrase Only works on sucrose and no other disaccharide.

8. 3 major things will affect how well an enzyme works:
Temperature
Most enzymes work best in a certain temperature range
Most humans enzymes work best between degrees C (Around human body temperature)
pH (acid or base)
Most human enzymes work best between pH 6 and pH 8
Enzymes in the human stomach work best at acidic levels (ph 1-2) due to presence of stomach acid used in digestion.
Salt content in environment
Excessive salt content can interfere with active site function.