Enzymes

ENZYME: biological catalyst made of protein which alter the rate of chemical reactions, remaining unchanged at the end of reaction.
SUBSTRATE: substances upon which enzymes act.

WHY BIOLOGICAL?
Produced by living cells
Protein in nature (and hence can be denatured by extreme pH and heat)

WHY CATALYSTS?
Alter rate of chemical reactions
But are not changed at the end of the reaction
Hence required in minute (ie small) amounts as they can be REUSED

Lock & Key Hypothesis
To explain why enzymes are SPECIFIC in action
Enzyme = Lock
Substrate = Key
For key to fit into lock, it has to have a shape that is COMPLEMENTARY to the shape of the lock. Similarly, for the enzyme to act on the substrate, the substrate must have a shape that is COMPLEMENTARY to the ACTIVE SITE of the enzyme.

Why are enzymes important?
Enable all the chemical reactions in the body to run, without requiring extreme conditions like high heat.
Hence body must maintain a suitable environment for enzymes to function as near optimum as possible.

Commonly used terms:
1. Control: Set-up used to provide standard conditions to be compared with experimental conditions, to study the effect of a factor on a process by removing or varying the factor. In enzyme experiments, the control set-up usually shows that the changes observed are due to the action of the enzyme (eg. oxygen gas produced is due to action of catalase). The control usually involves a similar set-up, but uses boiled enzyme that would be denatured, and hence will not be able to produce a reaction.

2. Action of enzyme: Basically used to refer to the effect of the enzyme (eg. Action of catalase- Breaks down hydrogen peroxide into oxygen which appears as froth.)

3. Chemical nature: Refers to what kind of chemical makes up the molecule, and the characteristics of the chemical (eg. protein in nature means the molecules can be denatured by high heat/extreme pH). Read up important concepts for temp and pH effects on enzymes in notes.


4. Rate of reaction: Measure of how fast a reaction is running, based on
a. Amount of substrate used up/Time taken
b. Amount of product formed/Time taken

5. Effects of Substrate and Enzyme Concentration
Terms to take note of:
• Limiting factor: A factor that directly affects the rate at which chemical reaction progresses. Increasing quantity of this factor will increase the rate of reaction.
• End Point: Reaction has been completed. All substrates have been used up.
• Saturation Point: All the enzymes have been made use of. Enzyme concentration is the limiting factor.

*For enzyme graphs;
take note of the axes, gradient of the curves and where the curve plateaus.