1. How do enzymes catalyse the reaction:-

i. The first function of an enzyme is to hold the substrate molecule for a chemical reaction. The active site of enzymes holds the substrate molecule in suitable position so that it can be attacked by reagent effectively

ii. The second function of enzymes is to provide functional groups which will attack the substrate to carry out the chemical reaction. The amino acid present on active site of enzyme provides free amino group to attack the substrate and bring the chemical reaction.

2. Drug enzyme interation:-
i. Drugs which inhibit any of the two activities of the enzyme are called the inhibitors they block the binding site thus preventing the binding of the substrate to active site.
ii. Drugs which compete with the natural substrate for their attachment on the active sites of enzymes are called competitive Inhibitors.
iii. Some drugs do not binds to the active sites but binds to a different site of the enzyme called allosteric site
iv. In the bond formed between an enzyme and the drug (inhibitor) is a strong covalent bond. Then enzyme is blocked permanently.

v. Drug and substrate competing for active site.


They are the proteins which are crucial to the communication system in the body. They present in cell membranes small parts of their possess the active site out of surface of the cell membrane.

Chemical messenger:-
In the animal body, the message between two neurons and muscles in communicated through certain chemical substances called the chemical messengers. To accommodate these chemical messenger the shape of receptor protein changes and messenger give the message to cell without entering into it.

Type of chemical messengers:-

a. Hormones:-
They are a group of biomolecules which are produced the ductless (endocrine) glands they enters the blood stream and travel in the body to activate all receptors to attend their message.

b. Neurotransmitters:-
Nerve transfer message through neurotransmitters. They are small molecules such as acetylcholine, dopamine and serotonin.

c. Why drug causes side effect:-

Side effect of drugs is caused when a drug binds to more than one site of receptor. Example some anti depressant drugs binds to serotonin receptor.

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