CHAPTER AT A GLANCE
1. Drugs are chemical compounds of low molecular masses ( 100 – 500 u). These interact with
molecular targets and produce a biological response. When the biological response is therapeutic and
useful, these chemicals are called medicines. Use of chemicals for therapeutic effect is called
Chemotherapy.
2. Drugs are classified into four classes as follows:
(i) On the basis of pharmacological effect.
(ii) On the basis of drug action.
(iii) On the basis of chemical structure.
(iv) On the basis of molecular targets.
3. Enzymes are the proteins which act as biological catalysts in the body.
4. Receptors are the proteins which are crucial to the communication system in the body.
5. In their catalytic activity, enzymes perform two functions:
(i) To hold the substance for a chemical reaction
(ii) To provide functional groups that will attack the substrate and carry out chemical reaction.
6. The drugs which can block the binding site of the enzyme and prevent the binding of substrate or can
inhibit the activity of enzyme are called enzyme inhibitors.
7. Drugs which compete with the natural substrate for their attachment on the active sites of enzymes are
called competitive inhibitors.
8. Drugs which bind to a site of enzyme other than active site called allosteric site, change the shape of the
active site in such a way that the substrate cannot recognise it, are called non-competitive inhibitors.
9. If the bond formed between an enzyme and an inhibitor is a strong covalent bond and cannot be broken
easily, then the enzyme is blocked permanently and the body then degrades the enzyme-inhibitor
complex and synthesizes the new enzyme.
10. Receptor proteins are embedded in the cell membrane in such a way that their small part possessing
active site projects out of the surface of the membrane and opens on the outside region of the cell
membrane.
11. In the body, message between two neurons and that between neurons to muscles is communicated
through chemicals called chemical messengers which are received at the binding sited of the receptor
proteins.
12. To accommodate a messenger, shape of the receptor site changes and this brings about the transfer of
message into the cell.
13. Receptors show selectivity for one chemical messenger over the outer because their binding sites have
different shape, structure and amino acid composition.
14. Antagonists are the drugs that bind to the receptor site and inhibit its natural function. These are useful
when blocking of a message is required.
15. Drugs that mimic the natural messenger by switching on the receptor are called agonists. These are
useful when there is a lack of natural messenger.
16. Analgesics are the drugs which relieve or decrease pain.
1. Drugs are chemical compounds of low molecular masses ( 100 – 500 u). These interact with
molecular targets and produce a biological response. When the biological response is therapeutic and
useful, these chemicals are called medicines. Use of chemicals for therapeutic effect is called
Chemotherapy.
2. Drugs are classified into four classes as follows:
(i) On the basis of pharmacological effect.
(ii) On the basis of drug action.
(iii) On the basis of chemical structure.
(iv) On the basis of molecular targets.
3. Enzymes are the proteins which act as biological catalysts in the body.
4. Receptors are the proteins which are crucial to the communication system in the body.
5. In their catalytic activity, enzymes perform two functions:
(i) To hold the substance for a chemical reaction
(ii) To provide functional groups that will attack the substrate and carry out chemical reaction.
6. The drugs which can block the binding site of the enzyme and prevent the binding of substrate or can
inhibit the activity of enzyme are called enzyme inhibitors.
7. Drugs which compete with the natural substrate for their attachment on the active sites of enzymes are
called competitive inhibitors.
8. Drugs which bind to a site of enzyme other than active site called allosteric site, change the shape of the
active site in such a way that the substrate cannot recognise it, are called non-competitive inhibitors.
9. If the bond formed between an enzyme and an inhibitor is a strong covalent bond and cannot be broken
easily, then the enzyme is blocked permanently and the body then degrades the enzyme-inhibitor
complex and synthesizes the new enzyme.
10. Receptor proteins are embedded in the cell membrane in such a way that their small part possessing
active site projects out of the surface of the membrane and opens on the outside region of the cell
membrane.
11. In the body, message between two neurons and that between neurons to muscles is communicated
through chemicals called chemical messengers which are received at the binding sited of the receptor
proteins.
12. To accommodate a messenger, shape of the receptor site changes and this brings about the transfer of
message into the cell.
13. Receptors show selectivity for one chemical messenger over the outer because their binding sites have
different shape, structure and amino acid composition.
14. Antagonists are the drugs that bind to the receptor site and inhibit its natural function. These are useful
when blocking of a message is required.
15. Drugs that mimic the natural messenger by switching on the receptor are called agonists. These are
useful when there is a lack of natural messenger.
16. Analgesics are the drugs which relieve or decrease pain.
