Match the class of compounds given in Column-I with their functions given in Column-II and select the correct option:

	Column-I		Column-II
(a)	Antagonists	(i)	Communicate message between two neurons and that between neurons to muscles.
(b)	Agonists	(ii)	Bind to the receptor site and inhibit its natural function.
(c)	Chemical messenger	(iii)	Crucial to body’s communication process.
(d)	Inhibitors	(iv)	Mimic the natural messenger.
(e)	Receptors	(v)	Inhibit activities of enzymes.

	a	b	c	d	e
1.	iv	iii	v	ii	i
2.	ii	iii	i	v	iv
3.	ii	iv	i	v	iii
4.	iv	iii	v	ii	i

A.Antagonist- 

drugs are used when blocking of message is required. e.g., dopamine antagonist is a drug which blocks the dopamine receptors by receptor antagonism.
B. Agonist - 

drugs are useful when there is a lack of chemical messenger, e.g., heroin.
C.  chemical messengers 

These are received at the binding sites of the receptor. These communicate a message between two neurons and that between neurons to muscles.
D. Inhibitors -

 block the binding site of the enzyme and prevent the binding of the substrate, or Inhibit the catalytic activity of the enzyme.
E. Receptors - 

are Proteins that are crucial to the body's communication. They are embedded in of the membrane in such a way that their small part possessing active site projects out of the surface of the membrane and opens on the active site projects membrane.