Chemistry Multiple Choice Questions on “Drug-Target Interaction”.
1. Drugs that block the binding site of an enzyme form a substrate are called ______
a) inhibitors
b) poisons
c) messengers
d) receptors
Answer: a
Clarification: Drugs that either prevent the enzyme from holding the substrate or prevent it from providing functional groups that attack the substrate, are called enzyme inhibitors. These inhibit the catalytic activity of enzymes.
2. Which of the following drugs will inhibit the activity of the shown enzyme?
a) A
b) B
c) C
d) D
Answer: a
Clarification: The shape of the active site resembles a triangle, which means that the substrate should also have a similar shape. The drug that will inhibit the activity of this enzyme should closely resemble the substrate and block the active site. These are called competitive inhibitors.
3. All drugs block enzyme activity by occupying the active site before the substrate.
a) True
b) False
Answer: b
Clarification: Drugs prevent the attachment of substrate to enzymes by two different ways. One is the competitive approach where it occupies the active site, and the other is non-competitive way in which it does not occupy the active site.
4. A certain compound X occupied a site of an enzyme exactly opposite to that of the active site. This immediately resulted in the change of shape of the active site. X is called a ______
a) competitive inhibitor
b) non-competitive inhibitor
c) competitive messenger
d) receptor
Answer: b
Clarification: Non-competitive inhibitors are drugs that affect the catalytic activity of enzymes by changing the shape of the active site by binding to the enzyme at some other site. This prevents the substrate from binding to the enzyme.
5. A certain compound occupied a site Y of an enzyme near to the active site. This immediately resulted in the change of shape of the active site. Y is called a/an ______
a) inactive site
b) binding site
c) non-competitive site
d) allosteric site
Answer: d
Clarification: When a drug binds to an enzyme from a site other than the active site, it is called an allosteric site. Binding to this site causes the change in shape of active site such that the substrate cannot recognise it.
6. If the bond between the enzyme and inhibiting drug is very strong, which of the following takes place?
a) The active site slowly regains its original shape
b) The enzyme develops a new active site
c) The enzyme is blocked temporarily
d) The body synthesizes a new enzyme
Answer: d
Clarification: When there is a strong covalent bond between the enzyme and the drug, the enzyme is blocked permanently. This results in the degradation of the entire drug-enzyme complex and the synthesis of a new enzyme.
7. Which of the following is incorrect regarding receptors?
a) They have constant shape
b) They are proteins
c) The shape of receptors binding site changes to fit the messenger
d) They are present in the cell membrane
Answer: a
Clarification: Receptors are proteins that are embedded in the cell membrane with the binding site protruding outwards. They change the shape of the binding site to accommodate the incoming messenger and facilitate communication.
8. Which of the following is not a reason for the selectivity of receptors towards messengers?
a) Shape of binding site
b) Structure
c) Amino acid composition
d) Location in the membrane
Answer: d
Clarification: There are lots of different types of receptors in the body at different locations. They interact with different kinds of chemical messengers. Their selectivity for one messenger over the other is because of the difference in their binding sites, structure and composition of amino acids.
9. The drugs that are used when there is a lack of natural chemical messenger is called ______
a) antagonists
b) agonists
c) analgesics
d) narcotics
Answer: b
Clarification: Agonists are drugs that replicate the behaviour and properties of the chemical messenger and activate the receptor. These are used when the actual messenger is not present in the body.
10. Antagonists do not allow the transfer of message through receptors.
a) True
b) False
Answer: a
Clarification: Antagonists bind to the receptor at the binding site and inhibit its natural communicative function. This prevents the message to be passed into the cell.