Sample 1Medium
A diagram shows a Y-shaped antibody molecule: two longer polypeptide chains form the stem and continue into the arms, and two shorter chains lie along the outer side of the arms, with antigen-binding sites at the tips of the arms. How is this molecule represented, and which cells produce it?
- A
H4, produced by T-lymphocytes
- B
H2L2, produced by T-lymphocytes
- C
H2L2, produced by B-lymphocytes
- D
H1L3, produced by macrophages
Show the answer
The answer is C.Each antibody has four peptide chains, two small light chains and two longer heavy chains, so it is written H2L2. B-lymphocytes produce antibodies in response to pathogens.
- A.
The molecule has two heavy and two light chains, and T-cells do not secrete antibodies.
- B.
Antibodies are produced by B-lymphocytes; T-cells mediate cell-mediated immunity.
- D.
There are two heavy and two light chains, and macrophages do not make antibodies.
NCERT: Class 12 Biology, Chapter 7, 7.2
Sample 2NEET level
Consider the following statements about acquired immunity: 1. B-lymphocytes produce antibodies into the blood in response to pathogens. 2. T-lymphocytes do not secrete antibodies themselves but help B-cells produce them. 3. Each antibody molecule has four peptide chains: two small light chains and two longer heavy chains. 4. The colostrum secreted in the first days of lactation is rich in IgG antibodies that protect the infant. Which of the statements above are correct?
- A
1 and 2 only
- B
1, 2 and 3 only
- C
2, 3 and 4 only
- D
1, 3 and 4 only
Show the answer
The answer is B.B-lymphocytes produce antibodies, while T-lymphocytes do not secrete antibodies but help B-cells produce them; each antibody is H2L2, with two light and two heavy chains. Colostrum is rich in IgA antibodies, not IgG, so statement 4 is false.
- A.
Leaves out statement 3, which correctly describes the H2L2 structure of an antibody.
- C.
Includes statement 4, which is false (colostrum carries IgA), and leaves out the correct statement 1.
- D.
Includes statement 4, which is false, and leaves out the correct statement 2.
NCERT: Class 12 Biology, Chapter 7 (Human Health and Disease), Immunity