This set of Class 12 Biology Multiple Choice Questions & Answers (MCQs) focuses on “Human Health and Disease – Humoral Immunity-2” for NEET Preparation.
1. Which region of an antibody is also called a ‘Fragment of Crystallization’?
a) Fc region
b) Fab region
c) CC region
d) NN region
Explanation: Fc region of an antibody is also called as a Fragment of Crystallization. It is responsible for the effector function. It is also called a constant region. It determines the isotype of an immunoglobulin.
2. What is the approximate weight of Heavy and Light chains respectively?
a) 50,000 Da and 25,000 Da
b) 25,000 Da and 50,000 Da
c) 75,000 Da and 25,000 Da
d) 75,000 Da and 50,000 Da
Explanation: Each antibody molecule has four peptide chains, two long chains called heavy or H chain each of molecular weight 50,000 Da and two short chains called light or L chains each of approximate molecular weight 25,000 Da.
3. Which region of an antibody is also called as ‘Variable Region’?
a) Fc region
b) Fab region
c) NN region
d) CC region
Explanation: Fab region of an antibody is also called a variable region. The Fab portion is so called because it is the fragment of the molecule which is antigen binding or a paratope.
4. Antigens are generally Antibody generating molecules.
Explanation: The word ‘Antigen’ has been derived from ‘Antibody Generating’ because they stimulate the production of antibodies in response to an infection.
5. Which of the following antibodies constitute the largest proportion of the total antibodies present?
Explanation: IgG antibodies constitute 75% of the total antibodies present in the blood. It is present in the monomer form and has two paratopes. It also evokes the complementary system and Opsonisation.
6. Which of the following is the smallest antibody?
Explanation: IgG is the smallest of all the antibodies. Also, it is the only antibody that can cross the placenta and confer immunity to the foetus. It only has two paratopes.
7. Which of the following is correctly matched in the following figure?
a) Antigen binding site
b) Disulphide bonds
c) Heavy chain
d) Light chain
Explanation: Antigen binding site is correctly matched in the following figure. The correct labelling of the following figure is:
8. Which of the following antibody is the first line of defence against inhaled and ingested pathogens?
Explanation: IgA antibody is the first line of defence against inhaled and indigested pathogens because it is present in cell secretions like milk, saliva, mucous etc. It is also found in Colostrum.
9. In which of the following places antibody IgA is not present?
c) Digestive tract
d) Respiratory tract
Explanation: IgA antibodies are present in the mucous secretions of the respiratory tract, the upper part of the digestive tract and the vagina. IgG antibody is the only antibody which can cross Placenta.
10. Which of the following is an Allergy Mediated antibody?
Explanation: IgE is an Allergy Mediated antibody because it activates the histamine secreting cells. It is less than 1% of the total antibodies. IgE antibody also appears to play an important role in parasitic infection.
11. Which of the following antibodies are present on the surface of B-lymphocytes?
Explanation: IgD are membrane-bound antibodies present on the surface of B-lymphocytes. They appear to have a role in activating and suppressing the lymphocyte activity found in large quantities in the cell membrane of many B-cells.
12. Antigens can be only of one specific nature.
Explanation: Antigens can be of any chemical nature. Antigens are of two types-Complete and Incomplete antigens. Complete antigens have epitopes or antigen determinant sites. Incomplete antigens lack epitopes but when attached to a large carrier such as a protein, they become capable of producing antibodies.
Sanfoundry Global Education & Learning Series – Biology – Class 12.
To practice all chapters and topics of Biology for NEET Exam, here is complete set of 1000+ Multiple Choice Questions and Answers.
- Get Free Certificate of Merit in Biology - Class 12
- Participate in Biology - Class 12 Certification Contest
- Become a Top Ranker in Biology - Class 12
- Take Biology - Class 12 Tests
- Chapterwise Practice Tests: Chapter 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
- Chapterwise Mock Tests: Chapter 1, 2, 3, 4, 5, 6, 7, 8, 9, 10