This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Molecular Basis of Immunity”.
1. IgG is the predominant antibody in the secretion of respiratory tract.
Explanation: There are five types of immunoglobulins synthesized by the B lymphocytes. IgA is the predominant antibody found in the secretions of respiratory, digestive and urogenital tract.
2. In all the immunoglobulins, there are _____ type(s) of light chains and ______ type(s) of heavy chain.
a) 2, 1
b) 2, 2
c) 1, 2
d) 1, 1
Explanation: An antibody or immunoglobulin unit consists of four protein chains. Two identical Heavy chains and Light chains joined using a disulphide bridge.
3. Patients suffering from which of the following disease contain large quantities of a single type of antibodies?
b) prostate cancer
c) breast cancer
d) multiple myeloma
Explanation: In multiple myeloma, the plasma cells go out of control and convert into malignant cells. The plasma cells make an abnormal antibody in this disease, the antibodies are known by several names – monoclonal immunoglobulin, monoclonal protein etc.
4. Plasma cells are mainly found in the bone marrow.
Explanation: B lymphocytes play vital role in acquired immunity against diseases and antigens. Upon contact with an antigen, the B cells convert to plasma cells, the latter are found mainly in the bone marrow which is the soft tissue inside the bones.
5. The antigenic determinant is called _________________
Explanation: The antigenic determinant – epitome is the combining site of an antibody that has a complementary stereochemical structure to a particular portion of the antigen. Different antibodies contain variable epitopes.
6. Binding of which of the following antibody’s heavy chain initiates the lysis of bound bacterial cells?
Explanation: Binding of heavy chain of IgM leads to the activation of complement system that initiates the lysis of bacterial cells to which the antibody is bound. Similarly, binding of heavy chain of IgE initiates the allergic responses.
7. In which year was the two “gene – one polypeptide” hypothesis put forward?
Explanation: The “two gene – one polypeptide” hypothesis was put forward in the year 1965 by William Dreyer of the California Institute of Technology and J. Claude Bennett of the University of Alabama.
8. Which segment of chromosome 2 encodes for the V region of antibody?
a) A segment
b) C segment
Explanation: The small portion of the chromosome 2 that encodes for V region (variable region of the immunoglobulin) is called the J segment. On the chromosomes, the genes encoding for variable and constant regions of the chromosomes are segregated.
9. Class-switching of antibodies can occur by changing the ___________________
a) heavy chain
b) light chain
Explanation: The class-switching of antibodies can take place by changing the heavy chains of immunoglobulins without make any change to the antigen binding region. B cells can change the antibodies they make even after producing them.
10. Cyclosporin A is a drug that __________________
a) suppresses the immune system
b) increases body temperature
c) increases the production of antibodies
d) decreases body temperature
Explanation: Cyclosporin A is a drug that suppresses immune system following transplant surgery. It is a cyclic peptide produced by a soil fungus that inhibits the phosphatasein the signaling pathway that leads to the production of cytokines.
11. Fragments of antigens are held at the surface of antigen presenting cells by _________________
c) major histocompatibility complex
Explanation: Fragments of antigens are held at the surfaces of antigen presenting cells (APCs) with the help of MHC (major histocompatibility complex) molecules. The T lymphocytes are activated with the help of antigen presenting cells.
Sanfoundry Global Education & Learning Series – Cell Biology.
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