Concept explainers
Introduction:
Adaptive immunity is also called the acquired immune system. It is a selective immunity in which B or T lymphocytes are involved. The two subdivisions of an adaptive immunity are cell-mediated immunity and humoral immunity.
Answer to Problem 1MC
Correct answer:
The plasma cells of B cells synthesize antibodies that provide immunity against the infection. Each antigen has its specific antibodies and each antibody binds to a specific antigen. Therefore, option (b) is correct.
Option (b) is given as “produces antibodies with sites that can bind one or a few antigens”.
Explanation of Solution
Justify reason for the correct statement:
In humoral immunity, antibodies are involved. The B cell antibody recognizes the pathogen that travels in the bloodstream and lymph resulting in their destruction. During the first exposure of antigen, the lymphocytes (B lymphocytes or T lymphocytes) undergo division which results in the formation of plasma cell and memory cells.
The antibodies are secreted by B cells into the bloodstream which is presented on the surface of B cells to which antigen binds. The end of each arm of a heavy and light chain of an antibody consists of variable region which provides a site for antigen binding that binds to a specific antigen.
Hence, option (b) is correct.
Justify reasons for the incorrect statements:
Option (a) is given as “produces antibodies with sites that can bind many different antigens”.
B cell produces antibodies but each antibody is responsible for the binding of specific antigens. It cannot bind to different kinds of antigens as each antigen has its specific antibodies. Hence, it is a wrong answer.
Option (c) is given as “is capable of responding to many unrelated pathogens”.
Each antibody is specific to a particular antigen. It cannot respond to different pathogens as each antibody is antigen specific. Hence, it is a wrong answer.
Option (d) is given as “kills body cells infected with viruses”
Virus-infected cells are not killed by antibodies. Both natural killer cells and cytotoxic T cells recognize infected and cancerous cells by their different surface protein patterns. They recognize these cells as foreign or non-self cells of the body and kill them. Hence, it is a wrong answer.
Hence, options (a), (c), and (d) are incorrect.
B cells produce antibodies into the bloodstream. The amino acid sequence of variable regions of antibody is different in all antibody molecules. Due to this, each antigen has its specific antibodies.
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Chapter 37 Solutions
Biology
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