GRE Subject Test: Biology : Understanding Antibodies and Antigens

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #1 : Understanding Antibodies And Antigens

Which of the following statements is true concerning antibodies?

Possible Answers:

Antibodies mark pathogens to be destroyed by phagocytic cells

An antibody can attach to multiple pathogens

Antibodies are created by helper T-cells

Antibodies destroy pathogens once attached

Correct answer:

Antibodies mark pathogens to be destroyed by phagocytic cells

Explanation:

An antibody is very specific and will only attach to one antigen. Once it does, the antibody can signal the pathogen or infected cell to be destroyed by macrophages and other phagocytic cells in the body, such as cytotoxic T-cells. The antibodies themselves cannot destroy the pathogen.

T-cells serve important functions in the communication and stimulation of antibody production, but do not actually produce antibodies.

Example Question #2 : Understanding Antibodies And Antigens

Which of the following statements is true about antibodies?

Possible Answers:

They are found on the surface of helper T cells.

They can be secreted by plasma cells.

They have two recognition sites which can recognize two different antigens.

They are seen immediately following an infection.

Correct answer:

They can be secreted by plasma cells.

Explanation:

Antibodies are part of the adaptive immune response, which means that they are formed later in an infection. Because both recognition sites have the same structure, they are responsive to only one type of antigen. They are located on the outside of B cells, and can be released freely into the plasma by plasma cells.

Example Question #3 : Understanding Antibodies And Antigens

Which antibody type is able to cross the placental barrier in order to provide temporary passive immunity for the fetus?

Possible Answers:

IgG

IgE

IgM

IgA

Correct answer:

IgG

Explanation:

Placental crossing is done mainly by IgG antibodies. These fast-acting antibodies provide temporary immunity for the fetus until it is able to have its own immune system produce sufficient antibody amounts.

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