Formative Practice 11.1 (Form 4 Biology Textbook Exercise and Answer)

Question 1:
What is the meaning of immunity?

Immunity is the body’s ability to fight against disease infections caused by pathogens or foreign substances, by specifically fighting the particular pathogen.

Question 2:
Name two characteristics of the skin that allows the skin to react as an effective first line of defence.

The skin is a physical defence that prevents the entry of pathogens. The pH of the skin which ranges from 3 to 5 provides an acidic environment which is unfit for microbial growth.

Question 3:
How does the phagocyte destroy pathogens that have penetrated the first line of defence?

Phagocytes carry out phagocytosis by surrounding, trapping and digesting pathogens.

Question 4:
Differentiate between antigens and antibodies.

Antigen is a foreign substance that enters the body.
Antigen is usually a protein molecule found on the wall or external membrane of a pathogen.
Antibody is a protein produced by lymphocytes that functions to destroy the antigen.

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