Question

Which of the following statements) is/are correct?

(i) Antigen is usually a foreign body that causes the formation of antibodies.

(ii) Antibody is a protein molecule.

(iii) Antigen can be either a protein or polysaccharide molecule.

(iv) Antibody joins an antigen to destroy the latter.

A. (i) and (ii)
B. (i) and (iii)
C. All are incorrect
D. All are correct

Answer 1

Hint:  A substance that stimulates the immune system to produce antibodies is referred to as an antigen. An antibody (Ab), also called immunoglobulin (Ig), is a huge, Y-shaped protein used by the immune system B cells or B lymphocytes to detect and counteract foreign objects.

Complete step-by-step answer:
Antibodies are proteins generated by the immune system in reaction to the infection. They are an essential part of the body's defence system while they work to destroy disease-causing organisms (like bacteria and viruses) and block them from contaminating human cells.
After exposure to foreign particles, which is known as an antigen, antibodies still circulate in the blood, providing protection against prospective exposures to that antigen. Antigens contain chemicals, toxins, viruses, bacteria, or other materials that come from outside the body.
Body cells and tissues, such as cancer cells, also have antigens on them that can trigger an immune response. These antigens may also be used as markers in laboratory tests to detect those cells or tissues. The antigen can be either a polysaccharide molecule or a protein. Antibody joins an antigen to destroy the latter.

Therefore the correct answer is Option D.
Note: Antibodies are proteins that protect humans when an unwanted material enters their body. These are produced by the immune system; antibodies bind to those unwanted substances to remove them from the human system. Immunogens or antigens are materials or toxins in the blood that cause the body to combat them. Two categories of antigens are autoantigens and heteroantigens.