Question 1

Why is an antibody represented as H₂L₂?

Accepted Answer

Each antibody molecule contains four peptide chains: two longer heavy (H) chains and two smaller light (L) chains. Therefore NCERT represents an antibody as H₂L₂.

Question 2

Where are the antigen-binding sites on an antibody?

Accepted Answer

An antibody has two antigen-binding sites, one at each tip of its Y-shaped molecule. The variable regions of a heavy chain and a light chain meet at each tip to form a matching binding pocket.

Question 3

Which cells produce antibodies?

Accepted Answer

B-lymphocytes produce antibodies in response to pathogens. T-cells do not themselves secrete antibodies, but they help B cells to produce them.

Question 4

What is the difference between humoral and cell-mediated immunity?

Accepted Answer

Humoral immunity is antibody-mediated; NCERT links the name to antibodies found in the blood. Cell-mediated immunity is mediated by T-lymphocytes and is important in responses such as graft rejection.

Question 5

Why is the secondary immune response stronger than the primary response?

Accepted Answer

Acquired immunity is characterised by memory. The first encounter produces a low-intensity primary response, while a later encounter with the same pathogen elicits a highly intensified secondary or anamnestic response.

Antibody Structure — Heavy and Light Chains in 3D

About this lab

Practice