Chapter 13, Problem 13A

Summary Introduction

To label:

To label the diagram of the antibody.

Introduction:

The structure of the antibody resembles the alphabet Y and consists of 4 proteins (2 light chains and 2 heavy chains).

Pictorial representation:

Figure: The structure of an antibody molecule.

The correct answers are:

1. Antigen binding sites
2. Light chain
3. Heavy chain

V stands for the variable region

C stands for the constant region

Explanation for the answers:

1. Antigen binding site − These are the sites on the amino-terminal end of both light and heavy chain. It provides a site of attachment for the antigen.
2. Light chain − There is 2 identical light chains consisting of polypeptides. They are bound to the heavy chain via disulfide bonds and non-covalent interactions.
3. Heavy chain − There are 5 types of heavy chains (accordingly antibodies are named) and attached to each other via the disulfide bonds.

V stands for variable region. The amino-terminal end of both heavy and light chain of about 100-110 amino acids vary considerably among antibodies and hence are called as variable region.

C stands for the constant region. The carboxy-terminalend of both light and heavy chain shows similarity among antibodies and hence is considered as constant regions.