Describe the IgG Immunoglobulin.

Immunoglobulin:

1. Immunoglobulin is glycoprotein molecules that are produced by plasma cells.
2. They recognize and bind to specific antigens and help in their destruction.
3. They are also known as antibodies.

Immunoglobulin IgG:

1. IgG class of immunoglobulins is composed of four different subtypes called IgG subclass and are represented as $\mathrm{IgG}1$, $\mathrm{IgG}2$, $\mathrm{IgG}3$ and $\mathrm{IgG}4$.
2. It is made up of four polypeptide chains, two identical heavy and two identical light chains.
3. It has a flexible Y-shaped structure.
4. They have a molecular weight of $150\mathrm{kDa}$, the heavy chain is $50\mathrm{kDa}$ and the light chain is $25\mathrm{kDa}$.
5. The two heavy chains are linked by disulfide bonds and a heavy chain is linked to the light chain by disulfide bonds.
6. IgG is the most abundant antibody found among all the antibodies.
7. IgG is the only immunoglobulin that passes through the human placenta.