Proteins- Structure and Function

Solomon Cardy

Levels of structure

In multi organism cells are specialized according to the function they perform. Specialized cells are grouped together in tissues.

1. Epithelial tissue.

1.1. Cuboidal Epithelium:

As their name implies, cuboidal cells are roughly square or cubical in shape. Each cell has a spherical nucleus in the centre. Cuboidal epithelium is found in glands and in the lining of the kidney tubules as well as in the ducts of the glands. They also constitute the germinal epithelium which produces the egg cells in the female ovary and the sperm cells in the male testes.

1.2. Ciliated Columnar Epithelium:

These are simple columnar epithelial cells, but in addition, they posses fine hair-like outgrowths, cilia on their free surfaces. These cilia are capable of rapid, rhythmic, wavelike beatings in a certain direction. This movement of the cilia in a certain direction causes the mucus, which is secreted by the goblet cells, to move (flow or stream) in that direction. Ciliated epithelium is usually found in the air passages like the nose. It is also found in the uterus and Fallopian tubes of females. The movement of the cilia propels the ovum to the uterus.

2. Connective tissue.

2.1. Collagen.

Collagen is the main protein of connective tissue. It has great tensile strength, and is the main component of ligaments and tendons. It is responsible for skin elasticity, and its degradation leads to wrinkles that accompany aging. Collagen also fills out the cornea where it is present in crystalline form.

3. Muscle tissue.