When something occurs or repeats at regular intervals it is called

Collagen is a "fibrous proteins" present in the extracellular matrix.

Explanation:

Protein are made up of hundreds or thousands of smaller units called amino acids and is made of carbon, hydrogen, oxygen, nitrogen and sometimes sulfur and is found in many foods. Proteins are organic molecules found in living organisms.

There are three types of proteins; fibrous, globular, and membrane.

Collagen which is a fibrous proteins, form muscle fiber, tendons, connective tissue and bone.

Collagen are naturally occurring proteins that consist of single molecules made up of amino-acids, which are in turn built of carbon, oxygen and hydrogen. It is mostly found in fibrous tissues such as tendons, ligaments, and skin.

The synthesis of collagen occurs in two stages: intracellular and extracellular.

Collagen is an abundant connective tissues such as cartilage, tendons, bones, and ligaments. Collagen is a contributing factor to variation in meat tenderness and texture.