1. Fibrous Proteins:
* Structure: Long, thin, and often insoluble in water. They consist of polypeptide chains arranged in parallel, forming fibers or sheets.
* Function: Provide structural support, strength, and flexibility to tissues. Examples include:
* Collagen: Found in skin, bones, tendons, and cartilage, provides tensile strength.
* Keratin: Found in hair, nails, skin, and feathers, provides protection and structural integrity.
* Elastin: Found in ligaments, arteries, and lungs, allows for stretching and recoil.
2. Globular Proteins:
* Structure: Compact, spherical, and usually water-soluble. They have a more complex three-dimensional structure with folded polypeptide chains.
* Function: Involved in a wide range of biological processes, including:
* Enzymes: Catalyze biochemical reactions.
* Hormones: Regulate body functions.
* Antibodies: Defend against pathogens.
* Transport proteins: Carry molecules across cell membranes.
* Storage proteins: Store nutrients like iron (ferritin).
Remember, these are just two broad categories. There are many other protein classes based on specific structures and functions, such as membrane proteins, motor proteins, and regulatory proteins.
