Proteins may be classified according to their three-dimensional shapes. Determine whether the following examples and descriptions refer to fibrous proteins, globular proteins, or both fibrous and globular proteins.

-often function as enzymes or transport proteins

-peptide chains arranged in long strands, or fibers

-peptide chains highly folded into spherical shapes

-keratins

-hemoglobin

-water-soluble

-collagens

-insoluble in water

-generally function in structure and support

-often function as enzymes or transport proteins ⇒ globular proteins

-peptide chains arranged in long strands, or fibers ⇒ fibrous proteins

-peptide chains highly folded into spherical shapes ⇒ globular proteins

-keratins ⇒ fibrous proteins

-hemoglobin ⇒ globular proteins

-water-soluble ⇒ globular proteins

-collagens ⇒ fibrous proteins

-insoluble in water ⇒ fibrous proteins

-generally function in structure and support ⇒ fibrous proteins

Explanation:

Fibrous proteins are composed by large polypeptide chains which interact each other and form large structures. They have water insoluble and have structural and protection functions - they are components of cells and tissues. Examples are: collagen, fibronectin, keratin, elastin, actin.

Globular proteins have a spherical compact structure in which hydrophobic aminoacids are buried inside the structure and hydrophilic aminoacids (which can interact with water molecules) are exposed to the exterior medium. For this, they are water soluble. They have often transport and catalytic functions. For example: hemoglobin, mioglobin, albumin, enzymes in general.