Collagen is a
A) Phosphoproteins are conjugated proteins, post-translationally modified by the attachment of the phosphate group. Common examples of naturally occurring phosphoproteins are milk protein casein and vitellin of egg yolk
B) The globulins are a family of globular proteins and are insoluble in pure water but dissolve in dilute salt solutions. Some globulins are produced in the liver, while others are made by the immune system. Globulins, albumins, and fibrinogen are the major blood proteins.
C)Derived proteins are proteins derived by partial to complete hydrolysis from the simple or conjugated proteins by the action of acids, alkalies or enzymes. They include two types of derivatives, primary-derived proteins, and secondary-derived proteins.
D)Scleroproteins is of several fibrous proteins of cells and tissues once thought to be insoluble but now known to be dissolved by dilute solutions of acids such as citric and acetic.
The two most important classes of scleroproteins are the collagens and the keratins.
As the collagen belongs to the class of scleroproteins.
Hence, the answer is option D