Question

In fibrous proteins, polypeptide chains are held together by?
A. Van der waals forces
B. Electrostatic forces of attraction
C. Hydrogen bonds
D. Covalent bonds

Answer 1

Hint: We all know that proteins are highly complex nitrogenous organic compounds of very high molecular masses. All proteins are polymers of alpha amino acids. For example: Glycine, Alanine, Valine etc. On the basis of molecular structure we can classify proteins as fibrous proteins and globular proteins.

Complete step by step answer:
As we know that fibrous proteins are long narrow in shape and they are insoluble in water. The proteins which consist of linear, thread-like polypeptide chains arranged or twisted to form fibers are called fibrous proteins.
Example: Collagen in tendons, myosin in muscles etc.
The characteristics of fibrous proteins are:
1.Linear thread like structure.
2. Long chain is held together by hydrogen bonds and some disulphide bonds.
We must have to know that the fibrous and globular shapes of proteins are found in the tertiary structure of the protein, the tertiary structure of the protein is stabilized by hydrogen, disulphide, and van der Waals forces. Therefore, we can say that when the polypeptide chain runs parallel and is held together by hydrogen and disulphide bonds then the proteins formed are known as fibrous proteins.

Therefore, the option C is correct.

Note: We need to remember that a hydrogen bond (often informally abbreviated H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative atom or group, particularly the second-row elements nitrogen (N), oxygen (O), or fluorine (F)—the hydrogen bond donor (Dn)—and another electronegative atom bearing a lone pair of electrons—the hydrogen bond acceptor (Ac). The hydrogen bond is responsible for many of the anomalous physical and chemical properties of compounds of N, O, and F.