Question

Which of the following biomolecules is insoluble in water
a. $\alpha $- keratin
b. Haemoglobin
c. Ribonuclease
d. Adenine

Answer 1

Hint: In order to solve this question we must know that proteins are of two types that are globular and fibrous proteins and one of the major differentiating factors is its solubility in water. The fibrous proteins are insoluble in water.

Complete Step by Step Solution:
$\alpha $keratin- Vertebrates have a form of keratin called alpha-keratin, also known as $\alpha $-keratin. The epidermal layer of the skin, mammalian claws, nails, and hairs are all mostly made of this protein. A fibrous structural protein, -keratin is composed of amino acids that repeat to produce the secondary structure. It is hydrophobic in nature i.e. it is insoluble in water.

Haemoglobin- Almost all vertebrates have haemoglobin (Hb or Hgb), a protein that contains iron and is found in erythrocytes or red blood cells (RBC). There are two $\alpha $ subunits and two $\beta $ subunits in each haemoglobin molecule. Each subunit encircles the core heme group, which contains iron and interacts with one molecule of oxygen. It’s soluble in water.

Ribonuclease: A wide class of hydrolytic enzymes known as ribonucleases (RNases) breaks down ribonucleic acid (RNA) molecules. These enzymes accelerate the disintegration of RNA into smaller pieces. They are a superfamily of enzymes that function at the transcriptional and translational levels to catalyse the degradation of RNA.

Adenine: Adenine belongs to a wider group called Purines. Purines contain adenine and guanine which are present in DNA. Purine is a hydrolytic group and is soluble in water.
So the correct option is A. $\alpha $ - keratin

Note: Remember the different categories of biomolecules with their solubility in water. Proteins are of two types that are globular and fibrous. Fibrous proteins are insoluble in water.