Question

Globular proteins are present in :
(A) blood
(B) keratin
(C) muscles
(D) none of these

Answer 1

Globular means globe-like or spherical shaped proteins. Human body has many types of proteins such as globular, disordered , membrane and fibrous proteins. Most of the proteins are insoluble but globular proteins solubilize to form colloids in water.

Complete step by step answer:
We know that globular proteins are found in blood i.e. in Hemoglobin and also in muscles i.e. in troponin Hemoglobin
Hemoglobin is made up of two word i.e. ‘Haem’ means iron and ‘globin’ is protein. It is present in blood and acts as transporter of oxygen and carbon dioxide in them.
The proteins of Hemoglobin are folded to form a compact, sphere called shape . This protein makes red blood cells dry content by weight. One hemoglobin molecule can carry up to four oxygen molecules in one go.
Thus, blood which contains haemoglobin contains globular proteins.
Troponin
Troponin is a protein of globular shape. It is attached to tropomyosin that lies on actin filaments present in muscles. Troponin blocks the attachment site for myosin on actin to prevent its contraction. There are three types of troponins in the troponin complex that are troponin C, troponin I and troponin T. they are necessary for muscle contraction in skeletal muscles.
There are many other globular proteins present in the human body, examples are :- Insulin, Histone, Immunoglobulin, myoglobin etc. Thus, muscles which contain troponin contain globular proteins.
keratin is a class of tough, fibrous proteins that are the main structural component of hair, nails, horns, feathers, and hooves. Keratins are rich in sulfur-containing amino acids, especially cysteine, thus it lacks globular proteins.

So, the correct answer is Option A.

Note: Globular proteins are also called sphere proteins. They are soluble in water, acids and bases. These proteins are held together tightly by Hydrogen bonds. They are made up of primary, secondary, tertiary or even Quarter nary structures. The troponin is present only in skeletal muscles, not in cardiac or smooth muscles .