NEET Practice Questions (MCQs) with Answers & Solutions

The context explains: 'The tertiary structure of proteins represents overall folding of the polypeptide chains i.e., further folding of the secondary structure. It gives rise to two major molecular shapes viz. fibrous and globular.' and 'Tertiary structure is absolutely necessary for the many biological activities of proteins.'

The context details: 'The main forces which stabilize the 2° and 3° structures of proteins are hydrogen bonds, disulphide linkages, van der Waals and electrostatic forces of attraction.'

The context provides: 'Globular proteins... Insulin and albumins are the common examples of globular proteins.'

The context states: 'Some proteins are an assembly of more than one polypeptide or subunits. The manner in which these individual folded polypeptides or subunits are arranged with respect to each other... is the architecture of a protein otherwise called the quaternary structure of a protein. Adult human haemoglobin consists of 4 subunits.'

The context explains: 'When a protein in its native form, is subjected to physical change like change in temperature or chemical change like change in pH, the hydrogen bonds are disturbed. Due to this, globules unfold and helix get uncoiled and protein loses its biological activity. This is called denaturation of Proteins.'

The context implies all levels. It states: 'An enzyme like any protein has a primary structure, i.e., amino acid sequence of the protein. An enzyme like any protein has the secondary and the tertiary structure.' And since some enzymes are multi-subunit, they would also have quaternary structure, similar to other proteins described (e.g., hemoglobin).

The chemistry context states: 'The tertiary structure of proteins represents overall folding of the polypeptide chains i.e., further folding of the secondary structure. It gives rise to two major molecular shapes viz. fibrous and globular.'

The context defines secondary structure as 'regular folding of the backbone... two different types of structures viz. $\alpha$-helix and $\beta$-pleated sheet structure' and tertiary structure as 'overall folding of the polypeptide chains i.e., further folding of the secondary structure. It gives rise to two major molecular shapes viz. fibrous and globular.'

The context states: 'Adult human haemoglobin consists of 4 subunits. Two of these are identical to each other. Hence, two subunits of $\alpha$ type and two subunits of $\beta$ type together constitute the human haemoglobin (Hb).'

The context implies that all higher-order structures (secondary, tertiary, and quaternary) are built upon the primary structure. The tertiary structure is stated to be 'absolutely necessary for the many biological activities,' and the quaternary structure is also involved in the function of multi-subunit proteins like hemoglobin. Therefore, for a protein to function in its 'native form,' all its structural levels are essential.