Chemistry MCQs for NEET — Practice Questions with Answers

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.

The text states secondary structure arises due to 'hydrogen bonding between C=O and –NH– groups.' For tertiary and quaternary structures, it mentions 'hydrogen bonds, disulphide linkages, van der Waals and electrostatic forces of attraction,' indicating disulfide linkages are found at these higher levels, but not explicitly mentioned for secondary structure stabilization.

The text states: 'A number of polyhalogen compounds e.g., dichloromethane, chloroform, iodoform, carbon tetrachloride, freon and DDT have many industrial applications.'

The text mentions: 'Our body produces iodine containing hormone, thyroxine, the deficiency of which causes a disease called goiter.'

The text states: 'However, some of these compounds cannot be easily decomposed and even cause depletion of ozone layer and are proving environmental hazards.'

The text states: 'Synthetic halogen compounds, viz. chloroquine is used for the treatment of malaria; halothane is used as an anaesthetic during surgery.'