NEET Practice Questions (MCQs) with Answers & Solutions

Metamerism is a type of isomerism where compounds have the same molecular formula but different alkyl groups on either side of a functional group. $C_2H_5 - S - C_2H_5$ (diethyl sulfide) can show metamerism because changing the alkyl groups on either side of the sulfur atom can result in different compounds like $CH_3 - S - C_3H_7$. The other options do not show metamerism because changing the alkyl groups on either side of the functional group does not result in different compounds.

When a chiral center is produced in a reaction, it typically results in the formation of a racemic mixture, which is an equimolar mixture of the two enantiomers (dextrorotatory and laevorotatory forms). This is because the reaction does not preferentially produce one enantiomer over the other, leading to a mixture that is optically inactive as the rotations cancel each other out.

The given information suggests that the hydrocarbon molecule 'A' is a planar cyclic structure where all the carbon-carbon bonds are of equal length between 1.34 Å (which is typical for double bonds) and 1.54 Å (which is typical for single bonds). This implies that the bonds are likely to be somewhere in between, hinting at possible resonance structures. A common example fitting this description is benzene, which is a planar cyclic molecule with bond angles of $120^ ext{°}$ due to its $sp^2$ hybridized carbon atoms.

Proteins, enzymes, and lipids are all types of biomolecules. Proteins are composed of amino acids and perform a variety of functions in the body such as catalyzing metabolic reactions and DNA replication. Enzymes are a specific type of protein that act as catalysts in biochemical reactions. Lipids are a diverse group of compounds, including fats, oils, and hormones, that are insoluble in water but soluble in organic solvents. Thus, the correct answer is 'all of the above'.

Formic acid is an organic compound and the simplest carboxylic acid, but it is not typically classified as a biomolecule. Biomolecules are organic molecules that are involved in the maintenance and metabolic processes of living organisms. Examples include nucleic acids (DNA and RNA), vitamins, and carbohydrates. Therefore, formic acid is not considered a biomolecule.

Dextrin is a carbohydrate that is not soluble in water and is tasteless. Other carbohydrates like lactose, fructose, and melitriose are soluble in water and have a taste.