Nucleotide Structure and Composition — NEET Biology

Correct answer: B — S2, S4 and S5 are correct

Let's evaluate each statement based on the NCERT text: S1: "Each protein is a polymer of amino acids. As there are 20 types of amino acids (e.g., alanine, cysteine, proline, tryptophan, lysine, etc.), a protein is a heteropolymer and not a homopolymer." This statement is incorrect. S2: "Collagen is the most abundant protein in animal world and Ribulose bisphosphate Carboxylase-Oxygenase (RuBisCO) is the most abundant protein in the whole of the biosphere." This statement is correct. S3: "For example, cellulose is a polymeric polysaccharide consisting of only one type of monosaccharide i.e., glucose. Cellulose is a homopolymer. Starch is a variant of this but present as a store house of energy in plant tissues." This statement is incorrect as starch is also a homopolymer of glucose, not a heteropolymer. S4: "In a polysaccharide chain (say glycogen), the right end is called the reducing end and the left end is called the non-reducing end." This statement is correct. S5: "For nucleic acids, the building block is a nucleotide. A nucleotide has three chemically distinct components. One is a heterocyclic compound, the second is a monosaccharide and the third a phosphoric acid or phosphate." This statement is correct. S6: "Lipids are indeed small molecular weight compounds... Lipids are not strictly macromolecules." This statement is incorrect because lipids are not strictly macromolecules based on their molecular weight, although they are found in the acid-insoluble fraction due to their aggregation into vesicles. Therefore, statements S2, S4, and S5 are correct. The final answer is B. Recap: This question assesses the understanding of key characteristics of various biomacromolecules like proteins, polysaccharides, and nucleic acids, including their polymeric nature, building blocks, and exceptions like lipids.