3. Which of the following molecules have a sugar moiety as an integral part?
a. Amino acids
b. Nucleic acids
c. Phospholipids
d. All of the above
Nucleic acids contain sugar as an essential structural component, making option b the correct answer in this CSIR NET Life Sciences MCQ on biomolecules. Standard amino acids and phospholipids lack covalently bound sugar in their core structures.
Option Analysis
a. Amino acids
Amino acids consist of a central alpha carbon linked to an amino group, carboxyl group, hydrogen, and variable R-group side chain. No sugar moiety appears in any of the 20 standard proteinogenic amino acids; exceptions like amino sugars (glucosamine) represent modified carbohydrates, not core amino acids.
b. Nucleic acids
Nucleic acids (DNA, RNA) form polymers of nucleotides, each comprising a nitrogenous base, pentose sugar (deoxyribose in DNA, ribose in RNA), and phosphate. The sugar provides the backbone via phosphodiester bonds, making it integral to structure and function.
c. Phospholipids
Phospholipids feature a glycerol backbone esterified to two fatty acids and a phosphate head group, often linked to choline or ethanolamine. Sugar remains absent from this core amphipathic structure essential for membranes.
d. All of the above
Incorrect, as only nucleic acids qualify; amino acids and phospholipids exclude sugar moieties.
Biomolecule Structures Table
| Biomolecule | Core Components | Sugar Present? | Example Role |
|---|---|---|---|
| Amino acids | α-C, NH₂, COOH, R-group | No | Protein synthesis |
| Nucleic acids | Base + sugar + phosphate (nucleotide) | Yes (pentose) | Genetic information |
| Phospholipids | Glycerol + 2 fatty acids + phosphate | No | Membrane fluidity |
This MCQ tests Unit 1 knowledge of biomolecule composition, emphasizing nucleotide structure over lipid or protein basics. For CSIR NET success, memorize that sugars define carbohydrates and nucleic acids distinctly.
