Q.9 Find the wrong one out –
I. Nucleotide minus phosphoryl group is nucleoside
2. Purines and pyrimidines are double and single ring compounds. respectively.
3. Purines and pyrimidines are linked to sugars by a peptidoglycan bond.
4. Adenosine and Uridine are ribonucleosides.
Statement 3 is incorrect because purines and pyrimidines link to sugars via a glycosidic bond, not a peptidoglycan bond (which relates to bacterial cell walls).
Option Analysis
Statement 1: Nucleotide to Nucleoside
A nucleotide consists of a nitrogenous base, pentose sugar, and phosphate group(s). Removing the phosphoryl (phosphate) group yields a nucleoside (base + sugar only). Correct.
Statement 2: Purine and Pyrimidine Rings
Purines (adenine, guanine) have double rings (purine ring: pyrimidine fused with imidazole). Pyrimidines (cytosine, thymine, uracil) have single rings. This holds for both DNA and RNA. Correct.
Statement 3: Bond Between Bases and Sugars
Nitrogenous bases attach to the C1′ of ribose/deoxyribose via N-glycosidic bonds (β-N-glycosidic linkage). Peptidoglycan bonds do not exist here; peptidoglycan is a bacterial polymer with peptide cross-links. Incorrect—this is the wrong one out.
Statement 4: Ribonucleosides
Adenosine (adenine + ribose) and uridine (uracil + ribose) are indeed ribonucleosides, used in RNA. (Deoxy versions are deoxyadenosine, deoxyuridine for DNA). Correct.
The wrong one out nucleotide nucleoside purines pyrimidines MCQ tests nucleic acid basics crucial for NEET, GATE Life Sciences exams. It covers nucleoside formation, base structures, bonding, and examples like adenosine uridine, helping spot errors in biomolecule concepts.
Nucleotide vs Nucleoside Basics
Nucleotides lose phosphate to form nucleosides; both build DNA/RNA.
Purine Pyrimidine Structures
Purines: double-ring; pyrimidines: single-ring for base pairing.
Key Bonding Error
Glycosidic links bases to sugar—not peptidoglycan, a cell wall term.
| Statement | Fact | Status |
|---|---|---|
| 1. Nucleotide minus phosphoryl | Forms nucleoside | Correct |
| 2. Purines double, pyrimidines single | Ring structures | Correct |
| 3. Peptidoglycan bond to sugar | Actually glycosidic | Wrong |
| 4. Adenosine/Uridine ribonucleosides | RNA components | Correct |
Focus on glycosidic bonds for exam success in molecular biology.
