Q.85 Which one of the following organic compounds is composed of only (i) a nitrogen
containing base, (ii) a single five-carbon sugar, and (iii) a triphosphate?
(A) Nucleoside
(B) Nucleotide
(C) Base
(D) Nucleic acid
Answer: (B) Nucleotide
Nucleotides form the basic building blocks of DNA and RNA, precisely matching the description of an organic compound with a nitrogen-containing base, a single five-carbon sugar, and a triphosphate group. This structure distinguishes them in molecular biology, especially for CSIR NET Life Sciences preparation.
Option Analysis
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(A) Nucleoside: Contains only a nitrogen-containing base and a five-carbon sugar (ribose or deoxyribose), lacking the phosphate or triphosphate group.
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(B) Nucleotide: Composed exactly of a nitrogenous base, one pentose sugar, and one to three phosphate groups (including triphosphate forms like ATP).
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(C) Base: Refers solely to the nitrogen-containing molecule (purine or pyrimidine), without sugar or phosphate components.
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(D) Nucleic acid: Polymers of many nucleotides linked via phosphodiester bonds, far exceeding a single sugar or isolated triphosphate.
Nucleotides represent the core organic compounds featuring a nitrogen containing base, single five-carbon sugar, and triphosphate, essential for CSIR NET Life Sciences aspirants tackling molecular biology questions. This precise composition powers genetic information storage in DNA and RNA.
Nucleotide Structure Breakdown
Nucleotides consist of three subunits: a nitrogenous base (adenine, guanine, cytosine, thymine, or uracil), a pentose sugar (ribose in RNA or deoxyribose in DNA), and a phosphate chain often as triphosphate. The triphosphate form, like in ATP, enables energy transfer and polymerization.
Key Differences Table
| Component | Nucleoside | Nucleotide | Base | Nucleic Acid |
|---|---|---|---|---|
| Nitrogen Base | Yes | Yes | Yes | Many |
| Five-Carbon Sugar | Yes (single) | Yes (single) | No | Many |
| Triphosphate | No | Yes | No | Polymer chain |
CSIR NET Exam Relevance
For competitive exams like CSIR NET, distinguishing nucleotide from nucleoside hinges on the phosphate group—nucleosides lack it entirely. Nucleic acids, being polymers, contain thousands of such units linked covalently. Focus on these for biomolecule structure questions.
