Q. No27. Which one of the following bonds is NOT present in ATP?
The bond NOT present in ATP is α-glycosidic.
ATP (adenosine triphosphate) consists of adenine, ribose sugar, and three phosphate groups linked by specific bonds. Evaluating each option reveals that α-glycosidic bonds do not exist in its structure.
Option Analysis
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(A) Phosphoanhydride: These high-energy bonds connect the β-γ and α-β phosphates, enabling ATP’s role in energy transfer.
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(B) N-glycosidic: This bond links adenine’s N9 to ribose’s C1′, forming the nucleoside adenosine.
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(C) Phosphoester: The α-phosphate attaches to ribose’s C5′ via this bond.
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(D) α-glycosidic: Absent in ATP; α-glycosidic bonds link sugars in polysaccharides like starch, but ATP uses N-glycosidic for base-sugar.
ATP, the cell’s energy currency, features a precise molecular structure critical for exams like CSIR NET Life Sciences. Understanding which bond is NOT present in ATP—among phosphoanhydride, N-glycosidic, phosphoester, and α-glycosidic—helps master nucleotide chemistry.
ATP Structure Essentials
Adenosine triphosphate comprises adenine (purine base), β-D-ribofuranose (ribose sugar), and triphosphate. The N-glycosidic bond joins adenine to ribose C1′. A phosphoester bond connects ribose C5′ to α-phosphate. Phosphoanhydride bonds link α-β and β-γ phosphates, storing ~30.5 kJ/mol energy each.
No α-glycosidic bond appears; these form O-links between sugars (e.g., α-1,4 in glycogen), irrelevant to ATP’s N-linked nucleoside.
Why α-Glycosidic is Absent
α-Glycosidic bonds involve anomeric carbon (C1′) of one sugar bonding via oxygen to another sugar’s hydroxyl. In ATP, ribose C1′ bonds to nitrogen (N-glycosidic), not oxygen, distinguishing nucleosides from disaccharides.
| Bond Type | Location in ATP | Present? | Example in Biology |
|---|---|---|---|
| Phosphoanhydride | α-β, β-γ phosphates | Yes | Energy release on hydrolysis |
| N-Glycosidic | Adenine N9 – Ribose C1′ | Yes | All nucleotides |
| Phosphoester | Ribose C5′ – α-phosphate | Yes | Nucleotide backbone |
| α-Glycosidic | None | No | Starch, glycogen |
Exam Relevance for CSIR NET
This question tests nucleotide vs. carbohydrate bond knowledge. Phosphoanhydride bonds’ high energy drives metabolism; hydrolysis yields ADP + Pi. N-glycosidic and phosphoester ensure stability. Practice distinguishing: ATP lacks sugar-sugar O-bonds like α-glycosidic.
