Biology Biomolecules NUMS 2024
PMDC Verified Question 10 of 142
Less reactivity of sucrose is due to its:
A
High solubility in water
B
Polar nature
C
Unavailability of functional group
D
1-2 glycosidic linkage
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Unavailability of functional group
Concept:

Chemical reactivity in sugars is dictated by the availability of a free, unbonded anomeric carbon (the reducing end).

Solution:

  • To be a reactive "reducing sugar" (capable of reacting with Benedict's or Tollens' reagent), a sugar must have a free aldehyde or ketone group that can open up from the ring structure.


  • In Sucrose, the highly reactive anomeric carbon of glucose (C1) is covalently bonded directly to the highly reactive anomeric carbon of fructose (C2).


  • Because both functional groups are entirely locked up in this unique \(\alpha-1,2\) bond, the molecule has absolutely no free functional ends.


  • This complete unavailability of functional groups makes sucrose non-reducing, highly stable, and exceptionally unreactive (perfect for safe transport in plant sap).


Why other options are incorrect:

  • 1-2 glycosidic linkage: While this is the cause of the unavailability, the direct chemical reason for the lack of reactivity itself is the literal "unavailability of the functional group". Both C and D are technically related, but C describes the fundamental chemical mechanism.


  • High solubility / Polar nature: Physical properties unrelated to chemical redox reactivity.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

Previous Question All Biomolecules MCQs Next Question

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.

Enter Arena Sprint iOS App Android App