Biology Biomolecules UHS 2023
PMDC Verified Question 48 of 142
Most of the monosaccharides form a ring structure when in solution. For example ribose will form a five cornered ring known as ____.
A
Ribofuranose
B
Glucopyranose
C
Glyceraldehyde
D
Acetaldehyde
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Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Ribofuranose
Concept:

In an aqueous solution, pentoses and hexoses undergo intramolecular reactions to form stable, closed rings.

Solution:

  • Ribose is a 5-carbon pentose sugar.


  • When it forms a closed ring in solution, it strictly forms a 5-membered ring (four carbon atoms and one oxygen atom in the ring).


  • Chemically, any 5-membered sugar ring is termed a "furanose" (named after the chemical furan). Thus, cyclic ribose is technically termed Ribofuranose.


Why other options are incorrect:

  • Glucopyranose: A 6-membered ring (pyranose) formed by Glucose, not Ribose.


  • Glyceraldehyde / Acetaldehyde: Small linear molecules that do not form these complex rings.

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