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Glucose pentaacetate does not react with hydroxylamine. This indicates that glucose:

Answer: Exists as a cyclic hemiacetal lacking free CHO.

  • A Contains five hydroxyl groups in a ring
  • B Has a branched carbon skeleton in solution
  • C Exists as a cyclic hemiacetal lacking free CHO
  • D Is a non-reducing disaccharide in the solid state

Correct answer: C. Exists as a cyclic hemiacetal lacking free CHO

Explanation: The pentaacetate has no free aldehyde, so no oxime forms. This shows glucose exists largely in a cyclic hemiacetal form with no free CHO group.

Peptide Bond Formation (Condensation)H₂N-CH(R₁)-C(=O)OHAmino acid 1+HNH-CH(R₂)-COOHAmino acid 2H₂N-CH(R₁)-CO-NH-CH(R₂)-COOHDipeptide+ H₂OThe -OH (from acid 1) and -H (from amine 2) combine to release water, forming the -CO-NH- peptide bond

Two amino acids join via a condensation reaction: the carboxyl -OH of one and an amine -H of the other are eliminated as water, leaving a peptide bond (-CO-NH-) linking them into a dipeptide; repeating this builds a full protein chain.

Concept context

The chemistry of life: carbohydrates, proteins, lipids, nucleic acids, enzymes, and vitamins. Understand their structures, classification, and biological functions. Highly relevant for NEET and Class 12 board exams.

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