Question

The incorrect statement from the following with respect to carbohydrates is:

• A. All monosaccharides are reducing sugars.
• B. The monosaccharide units obtained from hydrolysis of oligosaccharides are always the same.
• C. Starch and cellulose are typical examples of polysaccharides, which are very high molecular weight compounds of more than ten monosaccharide units.
• D. Open chain and cyclic structures co-exist at equilibrium that are responsible for certain properties as in the case of D-(+)-glucose.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Carbohydrates are classified based on the number of sugar units they produce upon hydrolysis.
Step 2: Detailed Explanation:
(a): All monosaccharides (e.g., glucose, fructose) reduce Tollen’s and Fehling’s reagents. (Correct)
(b): Oligosaccharides (2–10 units) can yield different sugars. For example, sucrose (an oligosaccharide/disaccharide) yields glucose and fructose. They are not always the same. (Incorrect)
(c): Polysaccharides consist of a large number of monosaccharide units. (Correct)
(d): Glucose exists as an equilibrium mixture of open-chain and cyclic forms. (Correct)
Step 3: Final Answer:
Statement (B) is incorrect.