Question

The units of monosaccharides present in raffinose are

• A. Two Galactose and one Fructose
• B. Two Fructose and one Glucose
• C. Two Glucose and one Fructose
• D. Glucose, Fructose and Galactose (one unit of each)

Hint:

Think of raffinose as an extension of standard table sugar: $\text{Sucrose} = \text{Glucose} + \text{Fructose}$. If you attach a single Galactose ring onto that pair, you get the trisaccharide Raffinose!

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks for the fundamental monomeric monosaccharide building units that make up the chemical structure of the oligosaccharide known as raffinose.

Step 2: Key Formula or Approach:
Raffinose is a classic trisaccharide found in many vegetables and grains. Hydrolysis of a trisaccharide breaks its glycosidic linkages to yield exactly three component monosaccharide sugar molecules.

Step 3: Detailed Explanation:
Raffinose has a molecular formula of $\text{C}_{18}\text{H}_{32}\text{O}_{16}$. When it undergoes complete chemical or enzymatic hydrolysis, the breakdown resolves into three distinct monomer units:
$$\text{Raffinose} + 2\text{H}_2\text{O} \rightarrow \text{D-Galactose} + \text{D-Glucose} + \text{D-Fructose}$$ Structurally, it can be viewed as a sucrose molecule linked to a galactose unit via an $\alpha(1\rightarrow6)$ glycosidic bond. Hence, it contains precisely one unit of glucose, one unit of fructose, and one unit of galactose, making option (D) the correct choice.

Step 4: Final Answer:
The monosaccharide units present in raffinose are Glucose, Fructose, and Galactose (one unit of each), corresponding to option (D).