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: Classify raffinose.
Raffinose is a trisaccharide, so on complete hydrolysis it must release exactly three monosaccharide units.
Step 2: Recall its make-up.
Raffinose can be viewed as a sucrose unit joined to a galactose unit, sucrose itself being glucose plus fructose.
Step 3: List the building blocks.
From that make-up, the three monomers are galactose, glucose and fructose - one of each.
Step 4: Write the hydrolysis.
$\text{Raffinose} + 2\text{H}_2\text{O} \rightarrow \text{Galactose} + \text{Glucose} + \text{Fructose}$, confirming three different sugars.
Step 5: Eliminate the wrong options.
Any option naming two of the same sugar (two galactose, two fructose, or two glucose) is wrong, because raffinose has one each of three distinct sugars.
Step 6: Select the answer.
One glucose, one fructose and one galactose corresponds to option (4).
\[ \boxed{\text{Glucose + Fructose + Galactose (one each), option 4}} \]