Question

Which of these is a trisaccharide?
(a)Galactose
(b)Maltose
(c)Raffinose
(d)Mannose

Answer 1

Trisaccharides are sugars that have three monosaccharide subunits. They are also called oligosaccharides. The concerned trisaccharide is a non-reducing sugar as it does not have a free ketone or aldehyde group.

Complete answer:
Oligosaccharides are sugars with 2 to 10 monosaccharide units. When there are three monosaccharide subunits it is known as a trisaccharide. Raffinose is a trisaccharide with three different monosaccharides, one molecule of glucose, one molecule of galactose, and a molecule of fructose.
Rich sources of raffinose include beans, cabbage, broccoli, asparagus are some important sources of raffinose.

Additional Information:
-Depending upon the number of units, sugars can be monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
-Monosaccharides are the basic units that form all other types of sugars.
-The raffinose family of oligosaccharides are derivatives of sucrose, and the most common are the trisaccharide raffinose, stachyose a tetrasaccharide, and pentasaccharide called verbascose.
-They are almost ubiquitous saccharide groups in the plant kingdom, as they are found in a large variety of seeds from many different families, and they are second only to sucrose in abundance as soluble carbohydrates.
So, the correct answer is, “Raffinose.”

Note:
-Glucose which is the most common source of energy in the living world is a monosaccharide.
-Raffinose is not digestible in humans as we lack the enzyme necessary for the breakdown of raffinose.
-However certain bacteria in the large intestines do possess the enzyme and hence the fermentation and breakdown of raffinose may occur there, but in the stomach and the small intestine no digestion of raffinose occurs.