Question

What are tetrasaccharides? Give their general formula and a few examples.

Answer 1

Let us analyse the name of the given substance:
- Tetra – Four
- Saccharides – Carbohydrates
This breakdown is a big hint and should point you in the right direction towards solving this question.

Complete step by step answer:
Let us first analyse what tetrasaccharides really are before moving on to their general formula.
- A tetrasaccharide is defined as a carbohydrate which, upon hydrolysis, results in the formation of four molecules of similar or different monosaccharides. For instance, stachyose upon hydrolysis gives one molecule each of glucose and fructose and two molecules of galactose. However they are in their respective furanose and pyranose form when involved in tetrasaccharide. Its structure is as follows:

Observe the presence of four different monosaccharide structures present in its overall chemical structure. In its hydrolysis, notice that a water molecule has effectively been added across the glycosidic linkages resulting in the formation of four monosaccharides; glucose, fructose and two molecules of galactose.
$\text{Tetrasaccharide}\xrightarrow{{{H}_{3}}{{O}^{+}}}4\cdot \text{Monosaccharide}$

The general formula of a tetrasaccharide is ${{C}_{24}}{{H}_{42}}{{O}_{21}}$ .
Another very important example of a tetrasaccharide is Maltotetraose, which is a kind of Maltodextrin which is a polysaccharide (many carbohydrates joined together in a molecular chain) that is used as a food additive which is easily digestible, being absorbed as rapidly as glucose and may be either moderately sweet or almost flavourless.
- In addition to them, Lychnose, Maltotetrose and Sesame are also examples of tetrasaccharides.

Note: We can say that all tetrasaccharides are oligosaccharides, but we cannot say that all oligosaccharides are tetrasaccharides because oligosaccharides involves carbohydrates that have three to ten monomer units.