Question

1. What is the difference between sucrose, lactose, and maltose? What monosaccharides are involved?

2. If starch and cellulose are both glucose polymers, why can we digest starch but not cellulose?

3. What is a normal fasting blood glucose range for healthy adults?

Answer 1

Answer)1. Sucrose, lactose and maltose are disaccharides , which means they are composed of two monosaccharides.

The basic difference between these three sugars is on the basis of their structures :-

1. Sucrose is alpha 1-2 linkage of glucose molecule with fructose.
2. Lactose is beta 1-4 linkage of glucose and galactose.
3. Maltose is alpha 1-4 linkage of two glucose molecules.

The monosaccharides involved are :-

Maltose is made up of two glucose molecules.

Lactose is made up of one glucose and one galactose

Sucrose is made up of one glucose and one fructose molecule.

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Answer)2. We can digest starch but not cellulose, it is because of the difference in the structure of these two. In starch glucose residues are linked by alpha 1-4 glycosidic bond but in cellulose they are linked by beta 1-4 glycosidic bond.

Also, human produce enzymes (amylase ) , which is capable of breaking bond of starch (alpha 1-4 glycosidic bond) , but not of cellulose (beta 1-4 glycosidic linkage). So, we can digest starch but not cellulose.