What Process Splits Polysaccharide Into Monosaccharides?

There are two types of chemical reactions that occur in human beings:
Anabolism; and
Catabolism.

Any reaction in which a group of molecules combines together to form a bigger unit is known as anabolism. Any reaction in which a larger unit is broken down into smaller units is known as catabolism.
So, when polysaccharides are broken down into monosaccharides, it is known as catabolism and when the monosaccharides combine to form a polysaccharide it is anabolism. The mechanism of anabolism here is polymerization.
Starch, obtained from foods such as potatoes and rice, is a polysaccharide and is broken down into a monosaccharide glucose by catabolism. This glucose is used to make energy for our body.
If there is an excess of glucose in the body, it is converted into another polysaccharide, glycogen which can be stored in the liver and muscles. It is built up by anabolism.