Two single sugar units can join together to form a disaccharide.
these two sugar units joing together via a condensation reaction.
during a condensation reaction a water molecule is released as the 2 sugar molecules combine.
The bond that forms between 2 glucose molecules is a glycosidic bond or link.
the bond in maltose is known as a 1,4 glycosidic bond because it forms between carbon 1 on one molecule and carbon 4 on the other.
common disaccharides found in food are sucrose, maltose and lactose.
sucrose is formed from glucose and fructose.
it is the usual form in which sugar is transported around a plant.
Maltose is formed from two glucose molecules.
it is the disaccharide produced when amylase breaks down starch.
it is found in germinating seeds such as barley as they break down their starch stores for food.
Lactose is formed from galactose and glucose.
it is the sugar found in milk.
more disaccharide info.
The glycosidic link between 2 sugar units in a disaccharide can be split by hydrolysis.
This is the reverse of condensation. water is added to the bond and the molecule splits in two.
Hydrolysis of carbohydrates takes place when carbohydrates are digested in the gut, and when carbohydrate stores in a cell are broken down to release sugars.
if monosaccharides are eaten they are rapidly absorbed into the blood causing a sharp rise in blood sugar.
Polysaccharides and disaccharides have to be digested into monosaccharides before being absorbed.
this takes some time, so it does not cause swings in blood sugar levels like monosaccharides.
some people are intolerant to Lactose in milk.
one solution is to hydrolyse the lactose in milk, which converts the disaccharide lactose into the monosaccharide glucose and galactose.