Concept 4 Review

The Structure of Sugar

Sugars, defined by the presence of hydroxyl and carbonyl groups, are the simplest form of carbohydrates.

Each carbon atom in a sugar molecule carries both a hydrogen atom and a hydroxyl group (-OH), except that one carbon atom always contains a carbonyl oxygen (=O), as shown in the figure below.

of glucose, fructose, hexane; Sugar molecule and hydrocarbon

The major differences between sugars and hydrocarbons are:

If the carbonyl group is located at one end of the sugar, it is classified as an aldehyde group, and the sugar is an aldose sugar. If the carbonyl group is located on an internal C atom, it is classified as a keto group, and the sugar is a ketose sugar.

Sugar names end with the suffix -ose. Common examples are glucose (grape sugar), fructose (fruit sugar), sucrose (cane sugar), and lactose (milk sugar).