What are Carbohydrates?

Carbohydrates include simple sugars and complex polymers. At the molecular level, carbohydrates are organic compounds made of carbon, hydrogen, and oxygen.

Many carbohydrates follow an approximate empirical formula with one oxygen atom and two hydrogen atoms for every carbon atom. For example, glucose has six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.

A single sugar unit is called a monosaccharide. Monosaccharides can be classified based on the number of carbon atoms present. For example, glucose contains six carbon atoms and is classified as a hexose, while ribose contains five carbon atoms and is classified as a pentose.

Monosaccharides are also categorized by the position of the carbonyl group. In aldoses, such as galactose, the carbonyl group is located at the terminal carbon, forming an aldehyde group. In ketoses, such as fructose, the carbonyl group is located on an internal carbon, forming a ketone group.

In aqueous solutions, many monosaccharides exist mainly in ring forms due to intramolecular interactions between the carbonyl group and a hydroxyl group.

Through dehydration synthesis, two monosaccharides can combine to form a disaccharide. For example, glucose and fructose combine to form sucrose, which is a common dietary sugar.

Similarly, repeated linkage of monosaccharide units forms polysaccharides. Among polysaccharides, amylose serves as an energy storage molecule in plants, while cellulose provides structural support in plant cell walls.