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Carbohydrates are compounds containing carbon, hydrogen, and oxygen. They are naturally occurring and have a general formula of C_x(H₂O)_y.

Monosaccharides are the simplest forms of sugar that cannot be broken down further upon hydrolysis.

They can have three to seven carbons in their chains and can also have carbonyl functionality present in their structure other than hydroxyl groups.

• Monosaccharides containing ketone groups (C2 position) are known as ketose. Example: D-fructose
• Monosaccharides containing aldehyde groups (C1 position) are known as aldose. Example: D-glucose.

(a)

A ketotetrose consists of a keto group and contains 4 carbon centers. The structure is shown below:

Ketotetrose

(b)

An aldopentose consists of 5 carbon centers with an aldehyde group. The structure is shown below:

Aldopentose

(c)

Aldotetrose consists of an aldehyde with 3 carbon groups. The structure is given below