Key Difference: Glucose and Fructose are monosaccharides, whereas Lactose, Maltose and Sucrose are disaccharides. Glucose is classified as an aldehyde, whereas fructose as a ketone. Two glucose units are combined to form Maltose. Sucrose is formed by combination of Fructose and Glucose. Lactose consists of Galactose and Glucose.

Carbohydrates play a vital role as they provide energy to cells in the body. Dietary carbohydrates can be broadly classified into various categories based on the number of sugar units present in them. Monosaccharide consists of one sugar unit, whereas Disaccharide consists of two sugar units. Glucose and Fructose fall in the category of monosaccharide, whereas Sucrose, Lactose and Maltose are types of Disaccharide. Monosaccharides are known as building blocks from which all other big carbohydrates are made.

Glucose and Fructose are common sugars and possess the same molecular formula : C6H12O6. They contain six atoms of carbon and therefore are also known to be a hexose. Glucose is the ‘blood sugar’. It is also known as –glucose, dextrose or grape sugar. Glucose and Fructose possess the same molecular formula. However, they differ in the arrangements of atoms in their structure and therefore are also termed as structural isomers of each other. Fructose is found in fruit, honey, etc.

Glucose is an aldehyde which means that it a compound which contains a carbonyl group with at least one hydrogen attached to it. On the other hand, fructose is a ketone, which means that it is a compound which contains a carbonyl group with two hydrocarbon groups attached to it. 

Lactose is made from the combination of galactose and glucose units. It is the major carbohydrate which is found in milk. D-glucose and D-galactose are joined in a ß-1,4-glycosidic linkage in Lactose. The chemical formula of lactose is C12H22O11. It is a readily digestible source of glucose which is capable of providing energy for the neonate. In case the body is not able to digest significant amounts of lactose, the condition is termed as lactose intolerance.

Maltose or Malt sugar is made from combination of two units of glucose which are joined by α bond. It is not commonly found in food items. However, it can be formed from the digestion of starch. The chemical formula of Maltose is C12H22O11 . It can be found in germinating grain, in small proportion in corn syrup, etc.

Sucrose (table sugar, saccharose) is made from the combination of glucose and fructose units. It generally includes the alpha form of D-glucose and the beta form of D-fructose. The formula of table sugar is C12H22O11. It is a type of sugar which is commonly found in plants.

Glucose and Fructose are monosaccharides, whereas Lactose, Maltose and Sucrose are disaccharides. Glucose is classified as an aldehyde, whereas fructose as a ketone. Two glucose units are combined to form Maltose. Sucrose is formed by combination of Fructose and glucose. Lactose consists of Galactose and Glucose.

Comparison between Glucose, Fructose, Lactose, Maltose and Sucrose:

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