Monosaccharides (glucose)

Monosaccharides (glucose)

What are Monosaccharides ?

Monosaccharides are the most basic form of carbohydrates. Most organisms produce and store energy by breaking down the monosaccharides glucose and harvest the energy released. This type of glucose are classified in terms of the number of carbon atoms and also the functional group attached to it. The monosaccharide which contains aldehyde is known as aldose and those which contain a ketone group is known as a ketose.

Where can we Find Glucose?

Glucose occurs in both combined as well as in the free state in nature. We can find this in sweet fruits and in honey. Glucose present in ripe grapes in a large amount.

Structure Of Monosaccharides

All the monosaccharides have the formula as (CH2O) n. Here, the two hydrogen atoms and one oxygen atom associate itself to the central carbon molecule. A hydroxyl group is formed when oxygen will bond with hydrogen. Several carbon molecules bond together becuase 4 bonds can form on carbon. One of the carbon will form a double bond with an oxygen in the chain, which is termed as carbonyl group. Depending upon its position, if it is fromed at the end of the chain, then, the monosaccharides is said to belong to the aldose family and if it formed in the middle of the chain, then it belongs to the ketose family.

Preparation of Glucose:

  1. i) From sucrose (cane sugar): We get glucose and fructose in exactly equal amounts if sucrose is boiled with dilute HCl and H2SO4 in an alcoholic solution.

C12H22O11+ H2O → C6H12O6 + C6H12O6

Sucrose Glucose Fructose

  1. ii) From Starch: When hydrolysis of starch is carried out in boiled and diluted H2SO4 at 393 K under pressure, we get glucose.

(C6H10O5)n  + nH2O + H+ → nC6H12O6

Starch or cellulose Glucose

Examples of Monosaccharides

  • Glucose

Glucose molecules can be broken down by glycosis in the process of cellular respiration. Glucose can be connected in long strings of monosaccharides to form polysaccharides. In plants, this thing is produced as cellulose. In plants, each cell is surrounded by cellulose that helps plants stand tall and turgid.

  • Fructose

Fructose belongs to the ketose group. Differently shaped monosacchrides break down specific enzyme. If fructose, combines with other monosaccharides then they form oligosaccharides. Sucrose has a fructose molecule joined with a glucose molecule with the help of a glycosidic bond.

  • Galactose

Galactose is produced by mammals in the form of milk. Lactose holds a lot of energy in its bonds and for breaking down the bonds apart, specific enzymes are developed by offsprings of mammals.

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Practise This Question

Furanose ring structure of fructose is due to hemiacetal formation between