Monosaccharides: Structures & Its Types

“Carbohydrates are mainly found in plant food. It is also found in dairy products in the form of milk sugar called lactose sugar. Carbohydrates-rich foods are bread, pasta, beans, potatoes, rice and cereals. Carbohydrates are a type of macronutrient that is found in food, There are some other macronutrients which are also required for our body to stay healthy.” Carbohydrates are polyhydroxy ketone or aldehyde groups. It is a compound that can be hydrolyzed to them as a carbon hydrate. The general formula of carbohydrate is Cn (H2O)n same as H2O. It depends upon the number of products formed during hydrolysis it has been classified into Monosaccharides, Disaccharides, Oligosaccharides and Polysaccharides. 

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What Is Monosachharide

Monosaccharides are simple sugar. It can not hydrolyse further. It is polyhydroxy aldehyde or ketone unit. Monosaccharides have a sweet taste in nature. It is crystalline and soluble in water. The general formula of monosaccharides is CnH2nOn. It is further classified on the basis of the number of carbon atom presents and the presence of the aldehyde or ketone group.

On the basis of the number of carbon atoms:

Monosaccharides are classified according to the number of carbon atoms are:

Trioses (3C) C3H6O3: Glyceraldehyde and Dihydroxyacetone.

Tetroses (4C)C4H8O4: Erythrose

Pentoses (5C)C5H10O5: Ribose, Ribulose, Xylulose and arabinose.

Hexoses (6C)C6H12O6: Glucose, Fructose, Mannose, Galactose.

Monosaccharides are classified on the presence of aldehyde or ketone group:

Aldoses: Monosaccharide with an aldehyde group.

Ketoses: Monosachharide with a ketone group.

Structure Of Monosaccharide:

There are many arrangements of chemical formulas of monosaccharides, these are called constitutional isomers. All monosaccharides have a backbone carbon chain and that chain is associated with oxygen with either a single bond or double bond. On the monosaccharide there is only one carbon that is bonded with oxygen to double bond, the rest carbons are attached to oxygen with a single bond. The double bond either be aldehyde group on terminal carbon or it may be ketone on central carbon.

Some Examples Of Monosaccharides:

Glucose: 

It is found naturally and ubiquitous. It joins to form disaccharides like maltose (two glucose molecules) and lactose (glucose and galactose). It is one of the products of photosynthesis which occurs in the plant. It provides both energy and structure to many organisms. Glucose breaks down in glycolysis, it provides energy and precursor of cellular respiration. Glucose can be connected with a long string of monosaccharides and forms polysaccharides. The plant produces this as produce cellulose.

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Fructose:

Fructose is a slightly identical molecule to glucose. The formula of glucose and fructose ((CH2O)6) is the same but the structure is different. Fructose is regarded as a naturally-occurring monosaccharide. Natural sources of fructose are sugar cane, honey and fruits. Fructose is a ketonic group monosaccharide and it has a reducing sugar at carbon 2. Fructose is bonded to glucose and forms fructose.

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Galactose:

Galactose is similar to glucose in terms of chemical structure, but the orientation of H and OH are exchanged. Galactose does not occur in a free state. It is composed of a complex biomolecule e.g galactose constitutes glucose forms lactose. It is produced in many organisms, especially in mammals. Galactose helps to form Lactose (Disaccharide) by attached to glucose.

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References: www.biologyonline.com

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