What are biomolecules /carbohydrates? Classification of carbohydrates explanined in simple manner!

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A living system grows, sustain and reproduces itself. The most amazing things about a living system is that it is composed of non-living atoms and molecules. The pursuit of knowledge of what goes on chemically within a living system falls in the domain of biochemistry. Living systems are made up of various complex bio-molecules like carbohydrates, proteins, nucleic acids, lipids, etc. Proteins and essential constituents of our food. These bio-molecules interact with each other and constitute the molecular logic of life vitamins and mineral salts also play an important role in the functions of organisms. 

Carbohydrates:

Carbohydrates are primarily produced by plats and form a very large group of naturally occurring organic compounds. Some common examples are cane sugar, glucose, starch, etc. Most of them have a general formula, CX(H2O)y, and were considered as hydrates of carbon from where the name carbohydrates was derived. For e.g.the C6(H2O)6. But all the compounds which fit into this formula may not be classified as carbohydrates. Acetic acid (CH3COOH) Fits into this general formula, C2(H2O)2 but is not a carbohydrate. Similarly, rhamnose, C6H12O5 is a carbohydrates but dose not fit in this definition. A large no. of their reaction have shown that they contain specific functional groups. Chemically, the carbohydrates may be defined as optically active polyhydroxy aldehydes or ketones the compounds which produce such units on hydrolysis. Some of the carbohydrates, which are sweet in taste, are also called sugars. The most common sugar, used in our homes is named as sucrose whereas the sugar present in milk is known as lactose. Carbohydrates are also called saccharides (Greek: sakcharon means sugar)

Classification of Carbohydrates:

Carbohydrates are classified on the basis of their behaviour on hydrolysis. They have been broadly divided into following three groups.

1. Monosaccharides: A carbohydrate that can not be hydrolysed further to give simpler unit of polyhydroxy aldehyde or ketone is called a monosaccharide. About 20 monosaccharide are known to occur in nature. Some common examples are glucose, fructose, ribose, etc.

2. Oligosaccharides: Carbohydrates that yields two to ten monosaccharide units, on hydrolysis, are called oligosaccharides. They are further classified as disaccharides, trisaccharides, tetrasaccharides etc,depending upon the number of monosaccharides, they provide on hydrolysis. Amongst these the most common  are disaccharides. The two monosaccharides units obtained on hydrolysis of a disaccharides may be same or different. for e.g. sucrose on hydrolysis gives one molecule each of glucose and fructose whereas maltose gives two molecules of glucose only.

3. Polysaccharide: Carbohydrates which yield a large number of monosaccharide units on hydrolysis are called polysaccharides. Some common examples are starch, cellulose, glycogen, gums, etc. Polysaccharides are not sweet in taste, hence they are also called non-sugars.  
 
The carbohydrates may be also be classified as either reducing or non reducing sugars. All those carbohydrates which reduce Fehlings solution and Tollens' reagent are referred to as reducing sugars.

In disaccharides, if the reducing group of monosaccharides i.e. aldehydic or ketonic groups are bonded, these are non-reducing sugars e.g. sucrose. On the other hand, sugars in which these functional groups are free, are called reducing sugars, for e.g., maltose and lactose.

Monosaccharides:

Monosaccharides are further classified on the basis of number of carbon atoms and the functional group present in them. If a monosaccharide contains aldehyde group, it is known as aldose and if it contains a keto group, it is known as a ketose. Number of carbon atoms constituting the monosaccharide is also introduced in the name as is evident.
1. Glucose 
Glucose occurs freely in nature as well as in the combined form. It is present in a sweet fruits and honey. Ripe grape also contain glucose in large amounts. It is prepared as follows. 
 Preparation of glucose:
1.From sucrose (Cane sugar):
If sucrose is boiled with dilute HCl or H2SO4 in alcoholic solution, glucose and fructose are obtained in equal amounts.


2. From starch:
Commercially glucose is obtained by hydrolysis of starch by boiling it with dilute H2SO4 at 323 K under pressure.




 


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