Carbohydrates -  Definition, Type, Examples

Carbohydrates are organic compounds containing carbon, hydrogen and oxygen which constitute sugars (starch, cellulose, glucose etc) and supply calories for body activity. One gram of carbohydrate provides 4.2 calories of energy. The ratio of hydrogen to oxygen in the Carbohydrate is 2:1. The sources of carbohydrates are rice, wheat, honey, sugar, potato, carrot, banana, bread etc. Deficiency of carbohydrates causes weight loss and weakness. Based on the number of sugar units they can be classified into, Monosaccharides, Disaccharides, Oligosaccharides and Polysaccharides. Starch, Sugar, Cellulose, Glucose, Inulin, Glycogen and Chitin are various types of Carbohydrates.

Types of Carbohydrates

1. Starch

Glucose is a basic sugar that plants use to make starch. The most significant dietary supply for higher animals is a polysaccharide reserve found in plants. Grains and tubers contain starch in the form of starch. Iodine Test is the test related to finding the presence of starch. When starch reacts with iodine solution, it produces a deep blue color.

2. Sugars

Since sugars are in their most basic form, they are also known as simple carbohydrates. Sugars are classified into monosaccharides, disaccharides and polysaccharides.

i. Monosaccharides - Also called as simple sugars. Examples of monosaccharides include glucose, fructose, and galactose. 

ii. Disaccharides - Also called as double sugars. Examples of disaccharides include Sucrose (Table Sugar), Lactose and Maltose.

iii. Polysaccharides - Also called as complex carbohydrates, which are chains of glucose molecules. Examples of polysaccharides include starch and glycogen.

3. Cellulose

The most abundant organic material in plants is cellulose, which is found only in plants. It is the main component of the cell wall of plants. Cellulose is totally absent in animal cell. Cellulose, though not digested has great importance in human nutrition. It is major constituent of fibre.

4. Glucose

Glucose is a type of sugar also called as grape sugar. Glucose is a product of photosynthesis in green plants and is the chief source of energy for most living organisms. The presence of glucose in any subsance can be identified using benedict test. If sugar is present in the Benedict test, the result is a brick red color.

5. Inulin

Inulin not a sugar itself, and is often used as a sugar substitute due to its prebiotic properties and potential health benefits. 

6. Glycogen

Glycogon is the carbohydrate reserve in animal hence it is often reffered to as animal starch. It is present in high concentration in liver, followed by muscle, brain etc. Glycogen is also found in plants that do not possess chlorophyll.

7. Chitin

Chitin is a structural polysaccharide found in exoskeleton of some invertebrates. eg: insects and crustaceans.