Image Source Oct 14, 2020 14:35 IST · 3 min read
They are called carbohydrates as they comprise carbon, hydrogen, and oxygen at their chemical level. The main function of carbohydrates is to provide energy and food to the body and to the nervous system.
It is also involved in fat metabolism (chemical processes inside body) and prevents ketosis.
There are many types of carbohydrates. The main carbohydrates found in our food are in the form of starch, fibers and sugars.
We can easily test if a food item contains starch by putting 2-3 drops of dilute iodine solution on it. If the food turns blue-black, it indicates that it contains starch.
The food containing carbohydrates are converted into glucose or blood sugar during the process of digestion by the digestive system. Our body utilizes this sugar as a source of energy for the cells, organs, and tissues. The extra amount of energy or sugar is stored in our muscles and liver for further requirement.
An enzyme by name amylase assists in the breakdown of starch into glucose.
Sources: Sweet potato, Potato, Sugarcane, Papaya, Melon, Mango, Maize, Bajra, Rice, Wheat etc.
Hexose sugars are carbohydrates made of six carbon atoms. Glucose, fructose and galactose are all examples of hexose. Hexose sugars are energy sources for the metabolism.
Deoxyribose and Ribose sugars are fundamental components of DNA and RNA respectively. Both of these are pentose sugars.
| Carbohydrates | Sources |
|---|---|
| Fructose | Fruits |
| Galactos and Lactose | Dairy products |
| Maltose | Cereal, beer, potatoes, processed cheese, pasta |
| Sucrose | Sugar and Honey |
Classification
The carbohydrates are further classified into simple and complex which is mainly based on their chemical structure and degree of polymerization.1) Simple Carbohydrates
Simple carbohydrates have one or two sugar molecules, these molecules are digested and converted quickly resulting in a rise in the blood sugar levels. They are abundantly found in milk products, beer, fruits, refined sugars, candies, etc.These carbohydrates are called as empty calories, as they do not possess fiber, vitamins and minerals.
1.1) Monosaccharides
Monosaccharides are simple sugars in which there are one oxygen atom and two hydrogen atoms for each carbon atom present in the molecule.Monosaccharides cannot be broken down into smaller molecules of other carbohydrates, Glucose, Fructose, Galactose and Mannose are examples of Monosaccharides.
Mannose is not an essential nutrient; it can be produced in the human body from glucose, or converted into glucose.
1.2) Disaccharides
Disaccharides are carbohydrates made up of two monosaccharides and which are missing one molecule of water (dehydration).Table sugar Sucrose is a disaccharide made of one molecule of glucose and one molecule of fructose.
Maltose is also a disaccharide that consists of two glucose molecules.
Lactose or milk sugar is another disaccharide made of one molecule of galactose and one molecule of glucose.
1.3) Oligosaccharides
Carbohydrates formed by the condensation of 2-9 monomers are called oligosaccharides. By this convention, trioses, pentoses, hexoses are all oligosaccharides.2) Complex Carbohydrates
Polysaccharides (Complex Carbohydrates) are polymers of monosaccharides made of more than 10 units. Common examples of polysaccharides are cellulose, starch, glycogen, chitin etc.In complex carbohydrates, molecules are digested and converted slowly compared to simple carbohydrates. They are abundantly found in lentils, beans, peanuts, potatoes, peas, corn, whole-grain bread, cereals, etc.
Starch is a polysaccharide comprising glucose monomers joined in a 1,4 linkages. The simplest form of starch is the linear polymer amylose; amylopectin is the branched form.
Glycogen is called animal starch. It has a structure similar to starch, but has more extensive branching.
Glycogen and starch are called storage polysaccharides, they store energy while Cellulose and Chitin are called structural polysaccharides and provide support for organisms without a bony skeleton.
Chitin exists in the shells of arthropods such as crabs, shrimps, and insects and is also produced by fungi and bacteria.
Cellulose is a structural carbohydrate and is the main structural component of the plant cell wall.