Carbohydrates play a vital role in a living being. Its importance can be studied under the following headings:
1. Storage role: Carbohydrates serve as the storage of metabolic fuel for a living organism. For example, starch and glycogen are present as the storage form in plants and animals respectively. The storage form is broken down into glucose units which serve to provide energy.
2. Structural role: Carbohydrates like cellulose, hemicellulose, and lignin provide a mechanical and protective function to the cell wall of plants. It also provide a definite shape to the plant cell. Chitin forms the part of the exoskeleton in insects and crustaceans.
Glycosaminoglycan like hyaluronic acid, heparin, chondroitin sulfate, and dermatan sulfate is a part of an extracellular matrix that plays a structural role in bacteria and animals only. It is a unit of acidic sugar and amino sugar.
3. Communication role: Carbohydrates are covalently bound to either protein or lipid to form glycoproteins or glycolipids. Glycoproteins act as a hormone (Thyroid-stimulating hormone (TSH) and erythropoietin), enzyme (Phosphatase, lipase, pepsinogen), receptor, integral membrane protein, mucins, and Cadherin is the major adhesion molecule.
Glycolipid acts as an enzyme, immunoglobins, secretory proteins, and membrane proteins.