Digestion refers to the mechanical and chemical breakdown of food.
Explanation:
Digestion begins with the mechanical breakdown of the ingested food in the mouth by chewing or mastication of food with teeth and movement of the lower jaw.
This breaks the larger food particles into smaller particles which then mix and churn with the saliva to form a bolus.
The bolus of food moves through the alimentary canal by mechanical peristaltic movement and passes through various digestive organs like stomach, pancreas, duodenum, liver, small intestines and large intestines.
Chemical breakdown of food involves breaking down of complex molecules present in the undigested bolus into simple molecules in the form of nutrients to be readily absorbed by the cells.
During this course, enzymes act upon the complex food molecules and enzyme-mediated hydrolytic reactions takes place which converts complex polysaccharides and starch into simple monosaccharides, proteins into simpler amino acids, fats into simple glycerides or fatty acids.
Biochemicals like acids present digestive juices like gastric juice and bile also facilitates chemical breakdown of food.
