The food we eat undergoes mechanical and chemical digestion before getting absorbed in the blood stream. This digestion of food is carried at various sites such as mouth, stomach, small intestine and to a less extent in large intestine with the help of enzymes.
a.) The mouth is the first site of chemical digestion. It produces saliva which has amylase enzyme which acts on carbohydrate content any breaks down then in smaller molecules. It carries a few digestions only.
b.) Stomach is the site where protein digestion begins at first by the enzyme secreted in the stomach known as pepsin. Pepsin works on proteins by breaking the peptide bonds which holds the molecule together.
c.) Partially digested food enters small intestine through stomach. It is the principal site where digestion of different biomolecules occur. It secretes a variety of digestive enzymes which acts on partially digested food and get digested and absorbed. One such enzyme is maltase which act on partially digested carbohydrates and break down them into glucose units by breaking glyosidic bonds.
d.) Small intestine is the major site of protein digestion by secreting peptidase which acts on proteins and peptides and break them into amino acids.
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