Question

Which is the first enzyme to mix with food in the digestive tract?
(a) Pepsin
(b) Cellulose
(c) Amylase
(d) Trypsin

Answer 1

The digestion of food itself starts in the mouth due to the enzyme present in the saliva that helps it the breakdown of starch. It is also known as ptyalin.

Complete answer:
The buccal cavity performs two functions, mastication of food and facilitation of swallowing. The teeth and the tongue with the help of saliva masticates and mixes up the food thoroughly. Mucus in saliva helps in the lubricating and adhering of the masticated food particles into the bolus.
The saliva secreted in oral cavity contains electrolytes (${ Na }^{ + },\quad { K }^{ + },\quad { Cl }^{ - }\quad ,\quad { HCO }_{ 3 }^{ - }$) and enzymes, salivary amylase (ptyalin) and lysozyme. The chemical process of digestion starts in the oral cavity. It is done by the hydrolytic action of the carbohydrates splitting enzymes, the salivary amylase. The amylase is the first enzyme to mix with the food in the digestive tract.
$\underset { (Polysaccharide) }{ Starch } \xrightarrow [ pH\quad 6.8 ]{ Salivary\quad amylase } \underset { (Disaccharide) }{ Maltose }$
The masa of bolus is then pushed down through the pharynx into the esophagus. This process is called swallowing or deglutition.
So, the answer is, ‘Amylase.’

Note: - Salivary amylase is absent from the saliva of many mammals like cows, buffaloes, and predatory animals like lions and tigers. - Amylase hydrolyzes about 30% of starch into disaccharide-maltose at optimum pH of 6.8. - The lysozyme present in saliva acts as an antibacterial agent that prevents bacterial infections. - Ptyalin is a type of $\alpha$ amylase which is also secreted by the pancreas in pancreatic juices.