Digestion and Absorption Test - 25

Hint: The process of digestion begins in the mouth with the intake of food.

Carbohydrate digestion starts in mouth by the enzyme amylase present in the saliva. Food enters into the stomach where the complex protein is digested into the simple protein of dipeptides by pepsin. In small intestine food is further digested in the presence of pancreatic juice and bile. Dipeptides are converted into the amino acids by trypsin and lipids are emulsified and digested by lipase and bile.

• The digestion process of polysaccharides such as starch will begin in the mouth where it is hydrolyzed by salivary amylase. Carbohydrase enzymes break down starch into sugars.
• Protein digestion occurs in the stomach and the duodenum through the action of three main enzymes: pepsin, secreted by the stomach, and trypsin and chymotrypsin, secreted by the pancreas.
•  Lactose is normally broken down by an enzyme called lactase, which is produced by cells in the lining of the small intestine.
  So, the correct answer is option B. 

Trypsin is a protein-splitting enzyme, produced in the pancreas as an inactive protease trypsinogen. When it is secreted in the small intestine, it is activated by the intestinal enteropeptidase. Activated trypsin catalyses proteins into smaller peptides.

The main function of the large intestine is the absorption of water from the undigested food. This is done to minimize the loss of water from the body.

Pancreatic juice contains trypsinogen, which is inactive zymogen form of trypsin which is activated by enteropeptidase (also called as enterokinase) and acts on proteins.
Fats need to be emulsified before digestive enzymes can act on them because fats are not soluble in water. Fats or lipids are acted on by lipases.

 A layer of mucus along the inner walls of the stomach is vital to protect the cell linings of that organ from the highly acidic environment within it.

Correct Option: B
Explanation:

• Amylase is the enzyme that catalyses the hydrolysis of starch into simple sugars.
• So if salivary amylase is lacking in saliva, the breakdown of starch is affected. 
• Other phenomena such as protein breakdown to amino acids by protease enzyme and fat breakdown by bile in the small intestine. Whereas vitamins are absorbed by the small intestine.
• Hence, if salivary amylase is lacking in the saliva, then in the mouth starch will not break down in sugar.

All of these growth, transport, nutrition, and synthesis are important characteristics of living systems.

• Digestion starts from the mouth and ends at large intestine. When the food enters mouth (ingestion), it is broken into small pieces by the teeth and acted upon by salivary amylase. 
• Then it travels down the oesophagus to the stomach, where digestive enzymes from the pancreas, gall bladder, liver and duodenum further digest it.
• Assimilation of nutrients occurs at small intestine and absorption of water and other substances happen at the large intestine before it is egested or excreted. 
• Thus, the correct answer is option D.