Question

Which one of the following statements is true regarding digestion and absorption of food in humans?

• A. Chylomicrons are small lipoprotein particles that are transported from intestine into blood capillaries.
• B. About 60% of starch is hydrolyzed by salivary amylase in our mouth.
• C. Oxyntic cells in our stomach secrete the proenzyme pepsinogen.
• D. Fructose and amino acids are absorbed through intestinal mucosa with the help of carrier ions like $N{a}^{+}$

Answer 1

The correct option is D Fructose and amino acids are absorbed through intestinal mucosa with the help of carrier ions like $N{a}^{+}$

Digestion of starch begins in mouth by the action of salivary amylase or ptyalin which breaks starch into dextrin and maltose. However majority of starch molecules are digested in intestine by the action of pancreatic and intestinal juices. The stomach is primarily concerned with digestion of proteins with the help of enzyme pepsin. The enzyme pepsin is secreted in the inactive form pepsinogen by peptic cells. The hydrochloric acid secreted by oxyntic or parietal cells brings about activation of pepsinogen to pepsin. Absorption is the process by which the end products of digestion pass through the intestinal mucosa into the blood or lymph. Small amounts of monosaccharides like glucose, amino acids and some of electrolytes like chloride ions are generally absorbed by simple diffusion. The passage of these substances into the blood depends upon the concentration gradients. However, some of the substances like fructose and some amino acids are absorbed with the help of the carrier ions like Na+. This mechanism is called the facilitated transport. Fatty acids and glycerol being insoluble, cannot be absorbed into the blood. They are first incorporated into small droplets called micelles which move into the intestinal mucosa. They are re-formed into very small protein coated fat globules called the chylomicrons which are transported into the lymph vessels (lacteals) in the villi. These lymph vessels ultimately release the absorbed substances into the blood stream.