Question

Which of the following are chiefly digested in the stomach?
A. Protein
B. Carbohydrate
C. Lipids
D. Fats

Answer 1

Hint: Digestion is the break-up into small water-soluble food molecules of large insoluble food molecules so that they can be absorbed into the plasma of the watery blood. These smaller substances of certain species are ingested into the bloodstream through the small intestine.

Complete Answer:
The digestion process comprises the following steps:
(1) Ingestion: Most animals, with the aid of the mouth or tongue, catch the prey/food with the intake of food.

(2) Mastication: The process occurs with the aid of teeth in the buccopharyngeal cavity of mammals. Food is broken down into small pieces during this process, which increases its surface area. In frog teeth, chewing is not intended, but prevents prey from escaping from the mouth.

(3) Deglutition/swallowing: The passage of food to the oesophagus/stomach from the bucco-pharyngeal cavity. In mammals, the chewed food bolus is produced in the buccopharyngeal cavity that slides easily into the oesophagus. It is a mechanism of voluntary reflex. Peristalsis is an alternate contraction and the relaxation of the circular and longitudinal muscles causes the contraction wave due to which the food in the lumen of the food canal travels from the front to the backward direction.This phenomenon is known as peristalsis. It is also present in vas deferens, ureter etc. in addition to food canals. Peristalsis is highest in the oesophagus and lowest in the rectum.

Digestion in the buccopharyngeal cavity: Only starch, which is 5% of the total food or 20-30 carbohydrates, is digested in the buccopharyngeal cavity of mammals.

Digestion in the stomach: In the stomach, proteins are primarily digested.

Digestion in the small intestine: All three elements of carbohydrates, proteins and fats are digested in the small intestine using pancreatic and intestinal gland-secreted enzymes.

The correct Answer is option (A)Proteins.

Note: Hormonal control of digestion : Nervous and endocrine systems organise digestive tract activities. The sight and smell of food activates the nervous system, which causes large quantities of saliva to be generated by the salivary glands, gastrin to be released by the stomach and intestine to produce intestinal hormones. Sequential order is provided by other hormones. They are all polypeptide hormones.