This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Absorption of Digested Products”.
1. Which of the following is an active enzyme in the pancreas?
Explanation: The inactive enzymes of the pancreas are trypsinogen, procarboxypeptidase and chymotrypsinogen. The other pancreatic enzymes include amylases, lipases and nucleases.
2. Which of the following enzymes activate trypsinogen?
Explanation: Trypsinogen is activated by an enzyme, enterokinase, secreted by the intestinal mucosa into active trypsin, which in turn activates the other enzymes in the pancreatic juice.
3. Which of the following is not present in bile?
Explanation: Nucleases are not present in the bile as this enzyme is the secretion of the pancreas. The bile released into the duodenum contains bile pigments like bilirubin and biliverdin, bile salts, cholesterol and phospholipids. No enzyme is present in the bile juice.
4. Which secretions constitute the intestinal juice?
a) Bile juice
b) Pancreatic juices
c) Stomach secretions
d) Secretions of brush border cells and goblet cells
Explanation: The intestinal mucosal epithelium has goblet cells which secrete mucus. The secretions of the brush border cells of the mucosa along with the secretions of the goblet cells constitute the intestinal juice or succus entericus.
5. Bile protects the intestinal mucosa from acid and alkaline medium.
Explanation: The mucus along with the bicarbonates released from the pancreas protects the intestinal mucosa from acid as well as provide an alkaline medium for enzymatic activities. Submucosal glands also help in this.
6. What are peptones?
a) Partially hydrolysed proteins
b) Completely hydrolysed proteins
c) Incompletely ligase proteins
d) Hydrolysed proteins
Explanation: Peptones are partially hydrolysed proteins. Proteins, proteoses and peptones in the chyme after reaching the small intestine are acted upon by the proteolytic enzymes of the pancreatic juice.
7. In the small intestine, carbohydrates are broken down into which of the following?
Explanation: In the small intestine, carbohydrates in the chyme are hydrolysed by pancreatic amylase into disaccharides. Fats are broken down by lipases with the help of bile into di and monoglycerides.
8. Which of the following is not a product of the breakdown of nucleic acids?
d) Nitrogen base
Explanation: The nucleases in the pancreatic juice acts in nucleic acids to form nucleotides and nucleosides which are further broken down by nucleosidases to sugars and nitrogen bases.
9. Where does the breakdown of bio-macromolecules take place?
Explanation: The breakdown of bio-macromolecules occurs in the duodenum region of the small intestine. The simple substances thus formed are absorbed in the jejunum and ileum regions of the small intestine.
10. No significant digestive activity occurs in the large intestine.
Explanation: No significant digestive activity occurs in the large intestine. The only known function of the large intestine is absorption of water, minerals and certain drugs. The inner layer of large intestine also secretes some amount of mucus which helps to bind the waste particles together.
11. Which valve prevents the backflow of faeces into the ileum?
a) Ileo-caecal valve
b) Pyloric sphincter
c) Sphincter of Oddi
d) Cardiac sphincter
Explanation: The undigested, unabsorbed substances are called faeces which enter into the caecum of the large intestine through the ileocaecal valve, which prevents the backflow of the faecal matter.
12. Where are the faeces stored till defaecation?
Explanation: The faeces are temporarily stored in the rectum till defaecation. The activities of the gastrointestinal tract are under neural and hormonal control for proper coordination of different parts.
13. Gastric and intestinal secretions are stimulated by which of the following?
a) Neural signals
b) External stimulus
c) Internal stimulus
d) Excitation of cells
Explanation: gastric and intestinal secretions are stimulated by neural signals. The muscular activities of different parts of the alimentary canal can also be moderated by neural mechanism, both local and through CNS.
14. What is the ultimate form of energy?
Explanation: Heat is the ultimate form of energy and that is why the energy requirements of animals, and the energy content of food, are expressed in terms of a measure of heat energy.
15. What is meant by 1 calorie?
a) Amount of heat energy required to raise the temperature of 1 kg of water
b) Amount of heat energy required to raise the temperature of 1-tonne water
c) Amount of heat energy required to raise the temperature of 1 mg water
d) Amount of heat energy required to raise the temperature of 1 g water
Explanation: Heat energy is often measured as calorie (cal) or joule (J), which is the amount of heat energy required to raise the temperature of 1 g of water by 1° C.
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