NCERT MOST IMPORTANT QUESTIONS CLASS – 11 | BIOLOGY IMPORTANT QUESTIONS | CHAPTER -16 | DIGESTION AND ABSORBTION | EDUGROWN |

In This Post we are  providing Chapter-16 DIGESTION AND ABSORBTION NCERT MOST IMPORTANT QUESTIONS for Class 11 BIOLOGY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTIONS ON DIGESTION AND ABSORBTION

Q1. Correct the statement given below by the right option shown in the bracket against them.
a. Absorption of amino acids and glycerol takes place in the (small intestine/ large intestine).
b. ‘The faeces in the rectum initiate a reflex causing an urge for its removal, (neural /hormonal)
c. Skin and eyes turn yellow in infection, (liver/stomach)
d. Rennin is a proteolytic enzyme found in gastric juice in (infants/adults).
e. Pancreatic juice and bile are released through (intestinepancreatic/ hepato-pancreatic duct).
f. Dipeptides, disaccharides and glycerides are broken down into simple substances in region of small intestine, (jejunum/duodenum)
Ans: a. Absorption of amino acids and glycerol takes place in the small intestine.
b. The faeces in the rectum initiate a neural reflex causing an urge for its removal.
c. Skin and eyes turn yellow in infection of liver. .
d. Rennin is a proteolytic enzyme found in gastric juice in infants.
e. Pancreatic juice and bile are released through hepato-pancreatic duct.
f. Dipeptides, disaccharides and glycerides are broken down into simple substances in duodenum region of small intestine.

Q2. What are three major types of cells found in the gastric glands? Name their secretions.
Ans: The mucosa of stomach has gastric glands. Gastric glands have three major types of cells namely
(i) mucus neck cells which secrete mucus;
(ii) peptic or chief cells which secrete the proenzyme pepsinogen; and
(iii) parietal or oxyntic cells which secrete HC1 and intrinsic factor (factor essential for absorption of vitamin B12).

Q3. How are the activities of gastro-intestinal tract regulated?
Ans: The activities of the gastro-intestinal tract are under neural and hormonal control for proper coordination of different parts. The sight, smell and/or the presence of food in the oral cavity can stimulate the secretion of saliva. Gastric and intestinal secretions are also, similarly, stimulated by neural signals. The muscular activities of different parts of the alimentary canal can also be moderated by neural mechanisms, both local and through CNS. Hormonal control of the secretion of digestive juices is carried out by local hormones produced by the gastric and intestinal mucosa.

Q4. Distinguish between constipation and indigestion. Mention their major causes.
Ans: Constipation: In constipation, the faeces are retained within the rectum as the bowel movements occur irregularly.
Indigestion: In this condition, the food is not properly digested leading to a feeling of fullness. The causes of indigestion are inadequate enzyme secretion, anxiety, food poisoning, over eating, and spicy food.

Q5. Describe the enzymatic action on fats in the duodenum.
Ans: In the duodenum fats are broken down by pancreatic lipases with the help of bile into di- and monoglycerides.

Q6. A person had roti and dal for his lunch. Trace the changes in those during its passage through the alimentary canal.
Ans: The process of digestion is accomplished by mechanical and chemical processes. The buccal cavity performs two major functions, mastication of food and facilitation of swallowing. The teeth and the tongue with the help of saliva masticate and mix up the food thoroughly. Mucus in saliva helps in lubricating and adhering the masticated food particles into a bolus. The bolus is then conveyed into the pharynx and then into the oesophagus by swallowing or deglutition. The bolus further passes down through the oesophagus by successive waves of muscular contractions called peristalsis. The gastro-oesophageal sphincter controls the passage of food into the stomach. The saliva secreted into the oral cavity contains electrolytes and enzymes, salivary amylase and lysozyme. The chemical process of digestion is initiated in the oral cavity by the hydrolytic action of the carbohydrate splitting enzyme, the salivary amylase. About 30% of starch is hydrolysed here by this enzyme (optimum pH 6.8) into a disaccharide – maltose.
• The stomach stores the food for 4-5 hours. The food mixes thoroughly with the acidic gastric juice of the stomach by the churning movements of its muscular wall and is called the chyme. The proenzyme pepsinogen, on exposure to hydrochloric acid gets converted into the active enzyme pepsin, the proteolytic enzyme of the stomach. Pepsin converts proteins into proteoses and peptones (peptides).
• The bile, pancreatic juice and the intestinal juice are the secretions
released into the small intestine. Pancreatic juice and bile are released through the hepato-pancreatic duct. The pancreatic juice contains inactive enzymes—trypsinogen, chymotrypsinogen, procarboxypeptidases,
amylases, lipases and nucleases. 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.
Proteins proteoses and peptones (partially hydrolysed proteins) in the chyme reaching the intestine are acted upon by the proteolytic enzymes of pancretic juice as given below.

Q7. What are the various enzymatic types of glandular secretions in our gut helping digestion of food? What is the nature of end products obtained after complete digestion of food?
Ans: Enzymatic types of glandular secretions in our gut:
a. Salivary glands: Saliva is mainly produced by three pairs of salivary glands, the parotids (cheek), the sub-maxillary/sub-mandibular (lower jaw) and the sublinguals (below the tongue). These glands situated just outside the buccal cavity secrete salivary juice into the buccal cavity.
b. Gastric glands: The mucosa of stomach has gastric glands. Gastric glands have three major types of cells namely
(i) mucus neck cells which secrete mucus;
(ii) peptic or chief cells which secrete the proenzyme pepsinogen; and
(iii) parietal or oxyntic cells which secrete HC1 and intrinsic factor (factor essential for absorption of vitamin B12).
c. The bile, pancreatic juice and the intestinal juice are the secretions
released into the small intestine. Pancreatic juice and bile are released through the hepato-pancreatic duct. The pancreatic juice contains inactive enzymes—trypsinogen, chymotrypsinogen, procarboxypeptidases,
amylases, lipases and nucleases. 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. The bile released into the duodenum contains bile pigments (bilirubin and biliverdin), bile salts, cholesterol and phospholipids but no enzymes.

Q8. Discuss mechanisms of absorption.
Ans: Mechanisms of absorption: Absorption is the process by which the end products of digestion pass through the intestinal mucosa into the blood or lymph. It is carried out by passive, active or facilitated transport mechanisms. Small amounts of monosaccharides like glucose, amino acids and some 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 substances like glucose and amino acids are absorbed with the help of carrier proteins. This mechanism is called the facilitated transport.
Transport of water depends upon the osmotic gradient. Active transport occurs against the concentration gradient and hence requires energy. Various nutrients like amino acids, monosaccharides like glucose, electrolytes like Na+ are absorbed into the blood by this mechanism.

Q9. Discuss the role of hepato-pancrdatic complex in digestion of carbohydrate, protein and fat components of food.
Ans: The bile, pancreatic juice and the intestinal juice are the secretions released into the small intestine. Pancreatic juice and bile are released through the hepato-pancreatic duct. The pancreatic juice contains inactive enzymes— trypsinogen, chymotrypsinogen, procarboxypeptidases, amylases, lipases and nucleases. 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.
The bile released into the duodenum contains bile pigments (bilirubin and biliverdin), bile salts, cholesterol and phospholipids but no enzymes. Bile helps in emulsification of fats, i.e., breaking down of the fats into very small micelles. Bile also activates lipases.
Proteins proteases and peptones (partially hydrolyzed proteins) in the chime reaching the intestine are acted upon by the proteolytic enzymes of pancreatic juice as given below:

Q10. Explain the process of digestion in the buccal cavity with a note on the arrangement of teeth.

Ans: The process of digestion in the buccal cavity: The buccal cavity performs two major functions, mastication of food and facilitation of swallowing. The teeth and the tongue with the help of saliva masticate and mix up the food thoroughly. Mucus in saliva helps in lubricating and adhering the masticated food particles into a bolus. The bolus is then conveyed into the pharynx and then into the oesophagus by swallowing or deglutition. The bolus further passes down through the oesophagus by successive waves of muscular contractions called peristalsis. The gastro-oesophageal sphincter controls the passage of food into the stomach. The saliva secreted into the oral cavity contains electrolytes and enzymes, salivary amylase and lysozyme. The chemical process of digestion is initiated in the oral cavity by the hydrolytic action of the carbohydrate splitting enzyme, the salivary amylase. About% of starch is hydrolysed here by this enzyme (optimum pH 6.8) into a disaccharide—maltose. Lysozyme present in saliva acts as an antibacterial agent that prevents infections.