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Important Questions Class 11 Biology Chapter 16 Digestion Absorption

Food is one of the most fundamental requirements for living entities to survive. In humans, the digestive system consists of the digestive glands and the alimentary canal. Food provides all the minerals, vitamins and organic compounds that are required to grow and repair the body. Water plays a vital role in the digestion process and prevents the body from entering a state of dehydration. Biomolecules in food cannot be utilized by our body and hence need to be broken down into simpler substances in the digestive system. This process is known as digestion.

Q.1. What is the food called when food blends completely with acidic gastric juices of the stomach by the churning movements of the muscular wall. A.1.  The food stays in the stomach for 4-5 hours during which it gets blended completely with the acidic gastric juice present in the stomach through churning movements of the muscular walls. At this point, the food is referred to as chyme. Q.2. Name the tissue or cells that secrete the enzyme enterokinase, which activates Trypsinogen. How is it activated? A.2.  The enzyme enterokinase activates trypsinogen to trypsin. The enzyme is secreted by the intestinal mucosa. Q.3. Where in the alimentary canal, absorption of water, alcohol and simple sugars take place? A.3.  In the wall of the stomach. Q.4. List the enzymes that are involved in the breakdown of nucleotides into bases and sugars. A.4.  Nucleotidases and nucleosidases. Q.5. What is digestion? A.5.  Digestion is the process of converting complex food substances into simpler substances that can be absorbed through mechanical and biochemical methods. Q.6. Name the type of teeth-attachment to the jawbones wherein each tooth is embedded in a socket of jawbones. A.6.  The type of teeth is called Codont. Q.8. Which glands are associated with the alimentary canal? A.8. The salivary glands, the liver and the pancreas, are the lists of glands, associated with the alimentary canal. Q.9. What is the Pancreas? A.9. The pancreas is an abdominal organ located in the stomach,  behind the abdomen and surrounded by spleen, liver and small intestine. It is a vital part of the  human digestive system  and is responsible for regulating blood sugar levels. Q.10. What is the Liver? A.10.  The liver is the largest organ located in the right upper quadrant of the abdomen and below the diaphragm. It plays a vital role in the digestion of fats, metabolism of carbohydrates and formation of bile. Q.11.What are the functions of bile? A.11. Bile is a dark yellowish-green or brown colour fluid produced by the liver and stored within the gallbladder. It comprises organic molecules such as bile acids, slats, bilirubin and cholesterol, and water. Q.12.Describe the process of elimination. A.12. Elimination is a final process of digestion. In this process, the food residues that cannot be digested or absorbed are excreted or egested from the body as semi-solid faeces. Q.13.What is constipation? A.13. Constipation is defined as the digestive disorders, associated with the irregular and difficult bowel movement characterized by hardened faeces. Q.14. Where does the process of digestion take place? A.14. The process of digestion begins from the mouth and is then carried on to the stomach, to the small intestine, large intestine and then to the anus. Q.15. What is the Alimentary Canal? A.15. The alimentary canal is the pathway by which food enters our body. It is a tube-like structure, which starts from the mouth and ends at the large intestine.

Q.1. What is the pancreas? What are the main secretions of the pancreas,which aids in digestion? A.1.  The pancreas is a gland that has endocrine and exocrine parts required in producing hormones and digestive  enzymes . The inactive enzymes involved in digestion and secreted by pancreas are as follows:

Q.2. Write the organs of the human alimentary canal. Mention the major digestive glands along with their locations A.2.  The alimentary canal consists of the anterior opening – the pharynx, buccal cavity, mouth, oesophagus, stomach, small intestine, large intestine, and anus. The digestive glands are -:

Q.3. What is the significance of the gall bladder? Write the consequence if it stops functioning or is removed. A.3.  The gall bladder is a pear-shaped sac-like composition, which is connected to the dorsal surface of the liver via connective tissue. The hepatic cells of the liver secrete bile, which moves through the hepatic ducts gets accumulated in the gall bladder. If the gall is removed or turns non-functional, the bile would continuously run from the liver into the intestine, without being concentrated enough as the bile originated in the gall bladder. A low-fat diet is suggested even though the body adapts as the digestion of fat is seemingly decreased after gall bladder is removed. Q.4. Write the three major types of cells present in the gastric glands. List their secretions. A.4.  Gastric glands are present in the mucosa of the stomach. The three major cells are:

Q.5. How is the intestinal mucosa guarded against the acidic food entering from the stomach? A.5.  The highly concentrated hydrochloric acid rich food is prevented from excoriation because of the mucus secreted by the goblet cells along with the bicarbonates, which are significant in lubrication and protection of the mucosal epithelium. Q6. What is the difference between digestion and absorption? A.6. Digestion is the process of crushing or digesting large and insoluble food molecules into smaller and soluble molecules for easy absorption into the bloodstream. Absorption is the mechanical and digestive processes of absorbing or assimilation of substances into the cells or across the tissues and organs through the process of diffusion or osmosis. Q.7. What is the process of digestion and absorption of carbohydrates? A.7.  Carbohydrates consist of monosaccharides, disaccharides and complex carbohydrates, including starch, glycogen, and fibre. The digestion and absorption of carbohydrates begin with the breakdown of disaccharides and complex carbohydrates into monosaccharides for absorption, and the process begins from the in the mouth via the process of chewing and with the release of enzyme amylase from the salivary glands. The digestion and absorption of carbohydrates are completed in the small intestine, with the help of amylase secreted by the pancreas. The below diagram explains the process and the different enzymes involved in the digestion and absorption of carbohydrates. Q.8. What is digestion, mechanical digestion and chemical digestion? A.8. Digestion –It is the process of converting large insoluble food molecules into small, soluble and absorbable forms. The complete process of digestion occurs in a sequential manner by a union of both methods:

Q.9. What are enzymes? A.9. Enzymes can be defined as the biological molecules or biological catalysts, which significantly speed up the rate of digestion by lowering the activation energy. Enzymes also facilitate the digestion of certain molecules to occur independently, in distinct locations, at body temperatures and at sufficient speeds. Q.10. What is indigestion? A.10. Indigestion, also known as dyspepsia, is a medical term, which describes the pain and discomfort in the upper abdomen. It is a type of a functional disorder, caused by the abnormal functioning of the digestive system or gastrointestinal organs.

Q.1. Write the changes occurring in the passage through the  alimentary canal  when a person has ingested roti and dal as part of his meal. A.1.  The following are the changes:

Q.2. Write the mechanism of absorption. A.2.  It is the phenomenon through, which the end products of digestion pass via the intestinal mucosa into the lymph or blood, which is carried out through active, passive or facilitated transport means. Through simple diffusion, little quantities of monosaccharides such as amino acids, glucose and few electrolytes such as chloride ions are absorbed. The concentration gradients decide the passage of these substances into the blood. But amino acids and glucose are absorbed with the aid of carrier proteins and is referred to as facilitated transport. Water transport is dependant on the osmotic gradient. Active transport requires energy as it takes place against the concentration gradient. Through this mechanism, several monosaccharides such as glucose, nutrients such as amino acids, electrolytes such as Na+ are absorbed into the blood. Q.3. What is the significance of hepato-pancreatic complex in digesting protein, carbohydrate and fat components of food? A.3.  The pancreatic and bile duct secretes bile and pancreatic juices into the duodenum through the common duct – the hepato-pancreatic duct, which is shielded by a sphincter of Oddi. The pancreatic juice includes inactive enzymes –

The effect of hepato-pancreatic secretion on the digestion of fats, proteins, and carbohydrates are as follows:

Q.4. How does digestion occur in the buccal cavity? Explain with the arrangement of teeth. A.4.  The buccal cavity has two important functions –

The tongue and the teeth with aid of saliva, masticate and blend the food completely. The mucus present in saliva helps in lubricating and holding the masticated food particles into a bolus. The bolus is further passed into the pharynx and down the oesophagus by deglutition or swallowing. The bolus moves through successive waves of contractions of the muscles down the oesophagus, this movement is known as peristalsis. Q.5. Define the following terms–Bolus, Mastication and Digestive Enzymes. A.5. Bolus–  It is round, ball-shaped and a mixture of a chewed food formed by the combination of food and saliva in the mouth or alimentary canal. Mastication–  It is the act of chewing the food. In this process, the food particles are broken down into smaller and soluble particles for ease of swallowing. This process occurs inside the oral cavity, including the teeth, tongue and the cheek. Digestive Enzyme-  They are the group of enzymes found in the digestive tracts and are secreted predominantly by the pancreas and other organs including the salivary gland, stomach and in the lining of the gastrointestinal tract.  Digestive Enzymes   play a key role in the process of chemical digestion.

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