NCERT Solutions for Class 11 Biology Chapter 16
|Chapter 16:||Digestion and Absorption|
Class 11 Biology Chapter 16 Solutions in English
NCERT Solutions for Class 11 Biology Chapter 16 in PDF form to free download is given below updated for new academic session 2021-2022. Download NCERT Books 2021-22 following the latest CBSE Syllabus. Offline Apps are also based on latest NCERT Solutions. If you have doubts, visit to discussion forum and ask your doubts.
Important Notes on Digestion and Absorption
1. Peristalsis: The involuntary movement of the gut by which the food bolus is pushed forward.
2. Deglutition: The process of swallowing of food bolus. It is partly voluntary and partly involuntary.
3. Ruminants: The herbivores animals (e.g., cow, buffalo etc.) which have symbiotic bacteria in the human of their stomach which synthesize enzymes to hydrolyse cellulose into monosaccharides.
4. Diarrhoea: The abnormal frequent discharge of semisolid or fluid faecal matter from the bowel.
5. Vomiting: The ejection of stomach contents through the mouth, caused by antiperistalsis.
6. Dysentery: Frequent watery stools often with blood and mucus and with pain, fever and causes dehydration.
DIFFERENT TYPES OF TEETH
1. Canine – for tearing
2. Incisors – for cutting
3. Premolars – for grinding
4. Molars – for churning and grinding
Basic Steps of Holozoic Nutrition
1. Ingestion: Intake of food.
2. Digestion: Breaking down of complex organic food materials into simpler, smaller soluble molecules.
3. Absorption and assimilation: Absorption of digested food into blood or lymph and its use in the body cells for synthesis of complex components.
4. Egestion: Elimination of undigested food as faeces
Important Terms related to Chapter 16
1. Chyme: The semifluid mass into which food is converted by gastric secretion and which passes from the stomach into the small intestine.
2. Gastric: Anything associated with stomach is given a prefix – gastric.
3. Proenzyme: The inactive forms of enzymes.
4. Sphincter: A flap like structure at various junctions of the alimentary canal which facilities one way traffic in the alimentary canal.
5. Bolus: The masticated food mixed with saliva.
6. Digestion: The process in alimentary canal by which the complex food is converted mechanically and biochemically into simple substances suitable for absorption and assimilation.
7. Food: A substance which on taken and digested in the body provides material for growth, repair, energy, and reproduction, resistance from disease or regulation of body processes.
8. Thecodont: The teeth embedded in the sockets of the jaw bone, e.g., in mammals.
Important Questions on 11th Biology Chapter 16
Why are villi present in the intestine and not in the stomach?
The mucosal wall of the small intestine forms millions of tiny finger-like projections known as villi. These villi increase the surface area for more efficient food absorption. Within these villi, there are numerous blood vessels that absorb the digested products of proteins and carbohydrates, carrying them to the blood stream. The villi also contain lymph vessels for absorbing the products of fat-digestion. From the blood stream, the absorbed food is finally delivered to each and every cell of the body.
What are the basic layers of the wall of alimentary canal?
The walls of the alimentary canal are made up of four layers. These are as follows: (i) Serosa is the outermost layer of the human alimentary canal. It is made up of a thin layer of secretory epithelial cells, with some connective tissues underneath. (ii) Muscularis is a thin layer of smooth muscles arranged into an outer longitudinal layer and an inner circular layer. (iii) Sub-mucosa is a layer of loose connective tissues, containing nerves, blood, and lymph vessels. It supports the mucosa. (iv) Mucosa is the innermost lining of the lumen of the alimentary canal. It is mainly involved in absorption and secretion.
How does bile help in the digestion of fats?
Bile is a digestive juice secreted by the liver and stored in the gall bladder. Bile juice has bile salts such as bilirubin and biliverdin. These break down large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. This process is known as emulsification of fats. Bile juice also makes the medium alkaline and activates lipase.
Describe the process of digestion of protein in stomach.
The digestion of proteins begins in the stomach and is completed in the small intestine. The digestive juice secreted in the gastric glands present on the stomach walls is called gastric juice. The food that enters the stomach becomes acidic on mixing with this gastric juice. The main components of gastric juice are hydrochloric acid, pepsinogen, mucus, and rennin. Hydrochloric acid dissolves the bits of food and creates an acidic medium so that pepsinogen is converted into pepsin. Pepsin is a protein- digesting enzyme. It is secreted in its inactive form called pepsinogen, which then gets activated by hydrochloric acid. The activated pepsin then converts proteins into proteases and peptides. Rennin is a proteolytic enzyme, released in an inactive form called prorennin. Rennin plays an important role in the coagulation of milk.
Given the dental formula of human beings.
The dental formula expresses the arrangement of teeth in each half of the upper jaw and the lower jaw. The entire formula is multiplied by two to express the total number of teeth. The dental formula for milk teeth in humans is:2102/2102×2=20 Each half of the upper jaw and the lower jaw has 2 incisors, 1 canine, and 2 molars. Premolars are absent in milk teeth. The dental formula for permanent teeth in humans is:2123/2123×2=32 Each half of the upper jaw and the lower jaw has 2 incisors, 1 canine, 2 premolars, and 3 molars. An adult human has 32 permanent teeth.
Bile juice contains no digestive enzymes, yet it is important for digestion. Why?
Bile is a digestive juice secreted by the liver. Although it does not contain any digestive enzymes, it plays an important role in the digestion of fats. Bile juice has bile salts such as bilirubin and biliverdin. These break down large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. This process is known as emulsification of fats. Bile juice also makes the medium alkaline and activates lipase.
What would happen if HCl were not secreted in the stomach?
Hydrochloric acid is secreted by the glands present on the stomach walls. It dissolves bits of food and creates an acidic medium. The acidic medium allows pepsinogen to be converted into pepsin. Pepsin plays an important role in the digestion of proteins. Therefore, if HCl were not secreted in the stomach, then pepsin would not be activated. This would affect protein digestion. A pH of about 1.8 is necessary for proteins to be digested. This pH is achieved by HCl.
Explain the term thecodont and diphyodont.
Thecodont is a type of dentition in which the teeth are embedded in the deep sockets of the jaw bone. Ankylosis is absent and the roots are cylindrical. Examples include living crocodilians and mammals. Diphyodont is a type of dentition in which two successive sets of teeth are developed during the lifetime of the organism. The first set of teeth is deciduous and the other set is permanent. The deciduous set of teeth is replaced by the permanent adult teeth. This type of dentition can be seen in humans.
Name different types of teeth and their number in an adult human.
There are four different types of teeth in an adult human. They are as follows: Incisors The eight teeth in the front are incisors. There are four incisors each in the upper jaw and the lower jaw. They are meant for cutting. Canines The pointy teeth on either side of the incisors are canines. They are four in number, two each placed in the upper jaw and the lower jaw. They are meant for tearing. Premolars They are present next to the canines. They are eight in number, four each placed in the upper jaw and the lower jaw. They are meant for grinding. Molars They are present at the end of the jaw, next to the premolars. There are twelve molars, six each placed in the upper jaw and the lower jaw. Hence,the dental formula in humans=2123/2123×2=32 This means each half of the upper jaw and the lower jaw has 2 incisors, 1 canine, 2 premolars, and 3 molars. Hence, an adult human has 32 permanent teeth.
What are the functions of liver?
Liver is the largest and heaviest internal organ of the body. It is not directly involved in digestion, but secretes digestive juices. It secretes bile which plays a major role in the emulsification of fats.