Zoology · Class 12 Science
Ch 1Digestion and Absorption — Class 12 Zoology, concept-first.
The food we eat is a mixture of large, complex biomolecules -- carbohydrates, proteins and fats -- along with vitamins, minerals and water. The body cannot use these large molecules directly in the form we swallow them.
Key concepts
Hover a concept to preview it and jump to its most relevant Q&A.
Digestive Enzymes
Digestion depends on a sequence of enzymes, most secreted as inactive proenzymes that are switched on only where they are needed, so they do not digest the tissues that make them.
Most relevant Q&A
- Choose the correct answer among the following: (a) Gastric juice contains (i) pepsin, lipase and rennin (ii) trypsin, lipase and rennin (iii…Free
- Match column I with column II Column I: (a) Bilirubin and biliverdin; (b) Hydrolysis of starch; (c) Digestion of fat; (d) Salivary gland Col…Free
- Describe the digestive role of chymotrypsin. Which two other digestive enzymes of the same category are secreted by its source gland?Preview
- How are polysaccharides and disaccharides digested?Preview
Chapter contents
The NCERT structure, section by section. Open a section to see its questions, then read the concept-first solution.
Digestive System
The food we eat is a mixture of large, complex biomolecules -- carbohydrates, proteins and fats -- along with vitamins, minerals and water.
Alimentary Canal
The alimentary canal opens to the outside at the mouth, leading into the buccal (oral) cavity, which houses the teeth and a muscular tongue.
Digestive Glands
Saliva is produced mainly by three pairs of salivary glands situated just outside the buccal cavity and opening their secretions into it: the parotids near the cheek, the sub-maxillary (sub-mandibular…
Digestion of Food
In the buccal cavity, the teeth and tongue, helped by saliva, chew (masticate) and thoroughly mix the food. Mucus in the saliva binds the chewed particles into a rounded mass called a bolus.
Absorption of Digested Products
Absorption is the process by which the end products of digestion cross the intestinal mucosa into the blood or the lymph. Different substances use different routes:
Disorders of Digestive System
Inflammation of the intestinal tract is the most common digestive ailment. It can be caused by bacterial or viral infection, or by intestinal parasites such as tapeworm, roundworm, threadworm, hookwor…
Exercises
+−Show 15 questionsHide questions15 questions
- Q1Choose the correct answer among the following: (a) Gastric juice contains (i) pepsin, lipase and rennin (ii) trypsin, lipase and rennin (iii…Free
- Q2Match column I with column II Column I: (a) Bilirubin and biliverdin; (b) Hydrolysis of starch; (c) Digestion of fat; (d) Salivary gland Col…Free
- Q3Answer briefly: (a) Why are villi present in the intestine and not in the stomach? (b) How does pepsinogen change into its active form? (c)…Free
- Q4State the role of pancreatic juice in digestion of proteins.Preview
- Q5Describe the process of digestion of protein in stomach.Preview
- Q6Give the dental formula of human beings.Preview
- Q7Bile juice contains no digestive enzymes, yet it is important for digestion. Why?Preview
- Q8Describe the digestive role of chymotrypsin. Which two other digestive enzymes of the same category are secreted by its source gland?Preview
- Q9How are polysaccharides and disaccharides digested?Preview
- Q10What would happen if HCl were not secreted in the stomach?Preview
- Q11How does butter in your food get digested and absorbed in the body?Preview
- Q12Discuss the main steps in the digestion of proteins as the food passes through different parts of the alimentary canal.Preview
- Q13Explain the term thecodont and diphyodont.Preview
- Q14Name different types of teeth and their number in an adult human.Preview
- Q15What are the functions of liver?Preview