CBSE Class 12 Chemistry Biomolecules Worksheet Set B

Question. Which one of the following is a monosaccharide :
starch, maltose, fructose, cellulose
Answer. Fructose is a monosaccharide because it cannot be hydrolysed to simpler polyhydroxy aldehydes or ketones.

Question. Write the name of two monosaccharides obtained on hydrolysis of lactose sugar.
Answer. Lactose on hydrolysis gives β-D-glucose and β-D-galactose.

Question. Write the name of the vitamin whose Deficiency causes bleeding of gums. 
Answer. Vitamin C

Question. Write the structural difference between starch and cellulose.
Answer. The basic structural difference between starch and cellulose is of linkage between the glucose units. In starch, there is a-D-glycosidic linkage. Both the components of starch-amylose and amylopectin are polymer of a-D-glucose. On the other hand, cellulose is a linear polymer of b-D-glucose in which C₁ of one glucose unit is connected to C₄ of the other through β-D-glycosidic linkage.

Question. Which one of the following is a disaccharide :
Starch, Maltose, Fructose, Glucose?
Answer.  Maltose is a disaccharide as it consists of two a-D-glucose units.

Question. Define the following term :
Polysaccharides 
Answer. Carbohydrates which yield a large number of monosaccharide units on hydrolysis are called polysaccharides.

Question. Why Vitamin C cannot be stored in our body?
Answer. Vitamin C is soluble in water and regularly excreted in urine and hence cannot be stored in body.

Question. Deficiency of which vitamin causes nightblindness?
Answer. Vitamin A

Question. Which of the two components of starch is water soluble?
Answer. Amylose is water soluble and amylopectin is insoluble in water.

Question. What is meant by ‘reducing sugars’?
Answer. Carbohydrates which reduce Tollen’s reagent are reducing sugars. All monosaccharides, aldoses or ketoses are reducing sugars.

Question. Define the following term :
Vitamins
Answer. Organic compounds required in the diet in small amounts to perform specific biological functions for normal maintainance of optimum growth and health of the organism are called vitamins.

Question. Why are vitamin A and vitamin C essential for us? 
Answer. The deficiency of vitamin A leads to xerophthalmia and night blindness. The deficiency of vitamin C leads to scurvy.

Question. Write the name of vitamin whose Deficiency causes bone deformities in children.
Answer. Vitamin D

Question. What are the products of hydrolysis of sucrose?
Answer. Glucose and fructose.

Question. What is the structural feature characterising reducing sugar?
Answer. The reducing sugars have free aldehydic or ketonic groups.

Question. Give one example each for fibrous protein and globular protein.
Answer. Globular protein – Insulin
Fibrous protein – Keratin

Question. Name two components of starch.
Answer. Amylose and amylopectin are the two components of starch.

Question. Mention the structural feature characterising reducing sugar.
Answer. Reducing sugar : The sugars which reduce Fehling’s solution and Tollen’s reagent are called reducing sugars. For example, all monosaccharides

Short Answer Questions

Question. After watching a programme on TV about the adverse effects of junk food and so drinks on the health of school children, Sonali, a student of Class XII, discussed the issue with the school principal. Principal immediately instructed the canteen contractor to replace the fast food with the bre and vitamins rich food like sprouts, salad, fruits etc. This decision was welcomed by the parents and the students.
After reading the above passage, answer the following questions :
(a) What values are expressed by Sonali and the Principal of the school?
(b) Give two examples of water-soluble vitamins.
Answer. (a) Awareness and social thinking
(b) Vitamin B complex and vitamin C.

Question. Write the structural and functional difference between DNA and RNA.
Answer. Structural differences between DNA and RNA
(i) The sugar in DNA is deoxyribose while that in RNA is ribose.
(ii) DNA has a double-stranded helical structure, while RNA has a single-stranded helical structure.
Functional differences between DNA and RNA
(i) DNA is the chemical basis of heredity and is responsible for maintaining the identity of different species.
(ii) RNA molecules are responsible for protein synthesis but the message for the synthesis of a particular protein is present in DNA

Question. Name the bases present in RNA. Which one of these is not present in DNA?
Answer. The bases present in RNA are adenine (A),
guanine (G) cytosine (C) and

Question. What are essential and non-essential amino acids? Give one example of each type.
Answer. Amino acids which cannot be synthesised in the body and must be obtained through diet are known as essential amino acids, e.g., valine and leucine. There are ten essential amino acids. Amino acids which can be synthesised in the body are known as non-essential amino acids, e.g., alanine and glutamic acids.