Biomolecules Class 12 Chemistry Important Questions

Students can read the important questions given below for Biomolecules Class 12 Chemistry. All Biomolecules Class 12 Notes and questions with solutions have been prepared based on the latest syllabus and examination guidelines issued by CBSE, NCERT and KVS. You should read all notes provided by us and Class 12 Chemistry Important Questions provid ed for all chapters to get better marks in examinations. Chemistry Question Bank Class 12 is available on our website for free download in PDF.

Important Questions of Biomolecules Class 12

Very Short Answer Questions

Question. Write the product obtained when D-glucose reacts with H₂N—OH. 
Answer. D-Glucose reacts with H₂N—OH to give glucose oxime.

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. Write the structure of the product obtained when glucose is oxidised with nitric acid.
Answer. On oxidation with nitric acid, D – glucose yields saccharic acid.

Question. Write a reaction which shows that all the carbon atoms in glucose are linked in a straight chain.
Answer. Glucose when heated with red P and HI gives n-hexane.

It indicates presence of straight chain of six carbon atoms in glucose.

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

Question. Write the product formed on reaction of D-glucose with Br² water.
Answer. D – Glucose gets oxidised to six carbon carboxylic acid (gluconic acid) on reaction with bromine water.

Question. Write the product formed when glucose is treated with HI.
Answer. On prolonged heating with HI, D-Glucose forms n-hexane.

Short Answer Questions

Question. Aer 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.
Aer 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. What is a glycosidic linkage?
Answer. The two monosaccharides are joined together by an oxide linkage formed by the loss of water molecule. Such linkage is called glycosidic linkage

Question. What is the difference between fibrous protein and globular protein?
Answer. Characteristic differences between globular and fibrous proteins can be given as :

Question. Answer the following question briefly :
How are carbohydrates classified?
Answer. On the basis of hydrolysis, carbohydrates can be divided in three major classes :
(i) Monosaccharides : These cannot be hydrolysed into simpler molecules. These are further classied as aldoses and ketoses.
(ii) Oligosaccharides : These are the carbohydrates which on hydrolysis give 2 – 10 monosaccharides.
For example, sucrose, lactose, maltose, etc.
(iii) Polysaccharides : These are high molecular mass carbohydrates which give many molecules of monosaccharides on hydrolysis. For example starch and cellulose.

Question. How are the vitamins classified? Mention the chief sources of vitamins A and C.
Answer. Vitamins are classied into two groups depending upon their solubility in water or fat.
(i) Fat soluble vitamins.
(ii) Water soluble vitamins.
Sources of vitamin A : Fish, liver oil, carrots, butter and milk.
Sources of vitamin C : Citrus fruits, amla and green leafy vegetables.

Question. B-complex is an oen prescribed vitamin. What is complex about it and what is its usefulness?
Answer. B-complex is a group of vitamins which contains vitamins B₁, B₂, B₆, B₁₂, biotin, folic acid, pantothenic acid and nicotinic acid. It is required to release energy from food and to promote healthy skin and muscles. Its deciency causes beri beri and pernicious anaemia.

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.

Long Answer Questions

Question. What is essentially the difference between a-form and b-form of glucose? Explain.
Answer. In a-D Glucose, the –OH group at C₁ is towards right whereas in b-glucose, the –OH group at C₁ is towards le. Such a pair of stereoisomers which differ in the configuration only at C₁ are called anomers.

Question. Define the following term :
Anomers 
Answer. The pair of stereoisomers which differ only in the configuration of the hydroxyl group at C₁ are called anomers.