XII Chemistry-Biomolecules Past Papers PDF

Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® Previous HSE Questions and Answers from the chapter “BIOMOLECULES” 1. Glucose is commercially prepared from a polysaccharide. a) Which is the polysaccharide used for the production of glucos...

Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® Previous HSE Questions and Answers from the chapter “BIOMOLECULES” 1. Glucose is commercially prepared from a polysaccharide. a) Which is the polysaccharide used for the production of glucose? (1) b) Name the process involved in the formation of glucose in the above method? (1) [March 2008] Ans: a) Starch b) Hydrolysis 2. Sucrose is fermented by yeast to ethyl alcohol. What are the enzymes used in this conversion? (2) [SAY 2008] Ans: Invertase and zymase 3. Carbohydrates are classified into three classes - monosaccharides, oligosaccharides and polysaccharides. a) What are polysaccharides? (1) b) Give two examples of polysaccharides? (1) c) What is invert sugar? (1) d) What is the basic structural difference between Starch and Cellulose? (1) [March 2010] Ans: a) Polysaccharides are carbohydrates which give a large number of monosaccharide units on hydrolysis. b) Starch and Cellulose c) The product obtained after the hydrolysis of cane sugar (sucrose) is called invert sugar. It is a mixture of D-(+)-glucose and D-(-)-fructose. d) Starch is a polymer of α-D-glucose, while Cellulose is a polymer of β-D-glucose. 4. a) Names of carbohydrates, their properties and structural patterns are given below. Match them properly. (2) Glucose Disaccharide d-1,4 link Sucrose Reducing Galactoxide Lactose Insoluble (in water) 1,6-linkage Amylopectin Non-reducing Fructoxide Trisaccharide Anomers present Monosaccharide 2-glucose units linked b) Proteins have polypeptide bonds. What are polypeptides? (1) [March 2011] Ans: a) Glucose Monosaccharide Anomers present Or, Reducing Sucrose Disaccharide Fructoxide Or, Non-reducing Lactose Reducing Galactoxide Or, Disaccharide Amylopectin Insoluble (in water) 1,6-linkage b) If the number of amino acid molecules in a peptide is more than 10, it is called a polypeptide. 5. Proteins are the polymers of α-aminoacids. The structure and shape of proteins can be discussed at four levels, namely primary, secondary, tertiary and quaternary. Give an account of the structure and shape of proteins considering the above four levels. (3) [SAY 2011] Biomolecules – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 1  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® Ans: There are four types of structure for a protein. They are primary, secondary, tertiary and quaternary structure. 1. Primary structure: It gives the sequence of amino acid molecules in a polypeptide chain of protein. 2. Secondary structure: It gives the different shapes in which polypeptide chain can exist. There are two different types of secondary structures - α-helix and β-pleated sheet structure. 3.Tertiary structure: It refers to the further folding of the secondary structure. It gives rise to two major molecular shapes - fibrous and globular. 4. Quaternary structure: Some of the proteins contain two or more polypeptide chains called sub- units. The spatial arrangement of these sub-units is known as quaternary structure. 6. a) Carbohydrates are classified into monosaccharides, oligosaccharides and polysaccharides. i) What is the basis of such classification? (1½) ii) Give an example for an oligosaccharide. (½) b) Vitamin ‘C’ is a vitamin found in fruits and vegetables. It cannot be stored in our body. Why? (1) [March 12] Ans: a) (i) It is based on the behaviour on hydrolysis. (ii) Sucrose or, maltose or, lactose. b) Since vitamin C is water soluble, it cannot be stored in our body. 7. Proteins are important polymers of biological systems. i) What is denaturation of proteins? (1) ii) Give two examples of denaturation. (1) [SAY 2012 & March 2009] Ans: i) When a protein is subjected to physical change (like change in temperature) or chemical change (like change in pH), it loses the biological activities. This process is called denaturation of protein. ii) Coagulation egg white on boiling and curdling of milk. 8. a) Amino acids can be classified into essential amino acids and non essential amino acids. i) What is the basis of such classification? (1) ii) Write one example each for essential and non essential amino acids. (1) b) Write any two differences between DNA and RNA. (1) [March 2013] Ans: a) i) Based on the way by which an aminoacid is obtained in our body. ii) E.g. for essential aminoacid is Lysine and for non-essential aminoacid is Glycine. b) DNA RNA The pentose sugar in DNA is 2-deoxy ribose The pentose sugar in RNA is ribose The nitrogen bases present in DNA are In RNA, instead of Thymine, Uracil is Adenine, Guanine, Cytosine and Thymine. present. DNA is double stranded RNA is single stranded [Any 2 differences required] 9. Name the products obtained in the following reactions. a) C6H12O6 Bromine water ………….. (½) b) C6H12O6 HI/heat …………… (½) c) What is invert sugar? (1) d) Name two polysaccharides. (1) [SAY 2013] Ans: a) Gluconic acid b) n-Hexane c) The product obtained after the hydrolysis of cane sugar (sucrose) is called invert sugar. d) Starch and cellulose. Biomolecules – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 2  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® 10. Biomolecules are formed by certain specific linkages between simple monomeric units. Write the names of linkages and monomeric units in the following class of biomolecules. i) Starch ii) Protein iii) Nucleic acid (3) [March 2014] Ans: i) Starch - Glycosidic linkage – α-D-glucose ii) Protein - Peptide linkage – amino acid iii) Nucleic acid – Phosphodiester linkage (H Bonds) - nucleotide 11. a) Name a fat soluble vitamin. Suggest a disease caused by its deficiency. (1) b) What do you mean by the following: i) Secondary structure of proteins. ii) Nucleosides. (1 x 2 = 2) [SAY 2014] Ans: a) Vitamin D. Deficiency disease is Rickets. [Vitamin A, D, E & K are fat soluble] b) i) Secondary structure gives the different shapes in which polypeptide chain can exist in a protein. There are two different types of secondary structures - α-helix and β-pleated sheet structure. ii) In nucleic acids, the pentose sugar combines with the nitrogen base to form nucleosides. 12. Carbohydrates are broadly divided into monosaccharides, oligosaccharides and polysaccharides. a) Write one example each of monosaccharide and oligosaccharide. (1) b) i) Write any one method of preparation of glucose. (1) ii) What is a peptide linkage? (1) [March 2015] Ans: a) Glucose is a monosaccharide and sucrose is an oligosaccharide. b) i) Fermentation of cane sugar ii) –CO-NH- linkage in protein is called peptide bond. 13. a) Match the following structures of proteins in column I with their characteristic features in column II Column I Column II i) Primary structure a) Spatial arrangement of polypeptide sub units ii) Secondary structure b) Structure of amino acids iii) Tertiary structure c) Folding of peptide chains iv) Quaternary structure d) Sequence of amino acids e) Fibrous or globular nature (2) b) What is denaturation of proteins? (1) [SAY 2015] Ans: a) Column I Column II i) Primary structure d) Sequence of amino acids ii) Secondary structure c) Folding of peptide chains iii) Tertiary structure e) Fibrous or globular nature iv) Quaternary structure a) Spatial arrangement of polypeptide sub units b) Refer the Answer of the Question number 7 (i) 14. Cane Sugar, Glucose and Starch are Carbohydrates. a) Represent the structure of Glucose. (1) Biomolecules – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 3  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® b) Write a method to prepare Glucose from Starch. Write the chemical equation of the reaction. (1) c) Suggest any two uses of Carbohydrates. (1) [March 2016] Ans: a) α-D-(+)-Glucose α-D-(+)-Glucopyranose b) Glucose is obtained by hydrolysis of starch by boiling it with dilute H2SO4 at 393 K under pressure. (C6H10O5)n + nH2O ⎯⎯⎯⎯⎯⎯⎯→ nC6H12O6 c) Carbohydrates are used as raw materials for many important industries like textiles, paper, lacquers and breweries. Carbohydrate in the form of wood is used for making furniture etc. 15. Proteins are Biomolecules. a) What is denaturation of protein? (1) b) Match the following: Vitamin A Glucose Starch Zymase Aldohexose Night blindness Enzyme Amylose Fructose (2) [SAY 2016] Ans: a) Refer the Answer of the Question number 7 (i) b) Vitamin A Night blindness Starch Amylose Aldohexose Glucose Enzyme Zymase 16. a) Which of the following is a polysaccharide? i) Maltose ii) sucrose iii) fructose iv) cellulose (1) b) Explain the amphoteric behaviour of aminoacid. (2) [March 2017] Ans: a) Cellulose b) Amino acids contain both acidic (carboxyl group) and basic (amino group) groups. In aqueous solution, they form internal salts known as zwitter ions. In zwitter ionic form, amino acids show amphoteric behaviour. 17. a) α-D-(+) glucose and β-D-(+) glucose are: i) Metamers ii) Anomers iii) Geometrical isomers iv) Functional group isomers (1) b) What is denaturation of proteins? (1) c) Differentiate between nucleoside and nucleotide. (1) [SAY 2017] Ans: a) Anomers Biomolecules – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 4  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® c) Refer the Answer of the Question number 7 (i) d) Nucleoside is formed by the combination of pentose sugar with nitrogen base. Nucleoside combines with phosphoric acid unit to form nucleotide. 18. Which among the given vitamins is water soluble? a) A b) B c) D d) E (1) Ans: B 19. State two differences between globular and fibrous proteins. (2) [March 2018] Ans: Fibrous protein Globular protein It has fibre-like shape It has spherical shape It is water insoluble It is water soluble Here the polypeptide chains Here the chains of run parallel and are held polypeptides coil around together by hydrogen and to give a spherical shape. disulphide bonds. E.g.: Keratin and myosin E.g. Insulin and albumins. [Any 2 differences required] 20. Which vitamin is responsible for blood clotting? (1) Ans: Vitamin K 21. Describe primary and secondary structure of proteins. (2) [SAY 2018] Ans: Refer the Answer of the Question number 5. 22. Give the open chain and ring structures of glucose and account for the existence of glucose in two anomeric forms. (3) [March 2019] Ans: Open chain structure Ring Structures The existence of glucose in two anomeric forms can be explained by the formation of 1,5-ring structure. Now the first carbon also becomes asymmetric and hence glucose exists in two anomeric forms. The structure in which -OH group of 1st carbon on the same side of the ring is called α–form and that on the opposite side of the ring is called β–form. 23. Write any three differences of RNA and DNA. (3) [SAY 2019] Ans: Refer the Answer of the Question number 8 (b) 24. (a) Differentiate between globular and fibrous proteins. (2) (b) The deficiency of which vitamin causes night-blindness. (1) [March 2020] Ans: (a) Refer the Answer of the Question number 19. Biomolecules – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 5  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® (b) Vitamin A 25. Glucose is commercially prepared from polysaccharide. (a) Which is the polysaccharide used for the production of glucose? (1) (b) Give two examples for disaccharides. (1) (c) What is invert sugar? (1) [SAY 2020] Ans: (a) Starch (b) Sucrose and Lactose (c) The product obtained after the hydrolysis of cane sugar (sucrose) is called invert sugar. It is a mixture of D-(+)-glucose and D-(-)-fructose. 26. (i) Classify the following into monosaccharides and disaccharides: Ribose, Fructose, Maltose, Sucrose. (1) (ii) How is starch different from glycogen? (1) (iii) Name the two hormones which work together to regulate glucose level in the body. (1) [March 2021] Ans: (i) Monosaccharides: Ribose, Fructose Disaccharides: Maltose, Sucrose. (ii) Starch is the storage polysaccharide of plants while glycogen is the storage polysaccharide of animals. (iii) Insulin and glucagon. 27. (i) Explain the classification of proteins based on their molecular shape. (2) (ii) What is meant by denaturation of protein? (1) [SAY 2021] Ans: (i) Based on molecular structure, proteins are classified into two – fibrous and globular proteins. Fibrous proteins have fibre – like structure. Here the linear polypeptide chains are held together by H-bond and disulphide bond. They are generally insoluble in water. E.g. Keratin and myosin. In Globular proteins the chains of polypeptides coil around to give a spherical shape. These are usually soluble in water. E.g.: Insulin and albumins. (ii) Refer the Answer of the Question number 7 (i) 28. Identify the peptide bond among the following : (1) Ans: -CO-NH- 29. (i) What are oligosaccharides? Give an example. (2) (ii) What is glycogen? (1) (iii) Explain the chemical constitution of starch. (1) [March 2022] Ans: (i) Oligosaccharides are carbohydrates which give two to ten monosaccharide units on hydrolysis. E.g. Sucrose, maltose, lactose. (ii) Glycogen is the storage polysaccharide of animals. It is also known as animal starch. (iii) Starch is a polymer of α-glucose and consists of two components - Amylose and Amylopectin. 30. The carbohydrate stored in liver, muscles and brain of animals is ______. (1) Biomolecules – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 6  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® Ans: Glycogen 31. (i) What is the glycosidic linkage in carbohydrates? (2) (ii) How can you prepare glucose from sucrose? Why sucrose is a non-reducing sugar? (2) [SAY 2022] Ans: (i) C-O-C linkage present in oligosaccharides and polysaccharides is called glycosidic linkage. Or, in a disaccharide or polysaccharide, the monosaccharides are joined together through oxide linkage by losing water molecules. Such a linkage (C-O-C) between monosaccharide units through oxygen atom is called glycosidic linkage. (ii) Glucose is prepared by the hydrolysis of sucrose in presence of dil. mineral acids. C12H22O11 + H2O ⎯⎯⎯→ C6H12O6 + C6H12O6 In Sucrose, the reducing groups of glucose and fructose (aldehydic and ketonic groups) are involved in glycosidic bond formation. So it is non-reducing. 32. What are oligosaccharides ? Give any two examples. (2) Ans: Refer the answer of the Question number 29 (i) 33. (i) What are essential and non-essential amino acids ? (1) (ii) Explain the amphoteric behaviour of amino acids. (2) [March 2023] Ans: (i) Aminoacids which are not synthesized in our body and should be obtained through diet are called essential aminoacids. E.g. Lysine Aminoacids which are synthesized in our body are called non-essential aminoacids. E.g. Glycine (ii) Refer the answer of the Question number 16 (b). 34. What do you mean by denaturation of proteins ? (2) Refer the answer of the Question number 7 (i) 35. (i) What are polysaccharides ? Give two examples. (2) (ii) Name the products of Hydrolysis of sucrose. (1) [SAY 2023] Ans: (i) Refer the answer of the Question number 3 (a) (ii) Glucose and fructose. 36. Name the linkage between two monosaccharide units in a disaccharide. (1) Ans: Glycosidic linkage or C – O – C linkage 37. Write the classification of proteins on the basis of their molecular shape by giving suitable examples. (3) [March 2024] Ans: Refer the answer of the Question number 27 (i) 38. The non-essential amino acid in the following is _________. (a) glycine (b) valine (c) leucine (d) lysine (1) Ans: glycine 39. (i) What are enzymes ? (1) (ii) Name the disease caused by deficiency of vitamin A. (1) (iii) Explain the denaturation of protein. (1) [SAY 2024] Ans: (i) Enzymes are biological catalysts, which catalyse the different reactions taking place in living body. (ii) Night blindness OR, Xerophthalmia (iii) Refer the answer of the Question number 7. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Biomolecules – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 7