Chapter 14 Biomolecules

Question 1. Glycogen is a branched chain polymer of $\alpha$-D-glucose units in which chain is formed by C1—C4 glycosidic linkage whereas branching occurs by the formation of C1-C6 glycosidic linkage. Structure of glycogen is similar to __________.

(i) Amylose

(ii) Amylopectin

(iii) Cellulose

(iv) Glucose

Question 2. Which of the following polymer is stored in the liver of animals?

(i) Amylose

(ii) Cellulose

(iii) Amylopectin

(iv) Glycogen

Question 3. Sucrose (cane sugar) is a disaccharide. One molecule of sucrose on hydrolysis gives _________.

(i) 2 molecules of glucose

(ii) 2 molecules of glucose + 1 molecule of fructose

(iii) 1 molecule of glucose + 1 molecule of fructose

(iv) 2 molecules of fructose

Question 4. Which of the following pairs represents anomers?

(i)

(ii)

(iii)

(iv)

Question 5. Proteins are found to have two different types of secondary structures viz. $\alpha$-helix and $\beta$-pleated sheet structure. $\alpha$-helix structure of protein is stabilised by :

(i) Peptide bonds

(ii) van der Waals forces

(iii) Hydrogen bonds

(iv) Dipole-dipole interactions

Question 6. In disaccharides, if the reducing groups of monosaccharides i.e. aldehydic or ketonic groups are bonded, these are non-reducing sugars. Which of the following disaccharide is a non-reducing sugar?

(i)

(ii)

(iii)

(iv)

Question 7. Which of the following acids is a vitamin?

(i) Aspartic acid

(ii) Ascorbic acid

(iii) Adipic acid

(iv) Saccharic acid

Question 8. Dinucleotide is obtained by joining two nucleotides together by phosphodiester linkage. Between which carbon atoms of pentose sugars of nucleotides are these linkages present?

(i) 5' and 3'

(ii) 1' and 5'

(iii) 5' and 5'

(iv) 3' and 3'

Question 9. Nucleic acids are the polymers of ______________.

(i) Nucleosides

(ii) Nucleotides

(iii) Bases

(iv) Sugars

Question 10. Which of the following statements is not true about glucose?

(i) It is an aldohexose.

(ii) On heating with HI it forms n-hexane.

(iii) It is present in furanose form.

(iv) It does not give 2,4-DNP test.

Question 11. Each polypeptide in a protein has aminoacids linked with each other in a specific sequence. This sequence of amino acids is said to be ____________.

(i) primary structure of proteins.

(ii) secondary structure of proteins.

(iii) tertiary structure of proteins.

(iv) quaternary structure of proteins.

Question 12. DNA and RNA contain four bases each. Which of the following bases is not present in RNA?

(i) Adenine

(ii) Uracil

(iii) Thymine

(iv) Cytosine

Question 13. Which of the following B group vitamins can be stored in our body?

(i) Vitamin $B_1$

(ii) Vitamin $B_2$

(iii) Vitamin $B_6$

(iv) Vitamin $B_{12}$

Question 14. Which of the following bases is not present in DNA?

(i) Adenine

(ii) Thymine

(iii) Cytosine

(iv) Uracil

Question 15. Three cyclic structures of monosaccharides are given below which of these are anomers.

(I)

(II)

(III)

(i) I and II

(ii) II and III

(iii) I and III

(iv) III is anomer of I and II

Question 16. Which of the following reactions of glucose can be explained only by its cyclic structure?

(i) Glucose forms pentaacetate.

(ii) Glucose reacts with hydroxylamine to form an oxime.

(iii) Pentaacetate of glucose does not react with hydroxylamine.

(iv) Glucose is oxidised by nitric acid to gluconic acid.

Question 17. Optical rotations of some compounds along with their structures are given below which of them have D configuration.

(I)

(II)

(III)

(i) I, II, III

(ii) II, III

(iii) I, II

(iv) III

Question 18. Structure of a disaccharide formed by glucose and fructose is given below. Identify anomeric carbon atoms in monosaccharide units.

(i) ‘a’ carbon of glucose and ‘a’ carbon of fructose.

(ii) ‘a’ carbon of glucose and ‘e’ carbon of fructose.

(iii) ‘a’ carbon of glucose and ‘b’ carbon of fructose.

(iv) ‘f ’ carbon of glucose and ‘f ’ carbon of fructose.

Question 19. Three structures are given below in which two glucose units are linked. Which of these linkages between glucose units are between C1 and C4 and which linkages are between C1 and C6?

(i) (A) is between C1 and C4, (B) and (C) are between C1 and C6

(ii) (A) and (B) are between C1 and C4, (C) is between C1 and C6

(iii) (A) and (C) are between C1 and C4, (B) is between C1 and C6

(iv) (A) and (C) are between C1 and C6, (B) is between C1 and C4

Question 20. Carbohydrates are classified on the basis of their behaviour on hydrolysis and also as reducing or non-reducing sugar. Sucrose is a __________.

(i) monosaccharide

(ii) disaccharide

(iii) reducing sugar

(iv) non-reducing sugar

Question 21. Proteins can be classified into two types on the basis of their molecular shape i.e., fibrous proteins and globular proteins. Examples of globular proteins are :

(i) Insulin

(ii) Keratin

(iii) Albumin

(iv) Myosin

Question 22. Which of the following carbohydrates are branched polymer of glucose?

(i) Amylose

(ii) Amylopectin

(iii) Cellulose

(iv) Glycogen

Question 23. Amino acids are classified as acidic, basic or neutral depending upon the relative number of amino and carboxyl groups in their molecule. Which of the following are acidic?

(i)

(ii)

(iii) $H_2N—CH_2—CH_2—CH_2—COOH$

(iv)

Question 24. Lysine, is _______________.

(i) $\alpha$-Amino acid

(ii) Basic amino acid

(iii) Amino acid synthesised in body

(iv) $\beta$-Amino acid

Question 25. Which of the following monosaccharides are present as five membered cyclic structure (furanose structure)?

(i) Ribose

(ii) Glucose

(iii) Fructose

(iv) Galactose

Question 26. In fibrous proteins, polypeptide chains are held together by __________.

(i) van der Waals forces

(ii) disulphide linkage

(iii) electrostatic forces of attraction

(iv) hydrogen bonds

Question 27. Which of the following are purine bases?

(i) Guanine

(ii) Adenine

(iii) Thymine

(iv) Uracil

Question 28. Which of the following terms are correct about enzyme?

(i) Proteins

(ii) Dinucleotides

(iii) Nucleic acids

(iv) Biocatalysts

Question 29. Name the sugar present in milk. How many monosaccharide units are present in it? What are such oligosaccharides called?

Question 30. How do you explain the presence of all the six carbon atoms in glucose in a straight chain?

Question 31. In nucleoside a base is attached at 1' position of sugar moiety. Nucleotide is formed by linking of phosphoric acid unit to the sugar unit of nucleoside. At which position of sugar unit is the phosphoric acid linked in a nucleoside to give a nucleotide?

Question 32. Name the linkage connecting monosaccharide units in polysaccharides.

Question 33. Under what conditions glucose is converted to gluconic and saccharic acid?

Question 34. Monosaccharides contain carbonyl group hence are classified, as aldose or ketose. The number of carbon atoms present in the monosaccharide molecule are also considered for classification. In which class of monosaccharide will you place fructose?

Question 35. The letters ‘D’ or ‘L’ before the name of a stereoisomer of a compound indicate the correlation of configuration of that particular stereoisomer. This refers to their relation with one of the isomers of glyceraldehyde. Predict whether the following compound has ‘D’ or ‘L’ configuration.

Question 36. Aldopentoses named as ribose and 2-deoxyribose are found in nucleic acids. What is their relative configuration?

Question 37. Which sugar is called invert sugar? Why is it called so?

Question 38. Amino acids can be classified as $\alpha$-, $\beta$-, $\gamma$-, $\delta$- and so on depending upon the relative position of amino group with respect to carboxyl group. Which type of amino acids form polypetide chain in proteins?

Question 39. $\alpha$-Helix is a secondary structure of proteins formed by twisting of polypeptide chain into right handed screw like structures. Which type of interactions are responsible for making the $\alpha$-helix structure stable?

Question 40. Some enzymes are named after the reaction, where they are used. What name is given to the class of enzymes which catalyse the oxidation of one substrate with simultaneous reduction of another substrate.

Question 41. During curdling of milk, what happens to sugar present in it?

Question 42. How do you explain the presence of five —OH groups in glucose molecule?

Question 43. Why does compound (A) given below not form an oxime?

(A)

Question 44. Why must vitamin C be supplied regularly in diet?

Question 45. Sucrose is dextrorotatory but the mixture obtained after hydrolysis is laevorotatory. Explain.

Question 46. Amino acids behave like salts rather than simple amines or carboxylic acids. Explain.

Question 47. Structures of glycine and alanine are given below. Show the peptide linkage in glycylalanine.

Question 48. Protein found in a biological system with a unique three-dimensional structure and biological activity is called a native protein. When a protein in its native form, is subjected to a physical change like change in temperature or a chemical change like, change in pH, denaturation of protein takes place. Explain the cause.

Question 49. Activation energy for the acid catalysed hydrolysis of sucrose is 6.22 kJ $mol^{–1}$, while the activation energy is only 2.15 kJ $mol^{–1}$ when hydrolysis is catalysed by the enzyme sucrase. Explain.

Question 50. How do you explain the presence of an aldehydic group in a glucose molecule?

Question 51. Which moieties of nucleosides are involved in the formation of phosphodiester linkages present in dinucleotides? What does the word diester in the name of linkage indicate? Which acid is involved in the formation of this linkage?

Question 52. What are glycosidic linkages? In which type of biomolecules are they present?

Question 53. Which monosaccharide units are present in starch, cellulose and glucose and which linkages link these units?

Question 54. How do enzymes help a substrate to be attacked by the reagent effectively?

Question 55. Describe the term D- and L- configuration used for amino acids with examples.

Question 56. How will you distinguish 1° and 2° hydroxyl groups present in glucose? Explain with reactions.

Question 57. Coagulation of egg white on boiling is an example of denaturation of protein. Explain it in terms of structural changes.

Question 58. Match the vitamins given in Column I with the deficiency disease they cause given in Column II.

Question 59. Match the following enzyms given in Column I with the reactions they catalyse given in Column II.

Question 60. Assertion : D (+) – Glucose is dextrorotatory in nature.

Reason : ‘D’ represents its dextrorotatory nature.

Question 61. Assertion : Vitamin D can be stored in our body.

Reason : Vitamin D is fat soluble vitamin.

Question 62. Assertion : $\beta$-glycosidic linkage is present in maltose,

Reason : Maltose is composed of two glucose units in which C–1 of one glucose unit is linked to C–4 of another glucose unit.

Question 63. Assertion : All naturally occurring $\alpha$-aminoacids except glycine are optically active.

Reason : Most naturally occurring amino acids have L-configuration.

Question 64. Assertion : Deoxyribose, $C_5H_{10}O_4$ is not a carbohydrate.

Reason : Carbohydrates are hydrates of carbon so compounds which follow $C_x(H_2O)_y$ formula are carbohydrates.

Question 65. Assertion : Glycine must be taken through diet.

Reason : It is an essential amino acid.

Question 66. Assertion : In presence of enzyme, substrate molecule can be attacked by the reagent effectively.

Reason : Active sites of enzymes hold the substrate molecule in a suitable position.

Question 67. Write the reactions of D-glucose which can’t be explained by its open-chain structure. How can cyclic structure of glucose explain these reactions?

Question 68. On the basis of which evidences D-glucose was assigned the following structure?

Question 69. Carbohydrates are essential for life in both plants and animals. Name the carbohydrates that are used as storage molecules in plants and animals, also name the carbohydrate which is present in wood or in the fibre of cotton cloth.

Question 70. Explain the terms primary and secondary structure of proteins. What is the difference between $\alpha$-helix and $\beta$-pleated sheet structure of proteins?

Question 71. Write the structures of fragments produced on complete hydrolysis of DNA. How are they linked in DNA molecule? Draw a diagram to show pairing of nucleotide bases in double helix of DNA.