Q. Classify the following into monosaccharides and disaccharides.
Ribose, 2-deoxyribose, maltose, galactose, fructose and lactose.
Ans. Ribose, 2-deoxyribose, galactose, fructose – monosaccharides, Maltose and lactose - disaccharides.
Q. Where does the water present in the egg go after boiling the egg?
Ans. When an egg is boiled in water, the water present in egg is used in denaturation of protein probably
through H-bonding.
Q Why cannot vitamin C be stored in our body?
Ans. Because it is soluble in water and readily excreted in urine and cannot be stored in our body.
Q. Enumerate the reactions of D-glucose which cannot be explained by its open chain structure.
Ans. (i) Despite having aldehyde group, glucose does not give Schiff test and 2.,4-DNP test.
(ii)Glucose does not react with sodium hydrogen bisulphite to form addition product.
(ii)The pentaacetate of glucose does not react with hydroxyl amine showing the absence of free -CHO
group.
Q. What are essential and non-essential amino acids? Give two examples of each type
.
Ans. The amino acids which can be made by our bodies and are not required in our diet are called non-essential amino acids. For example, glycine and alanine. The amino acids which cannot be made by our bodies and must be supplied in our diet are called essential amino acids. For example, valine and leucine.
Q. What happens when D-glucose is treated with the following reagents? (i) HI (i) Bromine water (iii) HNO3
Ans. (i) when glucose is treated with HI, it forms n-hexane.
(i) when glucose is treated with Bromine water, gluconic acid is formed.
(iii) when glucose is treated with nitric acid, Saccharic acid is formed.
Q. Define the following as related to proteins
(i)Peptide linkage (i) Primary structure (ii) Denaturation
.
Ans. (i)Peptide linkage- Peptide bond is formed by the condensation of two or more, same or different
∝-amino acids. -CO0-NH- Iinkage is called peptide inkage.
(ii) Primary structure- Primary structure of proteins give the sequence in which amino acids are linked
in one or more polypeptide chains of proteins.
(iii) Denaturation- A process that changes the physical and biological properties without affecting the chemical composition of a protein is called denaturation. The denaturation is caused by certain physical or chemical treatments such as in pH, temperature, presence of some salts or certain chemical agents.
Q. (a) How do you explain the amphoteric behaviour of amino acids?
(b)The melting points and solubility in water of amino acids are generally higher than that of the corresponding halo acids. Explain.
Ans. (a) Due to dipolar or Zwitter ion structure, amino acids are amphoteric in nature. The acidic character of the amino acids due to the -NH3 group and the basic character is due to the -CO0- group.
(b)Amino acids have strong electrostatic attraction and hence have high melting points and highly soluble in water.
Q. Differentiate the following
(i) Globular and fibrous proteins.
(ii) Nucleoside and a nucleotide.
Ans. (i) Fibrous proteins: They are long and thread like and tend to lie side by side to form fibers. In some cases, they are held together by hydrogen bonds at many points. These proteins serve as a chief structural material of animal tissues. Examples, keratin, collagen
Globular proteins: The molecules of these proteins are folded into compact units and form spheroid shapes. Intermolecular forces are weak. These proteins are soluble in water or aqueous solution of acids, bases or salts. Globular proteins make up all enzymes, hormones, fibrinogen etc. Examples, hemoglobin, insulin
(ii) The nitrogenous base and a pentose sugar are called as nucleosides. The nitrogenous base, a pentose sugar and a phosphate group are called as nucleotides.
Q15. (a) Name the vitamins in each case whose deficiency causes
(1) Night blindness
(ii) Rickets
(iii) Poor coagulation of blood
(iv) Scurvy
(b)What is isoelectric point?
(c)Which amino acid is not optically active?
Ans. (a) (i)) Vitamin A (ii) Vitamin D (ii) Vitamin K (iv) Vitamin C
(b)The pH at which no net migration of amino acid takes place under the influence of an applied electric field is called isoelectric point. For example, isoelectric point of glycine is 6.1.
(c)Glycine, NH2CH2COOH
Main point of differences between DNA and RNA:
DNA (Deoxyribonucleic acid) RNA (Ribonucleic acid)
| DNA (Deoxyribonucleic acid) |
RNA (Ribonucleic acid) |
| 1.It occurs mainly in the nucleus of the cell. |
1.It occurs in the cytoplasm of the cell. |
| 2.It has double stranded α-helix structure in which two strands are coiled spirally in opposite directions. |
2.It has single stranded α-helix structure |
| 3.The sugar molecule is 2-deoxyribose. |
3.The sugar molecule is ribose. |
| 4.Nitrogenous base uracil is not present. |
4.Nitrogenous base thymine is not present. |
| 5.DNA has unique property of replication. |
5.RNA usually does not replicate. |
| 6.It is responsible for the transmission for heredity character. |
6.Helps in protein biosynthesis |
| 7.DNA molecules are very large; their molecular masses may vary from 6 x 106 – 16 x 106 u. |
7.RNA molecules are much smaller with molecular mass ranging from 2 x 104 – 4x104 u. |