Question 1

Q1: What are monosaccharides?

Accepted Answer

Monosaccharides are carbohydrates that cannot be hydrolysed further to give simpler units of polyhydroxy aldehydes or ketones. They are the simplest form of carbohydrates. About 20 monosaccharides are known to occur in nature. Some common examples include glucose, fructose, and ribose.

Question 2

Q10: Enumerate the reactions of D-glucose which cannot be explained by its open chain structure.

Accepted Answer

The following reactions and facts about D-glucose cannot be explained by its open-chain structure: 1.  Schiff's Test and $\mathrm{NaHSO}_3$ Addition: Despite having an aldehyde group, glucose does not give a positive Schiff's test and does not form an addition product with sodium hydrogensulphite ($...

Question 3

Q11: What are essential and non-essential amino acids? Give two examples of each type.

Accepted Answer

Essential Amino Acids: These are amino acids that cannot be synthesized by the human body and must be obtained through diet. Their deficiency can lead to diseases.    Examples: Valine, Leucine, Phenylalanine, Tryptophan. Non-essential Amino Acids: These are amino acids that can be synthesized by the...

Question 4

Q12: Define the following as related to proteins (i) Peptide linkage (ii) Primary structure (iii) Denaturation.

Accepted Answer

(i) Peptide linkage: A peptide linkage (or peptide bond) is a covalent chemical bond formed between two amino acid molecules. It is an amide bond formed when the carboxyl group (-COOH) of one amino acid reacts with the amino group (-$\mathrm{NH}_2$) of another amino acid, with the elimination of a m...

Question 5

Q13: What are the common types of secondary structure of proteins?

Accepted Answer

The secondary structure of a protein refers to the shape in which a long polypeptide chain can exist due to regular folding of its backbone. The two most common types of secondary structure are: 1.  $\alpha$-Helix: In this structure, the polypeptide chain twists into a right-handed spiral or helix....

Question 6

Q14: What type of bonding helps in stabilising the $\alpha$-helix structure of proteins?

Accepted Answer

The $\alpha$-helix structure of proteins is stabilized by intramolecular hydrogen bonds. These bonds form between the carbonyl oxygen (>C=O) of one amino acid residue and the amide hydrogen (-NH) of the amino acid residue that is four positions ahead in the polypeptide chain. This regular pattern of...

Question 7

Q15: Differentiate between globular and fibrous proteins.

Accepted Answer

Question 8

Q16: How do you explain the amphoteric behaviour of amino acids?

Accepted Answer

Amino acids exhibit amphoteric behaviour because they contain both an acidic group (the carboxyl group, -COOH) and a basic group (the amino group, -$\mathrm{NH}_2$) in the same molecule. In an aqueous solution, the carboxyl group can donate a proton, and the amino group can accept a proton, leading...

Question 9

Q17: What are enzymes?

Accepted Answer

Enzymes are biological catalysts that increase the rate of chemical reactions within living organisms. Almost all enzymes are globular proteins. They are highly specific in their action, meaning a particular enzyme typically catalyzes only one specific reaction or acts on a specific substrate. They...

Question 10

Q18: What is the effect of denaturation on the structure of proteins?

Accepted Answer

Denaturation has a significant effect on the higher levels of protein structure. When a protein is denatured, its secondary and tertiary structures are disrupted and destroyed. The hydrogen bonds, disulphide linkages, and other forces that maintain the folded, three-dimensional shape of the protein...

Question 11

Q19: How are vitamins classified? Name the vitamin responsible for the coagulation of blood.

Accepted Answer

Vitamins are classified into two groups based on their solubility: 1.  Fat-soluble vitamins: These vitamins are soluble in fats and oils but insoluble in water. They can be stored in the liver and adipose (fat-storing) tissues. The vitamins in this group are A, D, E, and K. 2.  Water-soluble vitamin...

Question 12

Q2: What are reducing sugars?

Accepted Answer

Reducing sugars are carbohydrates that can reduce Fehling's solution and Tollens' reagent. This property is due to the presence of a free aldehyde or ketonic group. All monosaccharides, whether they are aldoses or ketoses, are reducing sugars. Disaccharides like maltose and lactose are also reducing...

Question 13

Q20: Why are vitamin A and vitamin C essential to us? Give their important sources.

Accepted Answer

Vitamin A: -   Essential because: It is crucial for vision, growth, and maintaining healthy epithelial tissues. Its deficiency causes diseases like xerophthalmia (hardening of the cornea of the eye) and night blindness. -   Important Sources: Fish liver oil, carrots, butter, and milk. Vitamin C (Asc...

Question 14

Q21: What are nucleic acids? Mention their two important functions.

Accepted Answer

Nucleic acids are long-chain polymers of nucleotides, also known as polynucleotides. They are biomolecules found in the nucleus of living cells and are responsible for the transmission of inherent characters (heredity). The two main types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucl...

Question 15

Q22: What is the difference between a nucleoside and a nucleotide?

Accepted Answer

The main difference between a nucleoside and a nucleotide is the presence of a phosphate group. -   Nucleoside: A nucleoside is formed when a nitrogenous base (like adenine, guanine, cytosine, thymine, or uracil) is attached to the 1' position of a pentose sugar (either ribose or deoxyribose).     N...

Question 16

Q23: The two strands in DNA are not identical but are complementary. Explain.

Accepted Answer

The statement means that the sequence of bases in one strand of the DNA double helix is not the same as the sequence in the other strand. Instead, the sequence of one strand determines the sequence of the other due to specific base pairing rules. The two strands are held together by hydrogen bonds f...

Question 17

Q24: Write the important structural and functional differences between DNA and RNA.

Accepted Answer

Question 18

Q25: What are the different types of RNA found in the cell?

Accepted Answer

There are three main types of RNA found in the cell, each with a specific function in protein synthesis: 1.  Messenger RNA (mRNA): This type of RNA carries the genetic code from the DNA in the nucleus to the ribosomes in the cytoplasm. It acts as a template for protein synthesis. 2.  Ribosomal RNA (...

Question 19

Q3: Write two main functions of carbohydrates in plants.

Accepted Answer

Two main functions of carbohydrates in plants are: 1.  Structural Material: Cellulose, a polysaccharide, is a major component of the cell wall of plant cells, providing structural rigidity and support. 2.  Food Storage: Starch, another polysaccharide, is the main storage form of energy in plants. It...

Question 20

Q4: Classify the following into monosaccharides and disaccharides. Ribose, 2-deoxyribose, maltose, galactose, fructose and lactose.

Accepted Answer

The classification is as follows: Monosaccharides: - Ribose - 2-deoxyribose - Galactose - Fructose Disaccharides: - Maltose - Lactose

NCERT Solutions