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What are monosaccharides?

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Refer Que. no. 3 Page no. 307

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What are reducing sugars?

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Refer Que. no. 14 Page no. 311

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Write the two main functions of carbohydrates in plants.

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Refer Que. no. 23 Page no. 313

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Classify the following into monosaccharides and disaccharides. Ribose, 2-deoxy ribose; maltose; galactose; fructose and lactose.

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Monosaccharide compounds:
Ribose, 2-deoxyribose, galactose, and fructose.
Disaccharide compounds: Maltose and lactose

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What do you understand by the term glycosidic linkage?

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Refer Que. no. 13 Page no. 310

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What is glycogen? How is it different from starch?

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Refer Que. no. 22 Page no. 313

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What are the hydrolysis products of (i) sucrose and (ii) lactose?

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(i) On hydrolysis sucrose give one molecule of
a–D glucose and b–D fructose.
C12H22O11 + H2O → C6H12O6 + C6H12O6
Sucrose a–D Glucose b–D Fructose
(ii) On hydrolysis lactose gives one molecule of
β-D-galactose and β-D-glucose.
C12H22O11 + H2O → C6H12O6 + C6H12O6
Lactose β–D– β–D–
Galactose Glucose

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What is the basic structural difference between starch and cellulose?

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Refer Que. no. 20 Page no. 313

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What happens when D-glucose is treated with the following reagents? (i) HI (ii) Bromine water (iii) HNO3

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(i) Reactions with HI: When D-glucose is heated with HI for long time, n-Hexane is formed, it shows all 6–carbon atoms are linked in linear chain.
(ii) Reactions with Br2 water: Glucose gets oxidised to six carbon carboxylic acid (gluconic acid) on reaction with mild oxidising agent like Br2 water. This indicates that the carbonyl group is present as an aldehyde group.
(iii) Reactions with HNO3: On oxidation with HNO3 glucose as well as gluconic acid both yield a dicarboxylic acid, saccharic acid. This indicates the presence of a primary alcoholic (–OH) group in glucose.

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Enumerate the reactions of D-glucose which can not be explained by its open chain structure.

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Open chain structure of glucose has free aldehyde (–CHO) group even though following reactions and facts could not be explained by this structure.
(i) Despite having the aldehyde group, glucose does not give Schiff’s test and its does not form the hydrogensulphate addition product with NaHSO3.
(ii) The penta-acetate of glucose does not react with hydroxyl amine indicating the absence of free –CHO group.
(iii) Glucose is found to exist in two different crystalline forms which are named as a and b. The a form of glucose (m.p 419K) is obtained by crystallization from concentrated solution of glucose at 303 K while the b-form (m.p 423K) is obtained by crystallization from hot and saturated aqueous solution at 371 K.

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What are essential and non essential amino acids? Give 2 examples of each type.

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Refer Que. no. 28 Page no. 314

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

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(i) Peptide linkage: The amide formed between –COOH group of one molecule of an amino acid and –NH2 group of another molecule of the amino acid by the elimination of a water molecule is called a peptide linkage.
(ii) Primary structure: The primary structure of protein refers to the specific sequence in which various amino acids are present in it, i.e., the sequence of linkage between amino acids in a polypeptide chain. The sequence in which amino acids are arranged is different in each protein. A change in the sequence creates a different protein.
(iii) Denaturation: In a biological system, a protein is found to have a unique 3-D structure and a unique biological activity. In such a situation, the protein is called native protein.
However, when the native protein is subjected to physical changes such as change in temperature or chemical change such as change in pH, its H-bonds are disturbed.
The disturbance unfolds the globules and uncoils the helix. As a result the protein loss its biological activity.
This loss of biological activity by the protein is called denaturation.
During denaturation, the secondary and the tertiary structures of the protein get destroyed, but the primary structure remains unaltered.
One of the examples of denaturation of proteins is the coagulation of egg white when an egg is boiled.

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What are the common types of secondary structure of proteins?

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Refer Que. no. 32 Page no. 316

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What type of bonding helps in stabilising the a-helix structure of proteins?

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Refer Que. no. 34 Page no. 317

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Differentiate between globular and fibrous proteins.

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Refer Que. no. 37 Page no. 317

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How do you explain the amphoteric behaviour of amino acids?

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Refer Que. no. 26 Page no. 314

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What are enzymes?

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Refer Que. no. 39 Page no. 317

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What is the effect of denaturation of the structure of proteins?

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Refer Que. no. 38 Page no. 317

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

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Refer Que. no. 43 Page no. 318

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

[Topic 10.4] [2 Marks]

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Deficiency of vitamin A leads to xerophthalmia (hardening of cornea of eye) and night blindness so it is essential for us. Important sources are fish liver oil, carrots butter and milk.
Deficiency of vitamin C leads to scurvy (bleeding gums) so it is essential for us - Important sources are citrus fruits, amla and green leafy vegetables.

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What are nucleic acids? Mention their two important function.

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A polymer made up of pentose sugar, Heterocyclic bases and phosphate ion containing nucleotide is known as nucleic acids.
Nucleic acids are responsible for protein synthesis in a cell. It is responsible for the transmission of inherent characters from one generation to the next. This process of transmission is called heredity.

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What is the difference between a nucleoside and a nucleotide?

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Refer Que. no. 50 Page no. 320

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

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In the helical structure of DNA, the two strands are held together by hydrogen bonds between specific pairs of bases. Cytosine forms hydrogen bonds with guanine, while adenine forms hydrogen bonds with thymine. As a result the two strands are complementary to each other.

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

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Structural differences

DNA

RNA

(i) The sugar moiety in DNA molecules is b–D–2–deoxyribose

(i) The sugar moiety in RNA molecules is b–D–ribose.

(ii) DNA contains cytosine
and thymine as a pyrimidine base where
as guanine and adenine
as a purine base.

(ii) RNA contains cytosine and uracil as a pyrimidine base where as guanine and adenine as a purine base.

(iii) The helical structure of DNA is double stranded.

(iii) The helical structure of RNA is single stranded.

(iv) DNA molecule is too
large. It’s molecular
mass is 6 × 106 – 16 × 106 u.

(iv) RNA molecule is quite smaller. It’s molecular mass is 20000–40000 u.

Functional differences

DNA

RNA

(i) DNA molecules are capable of self-replication.

(i) RNA molecules are not capable of self-replication.

(ii) DNA is responsible for the transmission of genetic characters.

(ii) RNA is responsible for the synthesis of protein compounds.

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

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Refer Que. no. 47 Page no. 319