3 Marks Question

Question 13 Marks

Give the plausible explanation for the following :
(a) Glucose does not give 2,4-DNP test.
(b) The two strands in DNA are not identical but are complementary.
(c) Starch and cellulose both contain glucose unit as monomer, yet they are structurally different.

Answer

(a) Due to cyclic structure of glucose- CHO group is not free.
(b) Because the hydrogen bonds are formed between specific pairs of basis.
(c) Starch is a polymer of $\alpha$-glucose while cellulose is a polymer of $\beta$-glucose.

View full question & answer→

Question 23 Marks

(a) Write the product when D-glucose reacts with conc. $HNO_3$.
(b) Amino acids show amphoteric behaviour. Why?
(c) Write one difference between $\alpha$-helix and $\beta$-pleated structures of proteins.

Answer

(a) $COOH -( CHOH )_4- COOH$
(b) Due to the presence of carboxyl and amino group in the same molecule/due to formation of zwitter ion or dipolar ion.
(c) $\alpha$-helix has intramolecular hydrogen bonding while $\beta$ pleated has intermolecular hydrogen bonding/ $\alpha$ helix results due to regular coiling of polypeptide chains while in $\beta$ pleated all polypeptide chains are stretched and arranged side by side.

View full question & answer→

Question 33 Marks

What are nucleic acids ?

Answer

Nucleic acids are molecular weight macropolymers. These are of mainly deoxyribose nucleic acid and ribose nucleic acid. These are also called polynucleotides, because these are polymers of long chains of nucleotides. Both types of nucleic acids have three main components pentose sugar, nitrogeneous base and phosphate group.
RNA molecules have ribose sugar, white DNA molecules have deoxyribose sugars. DNA have four bases : adenine (A), guanine (G), cytosine (C) and thyamine (T). First three bases of RNA are same but fourth base is uracil.
Nucleic acids are present in the nucleus of living cells. Genetic information of the living organisms is stored in nucleic acids.

View full question & answer→

Question 43 Marks

What are Carbohydrates? How are they classified?

Answer

Carbohydrates are polyhydroxy aldox or ketose which on hydrolysis gives monomer of glucose or fructose.
Depending upon the reaction of carbohydrates with water, they can be classified into :
(i) Monosaccharides : These cannot be hydrolysed. They contain aldehyde or ketone as the principal functional group.
Examples : glucose, fructose.

(ii) Disaccharides : Disaccharides on hydrolysis gives two monosaccharide molecules e.g., sucrose, lactose and maltose etc.
(iii) Polysaccharides : These are high molecular mass carbohydrates which on hydrolysis yield very large number of monosaccharides, e.g., starch and cellulose etc.

View full question & answer→

Question 53 Marks

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

View full question & answer→

Question 63 Marks

What is the difference between a nucleoside and a nucleotide ?

Answer

Nucleoside : A nucleoside contains only two basic components of nucleic acids i.e. a pentose sugar and a nitrogenous base.
Nitrogenous base + Pentose Sugar → Nucleoside
Depending upon the type of sugar present, nucleosides may be Riboside and Deoxyriboside.
Nucleotide: A nucleotide contains all the three basic components of nucleic acids i.e. $H _3 PO _4$, pentose sugar and a nitrogenous base.
OR
Nucleoside + Phosphoric acid → Nucleotide
Depending upon the type of sugar present, nucleotides like nucleosides are of two types:
(i) Ribonucleotides, (ii) Deoxyribonucleotides.

View full question & answer→

Question 73 Marks

Why is fructose a reducing sugar?

Answer

The reaction with Tollen's reagent is carried out in the basic medium in which fructose is convert into enolic form which exists in equilibrium with glucose. Thus fructose behaves as a reducing sugar.

View full question & answer→

Question 83 Marks

How will you convert fructose into glucose?

View full question & answer→

Question 93 Marks

What do you understand by the glucosidic linkage?

Answer

The two monosaccharide molecules are joined together by an oxide linkage formed by the loss of water molecule. Such a linkage between two monosaccharide units through oxygen atom is called glycosidic linkage. This glycosidic linkage is also present in polysaccharides like starch and cellulose. For example, the glycosidic linkage in maltose molecule is shown below :

View full question & answer→

Chemistry 3 Marks Question

Test yourself on this topic