Question

Glycosidic bonds exist in DNA molecule between
A.Sugar and phosphate
B.Any two nitrogen bases
C.Sugar and nitrogen base
D.Purines and pyrimidines

Answer 1

Hint: A Glycosidic bond is the bond between a sugar molecule and a nitrogen base to form a nucleoside. The bond between the molecules of DNA are different types of covalent bonds.

Complete answer:
DNA is De oxy ribo nucleic acid made up of Nucleotide molecule.A nucleotide consists of sugar molecule,phosphate and nitrogen bases bonded together.The sugar molecule in DNA IS DeOxyRibose sugar .The nitrogen bases are Adenine,Thymine,Guanine,Cytosine.DNA contains GENES that is the hereditary unit of our body.
The bond between the molecules of DNA are different types of covalent bonds. Covalent bond is a chemical bond formed by the sharing of electron pairs. An important type of covalent bond is glycosidic bond that exists between a sugar molecule to another group which may be a carbohydrate or any other group.Another type of covalent bond in DNA is a weak bond that is hydrogen bond. A strong bond also present in DNA that is the Ester bond that is the main structural backbone of DNA. Now let’s analyse the options one by one.

Option A)The bond between sugar and phosphate is an Ester bond. It forms the Sugar phosphate backbone and it is the main structural strength of DNA . Therefore this is an incorrect option
 Option B)Nitrogen bases in DNA are Adenine ,Thymine,Guanine,Cytosine.The bond between these nitrogen bases are simple covalent bonds that is Adenine with Thymine Double bond ,Guanine with Cytosine are triple bonds. Therefore this is an incorrect option
Option C)The sugar in DNA is DeOxyRibose sugar molecule.The nitrogen bases are attached to this sugar molecule through a special type of bond that is known as glycosidic bond. Therefore this is the correct option
Option D)In DNA Purines are Adenine and Guanine and Pyrimidines are Thymine and Cytosine.Purines are larger than Pyrimidines because Purines contain two ring structure while Pyrimidines have only a single ring.The bond between purines and pyrimidines are simple hydrogen bond, a weak covalent bond. Therefore this is an incorrect option

Hence, the correct answer is option (C)

Note: The deoxyribose sugar attached to a nitrogen base is known as Nucleoside .A Nucleoside attached to a phosphate group is a nucleotide. Hence the building blocks of DNA are known as nucleotide