In: Biology
Which bond can't be found in the structure of DNA?
a.Peptide bond
b.Hydrogen bond
c.Glycosidic bond
d.Phosphodiester bond
Answer: The bond which cannot be found in DNA is ‘a’ peptide bond.
Explanation: Peptide bond is formed between two amino acids. It is formed between carboxylic acid of one amino acid and amino group of another amino acid, by condensation reaction(with release of water molecule), the bond is depicted as –CO-NH-
DNA is a polynucleotide formed by many units of nucleotides. A single nucleotide consists of a Deoxyribose sugar, a nitrogen base and phosphoric acid.
Hydrogen bond is present between the complementary nitrogen bases of the two antiparallel strands of DNA molecule. It is a weak non covalent interaction between the nitrogen bases. Adenine pairs with thymine with double hydrogen bonds and vice versa. Guanine pairs with cytosine with triple hydrogen bonds.
Glycosidic bond is formed between the Deoxyribose sugar molecule and the nitrogen base. Glycosidic bonds are the covalent bonds which join the ring shaped sugar molecules with other molecules. In case of DNA if it is a purine ( adenine or guanine) nitrogen base then 9’ nitrogen of the base is linked to 1’carbon of the sugar molecule.
And if it is a pyrimidine (cytosine or thymine) nitrogen base then 1’nitrogen of the base is linked to the 1’carbon of the sugar molecule.
Phosphodiester bond is the covalent bond formed between the Deoxyribose sugar molecule and the phosphoric acid. In this the two hydroxyl groups of the phosphoric acid combine with the sugar molecules resulting in an ester bond formation. This way 5’ carbon of one sugar molecule is linked to the 3’carbon of another sugar molecule with the help of phosphodiester bond. With the help of phosphodiester bond formation the adjacent nucleotides in DNA are linked to each other.This bond forms the backbone of the DNA molec