Question

How do nucleic acids interact with water?

Answer 1

Hint: Nucleic acids are an essential form of life that stores- and expresses the genetic information of organisms. They are present in all cells and viruses in the form of DNA or RNA.

Complete answer:
Nucleic acids are large macromolecules made by the monomer units of nucleotides. Nucleotides are the building block of nucleic acids that consist of a sugar molecule, a phosphate group, and nitrogenous bases. The nucleotides bind with each other through a phosphodiester linkage to form nucleic acids. The linkage is formed between the phosphorus group of one nucleotide and the -OH group of the other nucleotide.

They are the main information-carrying molecules of the cell and contain the genetic information of an organism. They also direct the synthesis of proteins in the cells of the body. The two main types of nucleic acids found are- DNA (Deoxyribonucleic acids) and RNA (Ribonucleic acids). The major difference between their structures lies in the sugar and the nitrogenous bases present. The sugar molecule present in RNA is ribose, while the sugar molecule present in the DNA is deoxyribose. The nitrogenous bases present in the DNA and RNA are all the same, except for one. RNA has the nitrogenous base Uracil in place of the nitrogenous base Thymine.
The phosphate group and the sugar molecule present in the nucleic acids are hydrophilic or water-loving substances. The nitrogenous bases are generally hydrophobic but they do form hydrogen bonds during the double helix structure of the DNA. The two nitrogenous bases on the two strands of double-stranded DNA molecules are attached through hydrogen bonds.

The adenine nitrogenous base attaches itself to the thymine/uracil nitrogenous base through two hydrogen bonds. The guanine nitrogenous base attaches itself to the cytosine nitrogenous base through three hydrogen bonds. The hydrogen bonds present between these nitrogenous bases hold the two strands of the DNA molecule together. A single strand of RNA molecules also forms the double helix structure through these hydrogen bonds.
The nucleic acids are generally polar and can easily dissolve in water. The nitrogenous bases are hydrophobic and are kept away from water through the double helix structure. This structure brings the nitrogenous bases to the center of the structure. The phosphate group and the sugar molecules can easily dissolve in water. The nucleic acids interact with water to form their double helix structure.

Water also helps in the stabilization of the RNA and DNA molecules. It eliminates the electrostatic repulsion between the two phosphate groups by its high dielectric constant. Water also forms a hydration shell around the double-helical structure, near the phosphate groups. The hydration is observed more in RNA molecules- as compared to DNA molecules.

Note: The three-dimensional double-helical structure of DNA molecules was given by James Watson and Francis Crick in 1953. The basis of their model came from the X-ray crystallography experiment of Rosalind Franklin. The two strands of DNA run antiparallel to each other. They are complementary to each other due to complementary base pairing.