Nucleic acid

       Nucleic acids are informational macromolecules. They are used by all organisms to store hereditary information that determines structural and functional characteristics. They are the only molecules in existence that can produce identical copies of themselves.

DNA and RNA are nucleotide polymers. A nucleotide subunit in both molecules contains a nitrogenous base, a five-carbon sugar, and a phosphate group. The only difference between their monomers is DNA contains the sugar deoxyribose, whereas RNA contains ribose.

      

Nitrogenous base in DNA: A, G, C, T

      

Nitrogenous base in RNA: A, G, C, U

C, T, U are single-ringed pyrimidines, while A, and G are larger double-ringed purines.

A single nucleotide polymer is called a strand. Covalent bonds are formed between the phosphate group of one nucleotide and the hydroxyl group attached to the number 3 carbon of the sugar on the adjacent nucleotide. A phosphate diester bond forms as the result of a condensation reaction between two –OH groups.

DNA is double stranded. The two strands are hold together by hydrogen bonds between nitrogenous bases on adjacent strands, and they are said to run antiparallel.

A—T

G—C

RNA molecules coil into a helix, but remain single stranded.

ATP is another type of nucleotide, which is used to drive virtually all the energy-requiring reactions in a cell. The hydrolysis of ATP is usually coupled with an endergonic process that attached the inorganic phosphate group to another molecule directly associated with the work the cell needs to do.