Nucleic acids are large molecules (polymers) composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus.
They store genetic information and instruct the cell in creating proteins.
There are two types of nucleic acids:
Deoxyribonucleic Acid, DNA
Ribonucleic Acid, RNA
The three main types of RNA are:
Messenger RNA (mRNA)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
Nucleotides
Nucleic acids are composed of chains of nucleotides (monomers).
Nucleotides are made up of a sugar, a nitrogenous base, and a phosphate.
Nucleic Acid - DNA
DNA consists of two chains of nucleotides.
The two chains of nucleotides are formed in opposite directions.
The bonds and nitrogenous bases between the two sugar-phosphate backbones are shown.
Nucleic Acid - RNA
RNA is similar to DNA but only has a single chain of nucleotides (nucleobases).
It also has a different sugar and one different base.
Phosphodiester Bond
The bonds between nucleotides are called phosphodiester bonds.
Like bonds between monosaccharides, they are formed by dehydration synthesis reactions.
The carbon atoms are numbered, and the 3' carbon of one sugar bonds to the 5' carbon of the adjacent sugar through a phosphate group.
Nucleotide Sugars
RNA contains the sugar ribose, while DNA contains the sugar deoxyribose.
Bonds
The sugar on one nucleotide covalently bonds with the phosphate on the adjacent nucleotide to form a link in the nucleic acid molecule.
The nitrogen bases attach to a base on the other chain with hydrogen bonds.
Bonds and DNA Operation
Strong covalent bonds in the sugar-phosphate backbone create a strong molecule.
Weak hydrogen bonds allow the DNA molecule to be split, copied, and then put together.
Bases
RNA contains the bases adenine, guanine, cytosine, and uracil (A,G,C,U).
DNA contains the bases adenine, guanine, cytosine, and thymine (A,G,C,T).
The difference is that DNA uses thymine (T) rather than uracil (U).
Purines and Pyrimidines
Nitrogen-containing bases composed of 2-ringed structures are known as Purines.
Nitrogen-containing bases composed of 1-ringed structures are known as Pyrimidines.
DNA
DNA is double-stranded.
It forms a helix due to the angles of the strong sugar-phosphate bonds; hence, it is called a double helix.
Weak hydrogen bonding between nucleotides occurs in DNA between guanine (G) and cytosine (C) and between adenine (A) and thymine (T).
Nucleotide Sequence
Each strand is unique due to its sequence of bases.
Genetic information is stored in the sequence of nucleotides.
Since the bases are not part of the sugar or the phosphodiester bond, the base sequence is independent of the backbone.
Any base sequence is possible.
Double Helix
Instead of nucleotides being attracted to other bases in the same strand to create shapes, they bond to complementary nucleotides in a second strand to create the double-stranded helix.