NUCLEOTIDES AND NUCLEIC ACIDS
(a) the structure of a nucleotide as the monomer from which nucleic acids are made
● To include the differences between RNA and DNA nucleotides, the
identification of the purines and pyrimidines and the type of pentose sugar.
Nucleotides, the monomers of nucleic acids, of which there are two types, have an
identical, general, 3-part structure. It is based off a phosphate ‘backbone’ of
phosphate group (H3PO4), which is the same in all nucleotides, covalently bonded to
a pentose sugar, which can be ribose or deoxyribose, and then one of five
nitrogenous bases.
These bases form into two categories, the purines, bases made up of one six-
sided ring structure and one five-sided ring, such as guanine and adenine, or made
up of just one six-sided ring, a pyrimidine, such as thymine, cytosine and uracil.
DNA RNA
Formed in the nucleus Formed in the nucleus
Predominantly found in the nucleus Found throughout the cell
Double strand of nucleotides -coiled into a Single strand of nucleotides, which can fold into
double helix. The two strands are linked by different shapes.
hydrogen bonding between the bases
Cytosine with Guanine, Adenine with Thymine
Pentose sugar present - Deoxyribose Pentose sugar present - Ribose
Bases present: Cytosine, Bases present: Cytosine,
Guanine, Adenine, Thymine Guanine, Adenine, Uracil
Larger molecule Smaller molecule
One basic form Three main forms: messenger
RNA, transfer RNA, ribosomal
RNA
Ratio of 1:1 for adenine:thymine, Ratio of adenine:thymine, and
and cytosine:guanine cytosine:guanine variable
(b) The synthesis and breakdown of polynucleotides by the formation and breakage of
phosphodiester bonds.
Nucleotides are linked together by condensation reactions to form polynucleotides, a
polymer. The phosphate group at the fifth carbon on the pentose sugar (5’) of one
nucleotide forms a covalent bond with the hydroxyl group of the third carbon (3’) of
an adjacent nucleotide. As they occur between a phosphate group and two pentose
sugars, they are called phosphodiester bonds. When many of the reactions take
place, a polynucleotide is formed with a strong, sugar-phosphate ‘backbone’. This
reaction is catalysed by DNA polymerase and DNA ligases in DNA replication.
(a) the structure of a nucleotide as the monomer from which nucleic acids are made
● To include the differences between RNA and DNA nucleotides, the
identification of the purines and pyrimidines and the type of pentose sugar.
Nucleotides, the monomers of nucleic acids, of which there are two types, have an
identical, general, 3-part structure. It is based off a phosphate ‘backbone’ of
phosphate group (H3PO4), which is the same in all nucleotides, covalently bonded to
a pentose sugar, which can be ribose or deoxyribose, and then one of five
nitrogenous bases.
These bases form into two categories, the purines, bases made up of one six-
sided ring structure and one five-sided ring, such as guanine and adenine, or made
up of just one six-sided ring, a pyrimidine, such as thymine, cytosine and uracil.
DNA RNA
Formed in the nucleus Formed in the nucleus
Predominantly found in the nucleus Found throughout the cell
Double strand of nucleotides -coiled into a Single strand of nucleotides, which can fold into
double helix. The two strands are linked by different shapes.
hydrogen bonding between the bases
Cytosine with Guanine, Adenine with Thymine
Pentose sugar present - Deoxyribose Pentose sugar present - Ribose
Bases present: Cytosine, Bases present: Cytosine,
Guanine, Adenine, Thymine Guanine, Adenine, Uracil
Larger molecule Smaller molecule
One basic form Three main forms: messenger
RNA, transfer RNA, ribosomal
RNA
Ratio of 1:1 for adenine:thymine, Ratio of adenine:thymine, and
and cytosine:guanine cytosine:guanine variable
(b) The synthesis and breakdown of polynucleotides by the formation and breakage of
phosphodiester bonds.
Nucleotides are linked together by condensation reactions to form polynucleotides, a
polymer. The phosphate group at the fifth carbon on the pentose sugar (5’) of one
nucleotide forms a covalent bond with the hydroxyl group of the third carbon (3’) of
an adjacent nucleotide. As they occur between a phosphate group and two pentose
sugars, they are called phosphodiester bonds. When many of the reactions take
place, a polynucleotide is formed with a strong, sugar-phosphate ‘backbone’. This
reaction is catalysed by DNA polymerase and DNA ligases in DNA replication.
