In the nucleotides, while the heterocyclic base is linked to C-1 of the
sugar through an N-glycosidic b-linkage, the phosphoric acid is bonded by a
phosphate ester linkage to C-5. When the sugar is a part of a nucleoside, the
numbering of sugars starts with 1
0 , i.e. C-1 becomes C-1
0 , for example 2
0 -
deoxyadenosine 5
0 -phosphate and uridine 5
0 -phosphate.
P
O
O
O
N
N
O
OH
O
N
N
NH 2
P
O
O
O
O
OH
O
OH
N
N
O
H
O
2'-Deoxyadenosine 5'-phosphate
Adenine
Deoxyribose
Phosphate
1'
2'
3'
4'
5'
Uridine 5'-phosphate
Uracil
Ribose
Phosphate
1'
2'
3'
4'
5'
2'-Deoxyadenosine
Uridine
Despite being structurally similar, DNA and RNA differ in size and in their
functions within a cell. The molecular weights of DNA, found in the nucleus
of cells, can be up to 150 billion and lengths up to 12 cm, whereas the
molecular weight of RNA, found outside the cell nucleus, can only be up to
35 000.
Deoxyribonucleic acid (DNA)
Name of the nucleotide
Composition
2
0 -Deoxyadenosine 5
0 -phosphate
Adenine + deoxyribose + phosphate
Nucleoside is 2
0 -deoxyadenosine, composed of
adenine and deoxyribose
2
0 -Deoxyguanosine 5
0 -phosphate
Guanine + deoxyribose + phosphate
Nucleoside is 2
0 -deoxyguanosine, composed of
guanine and deoxyribose
2
0 -Deoxycytidine 5
0 -phosphate
Cytosine + deoxyribose + phosphate
Nucleoside is 2
0 -deoxycytidine, composed of
cytosine and deoxyribose
2
0 -Deoxythymidine 5
0 -phosphate
Thymine + deoxyribose + phosphate
Nucleoside is 2
0 -deoxythymidine, composed of
thymine and deoxyribose
Ribonucleic acid (RNA)
Adenosine 5
0 -phosphate
Adenine + ribose + phosphate
Nucleoside is adenosine, composed of adenine and ribose
Guanosine 5
0 -phosphate
Guanine + ribose + phosphate
Nucleoside is guanosine, composed of guanine and ribose
Cytidine 5
0 -phosphate
Cytosine + ribose + phosphate
Nucleoside is cytidine, composed of cytosine and ribose
Uridine 5
0 -phosphate
Uracil + ribose + phosphate
Nucleoside is uridine, composed of uracil and ribose
4.8.1 Synthesis of nucleosides and nucleotides
A reaction between a suitably protected ribose or 2-deoxyribose and an
appropriate purine or pyrimidine base yields a nucleoside. For example,
4.8 NUCLEIC ACIDS
171
sugar through an N-glycosidic b-linkage, the phosphoric acid is bonded by a
phosphate ester linkage to C-5. When the sugar is a part of a nucleoside, the
numbering of sugars starts with 1
0 , i.e. C-1 becomes C-1
0 , for example 2
0 -
deoxyadenosine 5
0 -phosphate and uridine 5
0 -phosphate.
P
O
O
O
N
N
O
OH
O
N
N
NH 2
P
O
O
O
O
OH
O
OH
N
N
O
H
O
2'-Deoxyadenosine 5'-phosphate
Adenine
Deoxyribose
Phosphate
1'
2'
3'
4'
5'
Uridine 5'-phosphate
Uracil
Ribose
Phosphate
1'
2'
3'
4'
5'
2'-Deoxyadenosine
Uridine
Despite being structurally similar, DNA and RNA differ in size and in their
functions within a cell. The molecular weights of DNA, found in the nucleus
of cells, can be up to 150 billion and lengths up to 12 cm, whereas the
molecular weight of RNA, found outside the cell nucleus, can only be up to
35 000.
Deoxyribonucleic acid (DNA)
Name of the nucleotide
Composition
2
0 -Deoxyadenosine 5
0 -phosphate
Adenine + deoxyribose + phosphate
Nucleoside is 2
0 -deoxyadenosine, composed of
adenine and deoxyribose
2
0 -Deoxyguanosine 5
0 -phosphate
Guanine + deoxyribose + phosphate
Nucleoside is 2
0 -deoxyguanosine, composed of
guanine and deoxyribose
2
0 -Deoxycytidine 5
0 -phosphate
Cytosine + deoxyribose + phosphate
Nucleoside is 2
0 -deoxycytidine, composed of
cytosine and deoxyribose
2
0 -Deoxythymidine 5
0 -phosphate
Thymine + deoxyribose + phosphate
Nucleoside is 2
0 -deoxythymidine, composed of
thymine and deoxyribose
Ribonucleic acid (RNA)
Adenosine 5
0 -phosphate
Adenine + ribose + phosphate
Nucleoside is adenosine, composed of adenine and ribose
Guanosine 5
0 -phosphate
Guanine + ribose + phosphate
Nucleoside is guanosine, composed of guanine and ribose
Cytidine 5
0 -phosphate
Cytosine + ribose + phosphate
Nucleoside is cytidine, composed of cytosine and ribose
Uridine 5
0 -phosphate
Uracil + ribose + phosphate
Nucleoside is uridine, composed of uracil and ribose
4.8.1 Synthesis of nucleosides and nucleotides
A reaction between a suitably protected ribose or 2-deoxyribose and an
appropriate purine or pyrimidine base yields a nucleoside. For example,
4.8 NUCLEIC ACIDS
171