Molecular Biology of the Cell by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter by by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morg

101
NOMENCLATURE A nucleoside or nucleotide is named according to its nitrogenous base.
Single-letter abbreviations are used variously as
base
BASE NUCLEOSIDE ABBR.
shorthand for (1) the base alone, (2) the
nucleoside, or (3) the whole nucleotide—
sugar
adenine adenosine A
the context will usually make clear which of
the three entities is meant. When the context BASE + SUGAR = NUCLEOSIDE
guanine
cytosine
guanosine
cytidine
G
C
is not sufficient, we will add the terms “base”,
“nucleoside”, “nucleotide”, or—as in the
examples below—use the full 3-letter nucleotide
base
code.
P
uracil uridine
U
AMP = adenosine monophosphate
dAMP = deoxyadenosine monophosphate
sugar
thymine thymidine T
UDP = uridine diphosphate
ATP = adenosine triphosphate BASE + SUGAR + PHOSPHATE = NUCLEOTIDE
NUCLEIC ACIDS
Nucleotides are joined together by a
phosphodiester linkage between 5’ and
3’ carbon atoms to form nucleic acids.
The linear sequence of nucleotides in a
nucleic acid chain is commonly
abbreviated by a one-letter code, such as
A—G—C—T—T—A—C—A, with the 5’
end of the chain at the left.
O
base
NUCLEOTIDES HAVE MANY OTHER FUNCTIONS
1 They carry chemical energy in their easily hydrolyzed phosphoanhydride bonds.
NH 2
phosphoanhydride bonds
N
N
O O O
–
N
O P O P O P O CH
N
2
O – O – O –
O
CH 2
O
sugar
example: ATP (or ATP )
OH
OH
– O P O
O –
+
O
O –
H 2 O
OH
CH 2
O
sugar
OH
base
2 They combine with other groups to form coenzymes.
H H O H H O H CH 3 H
HS C C N C C C N C C C C
H H H H H H HO CH 3 H
O
O P O
O –
O
P
O –
O
N
CH 2
N
O
N
N
O
O –
– O P O
O
5’ end of chain
5’
CH 2
sugar
base
example: coenzyme A (CoA)
3 They are used as specific signaling molecules in the cell.
O
O
NH 2
OH
P O –
O –
phosphodiester
linkage
– O P O O
3’ O
– O P O
example: cyclic AMP (cAMP)
N
NH 2
N
example: DNA
O
5’ CH 2
sugar
base
O
CH 2
O
N
N
3’ OH
3’ end of chain
O
P
O –
O
OH