R-isomer
464
r
R-isomer See absolute configuration.
RME See biofuel.
RNA (ribonucleic acid) A complex organic compound (a nucleic acid) in
living cells that is concerned with
*protein synthesis. In some viruses,
RNA is also the hereditary material.
Most RNA is synthesized in the nucleus and then distributed to various
parts of the cytoplasm. An RNA molecule consists of a long chain of *nucleotides in which the sugar is
*ribose and the bases are adenine,
cytosine, guanine, and uracil (see illustration). Compare dna.
roasting The heating of a Ünely
ground ore, especially a sulphide, in
air prior to *smelting. The roasting
G
A
U G
A
A
G
U
U
G
A
U
C
A
U
C
A
U
G
G
A
G
U
A
G
C
A
A
G U A
G C
G
C
bases
sugar–phosphate backbone
Single-stranded structure of RNA
P
O –
O –
O
O CH 2
O
O OH
P
O –
O
O CH 2
O
O OH
P
O –
O
O CH 2
O
O OH
P
O –
O
O C H 2
O
OH OH
nucleotide
ribose
bases bases bases
Detail of molecular structure of sugar–
phosphate backbone. Each ribose unit is
attached to a phosphate group and a base,
forming a nucleotide.
C
N
H
C
NH
HC
HC
O
O
C
N
H
C
N
HC
HC
NH 2
O
C
N
C
NH
C
C
O
NH 2
C
N
CH
N
C
C
NH 2
N
N
H
HC
N
N
H
HC
adenine
(A)
guanine
(G)
cytosine
(C)
uracil
(U)
The four bases of RNA
RNA
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