Dictionary of Chemistry [6th Ed.]

R-isomer 464

r

R-isomerSee absolute configura-

tion.

RMESee biofuel.

RNA(ribonucleic acid)A complex or-

ganic 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 nu-

cleus and then distributed to various

parts of the cytoplasm. An RNA mol-

ecule consists of a long chain of *nu-

cleotides in which the sugar is

*ribose and the bases are adenine,

cytosine, guanine, and uracil (see il-

lustration). Compare dna.

roasting The heating of aÜnely

ground ore, especially a sulphide, in

air prior to *smelting. The roasting

G

A U G A

A

G

U

U

G

A

A C U

U

C

A

U

G

G

A

G

U

A

G

C

A

G A

U A G C

G C

bases

sugar–phosphate backbone

Single-stranded structure of RNA

P

O–

O–

O O CH 2

O

OOH

P

O–

O O CH 2

O

OOH

P

O–

O O CH 2

O

OOH

P

O–

OOCH 2

O

OH OH

nucleotide

ribose

basesbasesbases

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

HC NH

HC

O

O

C

N

H

C

HC N

HC

NH 2

O

C

N

C

C NH

C

O

NH 2

C

N

CH

C N

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