Glyceraldehyde (glyceral) is a
triose monosaccharide
Monosaccharides (from Greek ''monos'': single, '' sacchar'': sugar), also called simple sugars, are the simplest forms of sugar and the most basic units (monomers) from which all carbohydrates are built.
They are usually colorless, water-solub ...
with
chemical formula C3 H6 O3. It is the simplest of all common
aldose
An aldose is a monosaccharide (a simple sugar) with a carbon backbone chain with a carbonyl group on the endmost carbon atom, making it an aldehyde, and hydroxyl groups connected to all the other carbon atoms. Aldoses can be distinguished from keto ...
s. It is a
sweet, colorless,
crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macr ...
line
solid that is an intermediate compound in
carbohydrate metabolism. The word comes from combining
glycerol and
aldehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...
, as glyceraldehyde is glycerol with one
alcohol group oxidized to an aldehyde.
Structure
Glyceraldehyde has one
chiral center and therefore exists as two different
enantiomer
In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical ant ...
s with opposite optical rotation:
* In the
nomenclature, either from Latin ''Dexter'' meaning "right", or from Latin ''Laevo'' meaning "left"
* In the
R/S nomenclature, either R from Latin ''Rectus'' meaning "right", or S from Latin ''Sinister'' meaning "left"
While the
optical rotation
Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circul ...
of glyceraldehyde is (+) for ''R'' and (−) for ''S'', this is not true for all monosaccharides. The stereochemical configuration can only be determined from the chemical structure, whereas the optical rotation can only be determined
empirically (by experiment).
It was by a lucky guess that the molecular geometry was assigned to (+)-glyceraldehyde in the late 19th century, as confirmed by
X-ray crystallography in 1951.
Nomenclature
In the
system, glyceraldehyde is used as the configurational standard for carbohydrates. Monosaccharides with an absolute configuration identical to (''R'')-glyceraldehyde at the ''last'' stereocentre, for example C5 in
glucose, are assigned the stereo-descriptor . Those similar to (''S'')-glyceraldehyde are assigned an .
Chemical synthesis
Glyceraldehyde can be prepared, along with
dihydroxyacetone
Dihydroxyacetone (; DHA), also known as glycerone, is a simple saccharide (a triose) with formula .
DHA is primarily used as an ingredient in sunless tanning products. It is often derived from plant sources such as sugar beets and sugar cane ...
, by the mild oxidation of
glycerol, for example with
hydrogen peroxide and a
ferrous salt as
catalyst.
Its cyclohexylidene acetal can also be produced by oxidative cleavage of the bis(acetal) of
mannitol.
Biochemistry
The enzyme
glycerol dehydrogenase (NADP+) has two substrates,
glycerol and
NADP+, and 3 products, D-glyceraldehyde,
NADPH
Nicotinamide adenine dinucleotide phosphate, abbreviated NADP or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require NAD ...
and
H+.
The interconversion of the phosphates of glyceraldehyde (
glyceraldehyde 3-phosphate) and
dihydroxyacetone
Dihydroxyacetone (; DHA), also known as glycerone, is a simple saccharide (a triose) with formula .
DHA is primarily used as an ingredient in sunless tanning products. It is often derived from plant sources such as sugar beets and sugar cane ...
(
dihydroxyacetone phosphate), catalyzed by the
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
triosephosphate isomerase, is a intermediate step in
glycolysis
Glycolysis is the metabolic pathway that converts glucose () into pyruvate (). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH ...
.
See also
*
Stereoisomerism
References
{{Fructose and galactose metabolic intermediates
Vicinal diols
Trioses