Physicochemical Properties of Monosaccharides

A set of vocabulary flashcards covering the physical properties, chemical reactivity, and biologically significant structures of monosaccharides and their derivatives.

Monosaccharide Solubility

The physical property of monosaccharides being water-soluble due to multiple hydroxyl ($-\text{OH}$) groups, soluble in methanol, and insoluble in ether, forming viscous syrups in concentrated aqueous solutions.

Caramelization

The thermal degradation of monosaccharides upon heating (for example, glucose melting and beginning to decompose at around $150\,^\circ\text{C}$), which prevents their separation by gas chromatography (GC).

Infrared Spectrum of Monosaccharides

The characteristic absorption spectrum exhibited by monosaccharides used for their identification, as they do not absorb light in the visible or ultraviolet regions.

Biot's Law

A physical law of optical rotation that allows the polarimetric quantitative determination of monosaccharides.

Furfural Derivatives

Cyclic compounds formed through the internal dehydration of monosaccharides in concentrated acidic media under heat, capable of condensing with phenols or aromatic amines to produce colored identification complexes.

Epimerization and Interconversion

Chemical reactions occurring in an alkaline medium at low temperatures where monosaccharides interconvert between aldose and ketose forms or invert configuration at carbon $2$; at high temperatures, complete degradation occurs.

Aldonic Acids

Monocarboxylic sugar acids produced when the aldehyde function of an aldose is oxidized by mild oxidizing agents such as bromine, iodine in an alkaline medium, or dilute nitric acid (e.g., glucose yielding gluconic acid).

Aldaric Acids

Dicarboxylic sugar acids containing carboxyl groups at both carbons $1$ and $6$, formed by extensive oxidation of aldoses using strong oxidizing agents like hot nitric acid ($\text{HNO}_3$).

Fehling's Solution Reaction

An oxidation-reduction reaction in an alkaline medium where an aldose reduces cupric oxide (blue) to insoluble cuprous oxide ($\text{Cu}_2\text{O}$, brick red) while oxidizing to an aldonic acid, used to detect reducing sugars in biological fluids.

Polyols

Sugar alcohols produced by the reduction of monosaccharides via either a reversible enzymatic pathway catalyzed by reductases or an irreversible chemical pathway using catalytic hydrogenation or sodium borohydride ($\text{NaBH}_4$).

$N$-Glycosides (Cyclic Imines)

Substitution products formed by the condensation of aldoses or ketoses with amines, serving as essential structural units of nucleosides and nucleotides.

$S$-Glycosides (Thio-glycosides)

Substitution products formed by the reaction of aldoses with thiols ($\text{HS-R}$); ketoses do not undergo this reaction.

$O$-Glycosides

Compounds formed by the reaction of monosaccharides with alcohols or phenols (such as methanol with glucose) that lack reducing power and are incapable of mutarotation.

Permethylation

The complete methylation of all free hydroxyl groups (both alcoholic and hemiacetal) of a monosaccharide using reagents such as $\text{ICH}_3$ with $\text{Ag}_2\text{O}$ or $(\text{CH}_3)_2\text{SO}_4$ with $\text{NaOH}$.

Uronic Acids

Sugar acids formed by the selective oxidation of the primary alcohol function of a monosaccharide while the carbonyl group is protected, such as glucuronic acid produced from glucose via UDP-glucose dehydrogenase.

Urono-conjugates

In vivo complexes formed between uronic acids and toxic substances that enable the elimination of toxins from the body.

Triose Phosphates

Glyceraldehyde 3-phosphate and dihydroxyacetone phosphate, the metabolic triose derivatives formed by the aldolase-catalyzed cleavage of fructose-1,6-bisphosphate in glycolysis.

D-Erythrose-4-Phosphate

The sole tetrose derivative of metabolic interest, functioning as an essential intermediate in the pentose phosphate pathway.

L-Arabinose

A naturally occurring plant pentose belonging to the rare L-series of sugars, contrasted with D-arabinose which is an immediate precursor of D-glucose and D-mannose that is excreted directly in human urine.

Sedoheptulose

The only biologically significant seven-carbon ketose, functioning in photosynthesis and the pentose phosphate pathway in the form of sedoheptulose-7-phosphate.

Hexosamines (Osamines)

Monosaccharide derivatives in which a hydroxyl group (typically at carbon $2$) is replaced by an amino group, exhibiting both reducing sugar and basic amine properties in chitin, murein, glycoproteins, and glycolipids.

L-Ascorbic Acid (Vitamin C)

The lactone of L-gulonic acid derived from the aldohexose L-gulose, functioning as an essential cofactor in cellular redox reactions through reversible conversion to dehydroascorbic acid.