CHEMISTRY GLOSSARY

glucose    →   glukoza

Glucose (grape sugar, blood sugar), C₆H₁₂O₆, is an aldohexose (a monosaccharide sugar having six carbon atoms and an aldehyde group). An older common name for glucose is dextrose, after its dextrorotatory property of rotating plane polarized light to the right. Glucose in free (in sweet fruits and honey) or combined form (sucrose, starch, cellulose, glycogen) is is probably the most abundant organic compound in nature. During the photosynthesis process, plants use energy from the sun, water from the soil and carbon dioxide gas from the air to make glucose. In cellular respiration, glucose is ultimately broken down to yield carbon dioxide and water, and the energy from this process is stored as ATP molecules (36 molecules of ATP across all processes).

Naturally occurring glucose is D isomers (OH group on the stereogenic carbon farthest from the aldehyde group, C-5, is to the right in the Fischer projection). Although often displayed as an open chain structure, glucose and most common sugars exist as ring structures. In the α form, the hydroxyl group attached to C-1 and the CH₂OH attached to C-5 are located on opposite sides of the ring. β-glucose has these two groups on the same side of the ring. The full names for these two anomers of glucose are α-D-glucopyranose and β-D-glucopyranose.

glycogen    →   glikogen

Glycogen (animal starch) is a polysaccharide that serves the same energy storage function in animals that starch serves in plants. Dietary carbohydrates not needed for immediate energy are converted by the body to glycogen for long term storage (principally in muscle and liver cells). Like amylopectin found in starch, glycogen is a polymer of α(1→4)-linked subunits of glucose, with α(1→6)-linked branches. Glycogen molecules are larger than those of amylopectin (up to 100 000 glucose units) and contain even more branches. Branch points occur about every 10 residues in glycogen and about every 25 residues in amylopectin. The branching also creates lots of ends for enzyme attack and provides for rapid release of glucose when it is needed.

water softening    →   omekšavanje vode

Water softening is a process in which calcium and magnesium ions are removed from water. It is usually done by ion exchanger which exchanges removed ions with sodium ones.

glycon    →   glikon

Glycon (glycone) is the sugar component of the glycoside. The link between the glycon and aglycon is known as glycosidic bond.

glycoside    →   glikozid

Glycoside is one of a group of organic compounds in which a sugar group is bonded through its anomeric carbon to another group via a glycosidic bond. The sugar group is known as the glycon and the non-sugar group as the aglycon. According to the IUPAC definition, all disaccharides and polysaccharides are glycosides where the aglycone is another sugar.

In the free hemiacetal form, sugars will spontaneously equilibrate between the α and β anomers. However, once the glycosidic bond is formed, the anomeric configuration of the ring is locked as either α or β. Therefore, the alpha and beta glycosides are chemically distinct. They will have different chemical, physical, and biological properties. Many glycosides occur abundantly in plants, especially as flower and fruit pigments.

The term glycoside was later extended to cover not only compounds in which the anomeric hydroxy group is replaced by a group -OR, but also those in which the replacing group is -SR (thioglycosides), -SeR (selenoglycosides), -NR1R2 (N-glycosides), or even -CR1R2R3 (C-glycosides). Thioglycoside and selenoglycoside are legitimate generic terms; however the use of N-glycoside, although widespread in biochemical literature, is improper and not recommended here (glycosylamine is a perfectly acceptable term). C-Glycoside is even less acceptable. All other glycosides are hydrolysable; the C-C bond of C-glycosides is usually not. The use and propagation of names based on C-glycoside terminology is therefore strongly discouraged.

wavefunction    →   valna funkcija

Wavefunction (Ψ) is a mathematical function that gives the amplitude of a wave as a function of position (and sometimes as a function of time and/or electron spin). Wavefunctions are used in chemistry to represent the behaviour of electrons bound in atoms or molecules.

half-wave potential    →   poluvalni potencijal

Half-wave potential (E_1/2) is a potential at which polarographic wave current is equal to one half of diffusion current (i_d). In a given supporting electrolyte, the half-wave potential is unique for each element and its different valence states and chemical forms. Observation of a current peak at a specific half-wave potential therefore identifies the chemical species producing the current.

hydration    →   hidratacija

Hydration is addition of water or the elements of water (i.e. H and OH) to a molecular entity. The term is also used in a more restricted sense for the process:

hydrogen    →   vodik

Hydrogen was discovered by Sir Henry Cavendish (England) in 1766. The origin of the name comes from the Greek words hydro and genes meaning water and generate. It is colourless, odourless gas, burns and forms explosive mixtures in air. Reacts violently with oxidants. Hydrogen is the most abundant element in the universe. Commercial quantities of hydrogen are produced by reacting superheated steam with methane or carbon. In lab work from reaction of metals with acid solutions or electrolysis. Most hydrogen is used in the production of ammonia and in metal refining. Also used as fuel in rockets. Its two heavier isotopes (deuterium and tritium) used respectively for nuclear fusion.

white spirit    →   bijeli špirit

White spirit (mineral spirits, petroleum spirits) is a paraffin-derived clear, transparent liquid which is a common organic solvent used in painting and decorating.