CHEMISTRY GLOSSARY
glass electrode → staklena elektroda
Glass electrode is a hydrogen-ion responsive electrode usually consisting of a bulb, or other suitable form, of special glass attached to a stem of high resistance glass complete with internal reference electrode and internal filling solution system. Glass electrode is also available for the measurement of sodium ions.
The glass electrode, which consists of a thin wall glass bulb, has an extremely high electrical resistance. The membrane of a typical glass electrode (with a thickness of 0.03 mm to 0.1 mm) has an electrical resistance of 30 MΩ to 600 MΩ. The surface of a glass membrane must be hydrated before it will function as a pH electrode. When a glass surface is immersed in an aqueous solution then a thin solvated layer (gel layer) is formed on the glass surface in which the glass structure is softer. This applies to both the outside and inside of the glass membrane.
The simplest explanation for the working of the thin glass electrode is that the glass acts as a weak acid (Glass-H).
The hydrogen ion activity of the internal solution is held constant. When a solution of different pH from the inside comes in contact with the outside of the glass membrane, the glass is either deprotonated or protonated relative to the inside of the glass. The difference in pH between solutions inside and outside the thin glass membrane creates electromotive force in proportion to this difference in pH.
glutamine → glutamin
Glutamine is neutral amino acids with polar side chains. It serves as an important carrier of ammonia and contributes it to the formation of urea and purines. Glutamine is not recognized as an essential amino acid but may become conditionally essential in certain situations, including intensive athletic training or certain gastrointestinal disorders. It is synthesized by the enzyme glutamine synthetase from glutamate and ammonia.
- Abbreviations: Gln, Q
- IUPAC name: 2,5-diamino-5-oxopentanoic acid
- Molecular formula: C5H10N2O3
- Molecular weight: 146.14 g/mol
glycine → glicin
Glycine is the smallest amino acid and is unique because it lacks a side chain. This gives it more conformational freedom than any other amino acid. Glycine is often found in turns and loops where other amino acids would be sterically unacceptable. Although it is formally nonpolar, it’s very small side chain makes no real contribution to hydrophobic interactions. Glycine is not essential to the human diet, as it is biosynthesized in the body from the amino acid serine.
- Abbreviations: Gly, G
- IUPAC name: 2-aminoacetic acid
- Molecular formula: C2H5NO2
- Molecular weight: 75.07 g/mol
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.
gold → zlato
Gold has been known since ancient times. The origin of the name comes from the Latin word aurum meaning gold. It is soft, malleable, bright yellow metal. Unaffected by air, water, alkalis and most acids. Gold is found in veins in the crust, with copper ore and native. Used in electronics, jewellery and coins. It is a good reflector of infrared radiation, so a thin film of gold is applied to the glass of skyscrapers to reduce internal heating from sunlight.
gravimetry → gravimetrija
Gravimetry is the quantitative measurement of an analyte by weighing a pure, solid form of the analyte. Since gravimetric analysis is an absolute measurement, it is the principal method for analysing and preparing primary standards.
A typical experimental procedure to determine an unknown concentration of an analyte in a solution is as follows:
- quantitatively precipitate the analyte from the solution
- collect the precipitate by filtering and wash it to remove impurities
- dry the solid in an oven to remove the solvent
- weigh the solid on an analytical balance
- calculate the analyte concentration in the original solution based on the weight of the precipitate.
overpotential → prenapon
Overpotential (η) is a potential that must be applied in an electrolytic cell in addition to the theoretical potential required to liberate a given substance at an electrode. The value depends on the electrode material and on the current density.
Citing this page:
Generalic, Eni. "Bronsted-Lowry’s acid - base theory." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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