CHEMISTRY GLOSSARY

standard electrode potential    →   standardni elektrodni potencijal

Standard electrode potential (E°) (standard reduction potentials) are defined by measuring the potential relative to a standard hydrogen electrode using 1 mol solution at 25 °C. The convention is to designate the cell so that the oxidised form is written first. For example,

The e.m.f. of this cell is -0.76 V and the standard electrode potential of the Zn²+|Zn half cell is -0.76 V.

standard hydrogen electrode    →   standardna vodikova elektroda

Standard hydrogen electrode is a system in which hydrogen ion and gaseous hydrogen are present in their standard states. The convention is to designate the cell so that the standard hydrogen electrode is written first.

The electrode is used as a reference (of zero) for the values of other standard electrode potentials.

starch    →   škrob

Starch (C₆H₁₀O5)_x is a polysaccharide used by plants to stockpile glucose molecules. It is the major component of flour, potatoes, rice, beans, corn, and peas. Starch is a mixture of two different polysaccharides: amylose (about 20 %), which is insoluble in cold water, and amylopectin (about 80 %), which is soluble in cold water. Amylose is composed of unbranched chains of D-glucose units joined by α(1→4)-glycosidic linkages. Unlike amylose, which are linear polymers, amylopectin contains α(1→6)-glycoside branches approximately every 25 glucose units.

Starch digestion begins in the mouth via the action of amylase, a digestive enzyme present in saliva. The process is completed in the small intestine by the pancreatic amylase. The final products of starch digestion, glucose molecules, are absorbed into the intestinal bloodstream and transported to the liver. Like most enzymes, glycosidases are highly selective in their action. They hydrolyze only the α-glycoside links in starch and leave the β-glycoside links in cellulose untouched. Starch is important food stuff and is used in adhesives, and sizes, in laundering, pharmacy and medicine.

strontium    →   stroncij

Strontium was discovered by Sir Humphry Davy (England) in 1808. Named after the village of Strontian in Scotland. It is soft, malleable, silvery-yellow metal. Combustible in air, will react with water. Exposed surfaces form protective oxide film. Metal ignites and burns readily. Strontium is found in minerals celestite and strontianite. Used in flares and fireworks for crimson colour. Strontium-90 is a long lived highly radioactive fallout product of atomic-bomb explosions.

thorium    →   torij

Thorium was discovered by Jöns Jakob Berzelius (Sweden) in 1828. Named after Thor, the mythological Scandinavian god of war. It is heavy, grey, soft, malleable, ductile, radioactive metal. Tarnishes in air; reacts with water. Reacts violently with oxidants. Thorium is found in various minerals like monazite and thorite. Used in making strong alloys. Also in ultraviolet photoelectric cells. It is a common ingredient in high-quality lenses. Bombarded with neutrons make uranium-233, a nuclear fuel.

threonine    →   treonin

Threonine is neutral amino acids with polar side chains. It differs from serine by having a methyl substituent in place of one of the hydrogens on the β carbon. Threonine is a site of phosphorylation and glycosylation which is important for enzyme regulation and cell signaling. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested.

• Abbreviations: Thr, T
• IUPAC name: 2-amino-3-hydroxybutanoic acid
• Molecular formula: C₄H₉NO₃
• Molecular weight: 119.12 g/mol

triclinic lattice    →   triklinska rešetka

Triclinic lattice has one lattice point at the each corner of the unit cell. It has unit cell vectors a≠b≠c and interaxial angles α≠β≠γ≠90°.

tyrosine    →   tirozin

Tyrosine is hydrophobic amino acids with aromatic side chain. Tyrosine is large aromatic residue that is normally found buried in the interior of a protein and is important for protein stability. Tyrosine has special properties since its hydroxyl side chain may function as a powerful nucleophile in an enzyme active site (when ionized) and is a common site for phosphorylation in cell signaling cascades. Tyrosine absorbs ultraviolet radiation and contributes to the absorbance spectra of proteins. It is not essential (or semi-essential) to the human diet, since it is synthesized in the body from other metabolites.

• Abbreviations: Tyr, Y
• IUPAC name: 2-amino-3-(4-hydroxyphenyl)propanoic acid
• Molecular formula: C₉H₁₁NO₃
• Molecular weight: 181.19 g/mol

ultraviolet light    →   ultraljubičasto svjetlo

Ultraviolet light (UV light or UV radiation) is an electromagnetic radiation with a wavelength longer than that of x-rays, but shorter than that of visible light. Ultraviolet light can break some chemical bonds and cause cell damage.

zinc    →   cink

Zinc was discovered by Andreas Marggraf (Germany) in 1746. The origin of the name comes from the German word zink. It is bluish-silver, ductile metal. Reacts with alkalis and acids. Tarnishes in air. Zinc is found in the minerals zinc blende (sphalerite) (ZnS), calamine, franklinite, smithsonite (ZnCO₃), willemite and zincite (ZnO). Used to coat other metal (galvanizing) to protect them from rusting. Although some 90 % of the zinc is used for galvanizing steel. Zinc metal is used in the common dry-cell battery. Also used in alloys such as brass, bronze. Zinc compounds are also used in the manufacture of paints, cosmetics, plastics, electronic devices, and other products.