CHEMISTRY GLOSSARY

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

actinium    →   aktinij

Actinium was discovered by André Debierne (France) in 1899. The origin of the name comes from the Greek word aktinos meaning ray. It is heavy, silvery-white, very radioactive metal. Reacts with water. Glows in the dark. Actinium is extremely rare, found in all uranium ores. Usually obtained by treating radium with neutrons in a reactor.

activity    →   aktivitet

Activity (a) is a thermodynamic function used in place of concentration in equilibrium constants for reactions involving nonideal gases and solutions. For the species i activity is defined as

where a_i is the activity of the species i, c_i is its molar concentration, and f_i is a dimensionless quantity called the activity coefficient.

adrenaline    →   adrenalin

Adrenaline was the first naturally produced hormone to be isolated in its pure state. It is known as epinephrine, but its chemical name is 1-[3,4-dihydroxyphenol]-2-methylaminoethanol. Adrenaline is a hormone, produced by the medulla of the adrenal glands, that increases heart activity, improves the power and prolongs the action of muscles, and increases the rate and depth of breathing to prepare the body for "fright, flight, or fight". At the same time it inhibits digestion and excretion.

cation exchange    →   kationski izmjenjivač

Cation exchange is a cationic resin has positive ions built into its structure and therefore exchanges negative ions. In the cation exchange, the side groups are ionised acidic groups, such as (-SO₃H, -COOH, -OH) to which cations H⁺ are attached. The exchange reaction is one in which different cations in the solution displace the H⁺ from the solid.

detergent    →   deterdžent

Detergent is a substance added to water to improve its cleaning properties. Although water is a powerful solvent for many compounds, it will not dissolve grease and natural oils. Detergents are compounds that cause such nonpolar substances to go into solution in water. Soap is the original example, owing its action to the presence of ions formed from long-chain fatty acids ion (e.g. stearat ion, CH₃(CH₂)₁₆COO^-).

allotrope    →   alotrop

Allotropes are the elements which exist in two or more different forms in the same physical state. Allotropes generally differ in physical properties and may also differ in chemical activity.

Diamond, graphite and fullerenes are three allotropes of the element carbon. Graphite is a soft, black, slippery substance; by contrast, diamond is one of the hardest substances known. The different properties of the allotropes arise from their chemical structures. Diamonds typically crystallize in the cubic crystal system and consist of tetrahedrally bonded carbon atoms. Graphite crystallizes in the hexagonal system. In the fullerenes, the carbon atoms taking the form of a hollow sphere, ellipsoid, or tube.

In some cases, the allotropes are stable over a temperature range, with a definite transition point at which one changes into the other. For instance, tin has two allotropes: white (metallic) tin stable above 13.2 °C and grey (nonmetallic) tin stable below 13.2 °C.

The term allotropes may also be used to refer to the molecular forms of an element. Ozone is a chemically active triatomic allotrope of the element oxygen.

arginine    →   arginin

Arginine is an electrically charged amino acids with basic side chains. It is one of the least frequent amino acids. As a group the charged amino acids are important for making proteins soluble. These residues are generally located on the surface of the protein. Arginine is well designed to bind the phosphate anion, and is often found in the active centers of proteins that bind phosphorylated substrates. As a cation, arginine, as well as lysine, plays a role in maintaining the overall charge balance of a protein. Although arginine is considered an essential amino acid (it must be obtained through the diet), this is true only during the juvenile period in humans.

• Abbreviations: Arg, R
• IUPAC name: 2-amino-5-(diaminomethylideneamino)pentanoic acid
• Molecular formula: C₆H₁₄N₄O₂
• Molecular weight: 174.20 g/mol

heat transfer    →   prijenos topline

From observations and experiments it has been found that heat energy can be transferred from one position to another through three different modes: conduction, convection and radiation.

law of chemical equilibrium    →   zakon o kemijskoj ravnoteži

Law of chemical equilibrium (also called the law of mass action) states that the rate at which a substance reacts is proportional to its active mass (i.e. to its molar concentration). Thus, the velocity of a chemical reaction is proportional to the product of the concentration of the reactants.