CHEMISTRY GLOSSARY

critical point    →   kritična točka

In general, critical point is the point on the phase diagram of a two-phase system at which the two coexisting phases have identical properties and therefore represent a single phase. At the liquid-gas critical point of a pure substance, the distinction between liquid and gas vanishes, and the vapour pressure curve ends. The coordinates of this point are called the critical temperature and critical pressure. Above the critical temperature it is not possible to liquefy the substance.

cysteine    →   cistein

Cysteine is neutral amino acids with polar side chains. Because of its high reactivity, the thiol group of cysteine has numerous biological functions. It serves as a potent nucleophile and metal ligand (particularly for iron and zinc), but is best known for its ability to form disulfide bonds, which often make an important contribution to the stability of extracellular proteins. Cysteine is a non-essential amino acid, which means that it is biosynthesized in humans.

• Abbreviations: Cys, C
• IUPAC name: 2-amino-3-sulfanylpropanoic acid
• Molecular formula: C₃H₇NO₂S
• Molecular weight: 121.16 g/mol

Dalton’s atomic theory    →   Daltonova atomska teorija

Dalton’s atomic theory is a theory of chemical combination, first stated by John Dalton in 1803. It involves the following postulates:

1. Elements consist of indivisible small particles (atoms).

2. All atoms of the same element are identical; different elements have different types of atom.

3. Atoms can neither be created nor destroyed.

4. ’Compound elements’ (i.e. compounds) are formed when atoms of different elements join in simple ratios to form ’compound atoms’ (i.e. molecules).

Dalton also proposed symbols for atoms of different elements (later replaced by the present notation using letters).

isotropic crystal    →   izotropni kristal

The measured properties of an isotropic crystal are independent of the axis of testing. Opposite of anisotropic.

isotropy    →   izotropija

Isotropy is the property of molecules and materials of having identical physical properties in all directions.

lipophility    →   lipofilnost

Lipophility is an affinity for fats, oils or other lipids.

mineral water    →   mineralna voda

Mineral water is a groundwater that rises to the surface through a natural opening in the earth or rock and contains a relatively high concentration of mineral ions and trace of elements which can be radioactive or thermal.

mixture    →   smjesa

Mixture is a heterogeneous association of substances where various individual substances retain their identities and can usually be separated by mechanical means. Includes solutions or compounds but does not include alloys or amalgams.

deoxyribonucleic acid    →   dezoksiribonukleinska kiselina

Deoxyribonucleic acid (DNA) is a nucleic acid with 2-deoxy-D-ribose as the sugar in its nucleotides. DNA contains encoded genetic information, specifically templates for the synthesis of all of an organism’s proteins and enzymes.

DNA was first identified in the 1869 by Swiss chemist Friedrich Miescher (1844-1895). In 1953, American biologist James Dewey Watson (1928-) and English physicist Francis Harry Compton Crick (1916–2004) had discovered that DNA occurs in the cell as a double helix, with two long strands of the molecule wound around each other, and further that the chemical structure of the molecule dictates that adenine (A) always aligns or pairs with thymine (T), and cytosine (C) always pairs with guanine (G). It is this base pairing that allows DNA in a cell to copy itself, and transfer its information to a new cell. The diameter of the helix is 2.0 nm and there is a residue on each chain every 0.34 nm in the z direction. The angle between each residue on the same strand is 36°, so that the structure repeats after 10 residues (3.4 nm) on each strand.

diastereoisomer    →   dijastereoizomer

Diastereoisomers (diastereomers) are stereoisomers of a compound having two or more chiral centers that are not a mirror image of another stereoisomer of the same compound. For example, in the structure below, 1 and 2 are enantiomers and so are 3 and 4; 1 and 3 are diastereoisomers, as are 2 and 4. Unlike enantiomers, diastereoisomers need not have closely similar physical and chemical properties