CHEMISTRY GLOSSARY

nuclear magnetic resonance    →   nuklearna magnetska rezonancija

Nuclear magnetic resonance (NMR) is a type of radio-frequency spectroscopy based on the magnetic field generated by the spinning of electrically charged atomic nuclei. This nuclear magnetic field is caused to interact with a very large (1 T - 5 T) magnetic field of the instrument magnet. NMR techniques have been applied to studies of electron densities and chemical bonding and have become a fundamental research tool for structure determinations in organic chemistry.

nucleic acid    →   nukleinska kiselina

Nucleic acids are a complex, high-molecular-weight biochemical macromolecules composed of nucleotide chains that convey genetic information. The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Each nucleic acid chain is composed of subunits called nucleotides, each containing a sugar, a phosphate group, and nitrogenous base. DNA was first discovered in 1869 by the Swiss biochemist Friedrich Miescher (1844-1895).

Both DNA and RNA contain the two major purine bases adenine (A) and guanine (G) and one of the major pyrimidines, cytosine (C). Of the other two pyrimidines, thymine (T) is found in DNA and uracil (U) is found in RNA. There are two major pentoses in nucleic acids:2'-deoxy-D-ribose in DNA and D-ribose in RNA.

Nucleotides are linked together in both DNA and RNA in a polymeric fashion via covalent bonds. These bonds exist through phosphate-group bridges in which the 5' hydroxyl group of one nucleotide unit is joined to the 3' hydroxyl group of the next nucleotide. RNA is usually a single-stranded molecule, whereas DNA is usually double-stranded.

octahedral molecular geometry    →   oktaedarska geometrija molekule

Octahedral molecular geometry (square bipyramidal shape) describes the shape of compounds where six atoms or ligands are symmetrically arranged around a central atom. The sulfur hexafluoride (SF₆), with six bonding pairs, is predicted and found to be a regular octahedron. Four of the attachments are positioned in a square plane with 90° bond angles. The remaining two attachments are positioned perpendicular (90°) to the square plane at opposite ends of the central atom. Molecules with an octahedral electron pair geometries have sp³d² (or d²sp³) hybridization at the central atom.

omega-3 fatty acids    →   omega-3 masne kiseline

Omega-3 fatty acids are polyunsaturated fatty acids, meaning they contain more than one double bond. The name omega-3 indicates that the first double bond occurs on the third carbon atom (n-3) from the methyl (-CH₃) end of the molecule (omega position). The three main omega-3 fatty acids are alpha-linolenic acid (ALA, 18:3n-3), eicosapentaenoic acid (EPA, 20:5n-3), and docosahexaenoic acid (DHA, 22:6n-3). ALA comes from plants. EPA and DHA come from fish.

Similarly, the first double bond in omega-6 fatty acids is located between the sixth and seventh carbon atom (n-6) from the methyl end of the fatty acid (omega end).

Onsager relations    →   Onsagerove relacije

Onsager relations are an important set of equations in the thermodynamics of irreversible processes. They express the symmetry between the transport coefficients describing reciprocal processes in systems with a linear dependence of flux (J_i) on driving forces (X_j).

In Onsager’s theory the coupling coefficients are equal, L_ij = L_ji. This is known as reciprocal relations. The theory was developed by the Norwegian chemist Lars Onsager (1903-1976) in 1931.

peptide    →   peptid

Peptides are amides derived from two or more amino acids (the same or different) linked by peptide bonds. These bonds are formed by the reaction between adjacent carboxyl (-COOH) and amino (-NH₂) groups with the elimination of water.

polypeptide    →   polipeptid

Polypeptides are peptides containing ten or more amino acid residues. The properties of a polypeptide are determined by the type and sequence of its constituent amino acids.

polysaccharide    →   polisaharid

Polysaccharides are compounds consisting of a large number of simple sugars (monosaccharides) linked together by glycosidic bonds. When polysaccharides are composed of a single monosaccharide building block, they are termed homopolysaccharides. Heteropolysaccharides contain two or more different types of monosaccharide. Polysaccharides may have molecular weights of up to several million and are often highly branched. Since they have only the one free anomeric -OH group at the end of a very long chain, polysaccharides aren’t reducing sugars and don’t show noticeable mutarotation. The most common polysaccharides are cellulose, starch, and glycogen.

semiconductor    →   poluvodič

Semiconductor is a material in which the highest occupied energy band (valence band) is completely filled with electrons at T = 0 K, and the energy gap to the next highest band (conduction band) ranges from 0 to 4 or 5 eV. With increasing temperature electrons are excited into the conduction band, leading to an increase in the electrical conductivity.

serine    →   serin

Serine is neutral amino acids with polar side chains. It is one of two hydroxyl amino acids. Both are commonly considered to by hydrophilic due to the hydrogen bonding capacity of the hydroxyl group. Serine often serves as a nucleophile in many enzyme active sites, and is best known for its role in the serine proteases. Serine is a site of phosphorylation and glycosylation which is important for enzyme regulation and cell signaling. It is not essential to the human diet, since it is synthesized in the body from other metabolites, including glycine.

• Abbreviations: Ser, S
• IUPAC name: 2-amino-3-hydroxypropanoic acid
• Molecular formula: C₃H₇NO₃
• Molecular weight: 105.09 g/mol