CHEMISTRY GLOSSARY

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.

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.

orbital    →   orbitala

Orbital is the area in space about an atom or molecule in which the probability of finding an electron is greatest.

The possible atomic orbitals correspond to subshells of the atom. Thus there is one s-orbital for each shell (orbital quantum number l = 0). There are three p-orbitals (corresponding to the three values of l) and five d-orbitals. The shapes of orbitals depend on the value of l.

phenylalanine    →   fenilalanin

Phenylalanine is hydrophobic amino acids with aromatic side chain. It is quite hydrophobic and even the free amino acid is not very soluble in water. Phenylalanine is large aromatic residue that is normally found buried in the interior of a protein and is important for protein stability. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested.

• Abbreviations: Phe, F
• IUPAC name: 2-amino-3-phenylpropanoic acid
• Molecular formula: C₉H₁₁NO₂
• Molecular weight: 165.19 g/mol

planary structure    →   planarna struktura molekule

Planary structure of molecule is a structure of molecule in which all atoms in the molecule lie in the same plane.

plastic    →   plastika

Plastic is a material that can be shaped by the application of heat or pressure. Most are based on synthetic polymers although some are the product of natural substances (such as cellulose derivatives, but excluding the rubbers.). They are usually light and permanent solids, being also heat and electric isolators. If the materials soften again when reheated, they are said to be thermoplastic. If, after fashioning, they resist further applications of heat, they are said to be thermoset.

polymer    →   polimer

Polymer is a substance composed of molecules of high relative molecular mass (molecular weight), the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass (monomers). In most cases the number of monomers is quite large and is often not precisely known. A single molecule of a polymer is called a macromolecule. Polystyrene is light solid material obtained by polymerisation of styrene (vinyl benzene).

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.

potential energy    →   potencijalna energija

Potential energy (E_p) is the energy stored in a body or system as a consequence of its position, shape, or state (this includes gravitation energy, electrical energy, nuclear energy, and chemical energy). Gravitational potential energy is the energy associated with the state of separation between bodies that attracts each other via gravitational force. Elastic potential energy is the energy associated with the state of compression or extension of an elastic object. Thermal energy is associated with the random motions of atoms and molecules in a body.

proline    →   prolin

Proline has an aliphatic side chain with a distinctive cyclic structure. It is unusual because it is conformationally restricted. The secondary amino (imino) group of proline residues is held in a rigid conformation that reduces the structural flexibility of polypeptide regions containing proline. It is not an essential amino acid, which means that the human body can synthesize it.

• Abbreviations: Pro, P
• IUPAC name: pyrrolidine-2-carboxylic acid
• Molecular formula: C₅H₉NO₂
• Molecular weight: 115.13 g/mol