CHEMISTRY GLOSSARY

ribonucleic acid    →   ribonukleinska kiselina

Ribonucleic acid is a complex organic compound in living cells that is concerned with protein synthesis. Plays an intermediary role in converting the information contained in DNA into proteins. RNA carries the genetic information from DNA to those parts of the cell where proteins are made. Some viruses store their genetic information as RNA not as DNA.

Ribonucleic acid is a similar molecule to DNA but with a slightly different structure.

The structural difference with DNA is that RNA contains a -OH group both at the 2' and 3' position of the ribose ring, whereas DNA (which stands, in fact, for deoxy-RNA) lacks such a hydroxy group at the 2' position of the ribose. The same bases can be attached to the ribose group in RNA as occur in DNA, with the exception that in RNA thymine does not occur, and is replaced by uracil, which has an H-group instead of a methyl group at the C-5 position of the pyrimidine. Unlike the double-stranded DNA molecule, RNA is a single-stranded molecule.

The three main functionally distinct varieties of RNA molecules are: (1) messenger RNA (mRNA) which is involved in the transmission of DNA information, (2) ribosomal RNa (rRNA) which makes up the physical machinery of the synthetic process, and (3) transfer RNA (tRNA) which also constitutes another functional part of the machinery of protein synthesis.

simple cubic lattice    →   jednostavna kubična rešetka

Simple or primitive cubic lattice (sc or cubic-P) has one lattice point at the each corner of the unit cell. It has unit cell vectors a = b = c and interaxial angels α=β=γ=90°.

The simplest crystal structures are those in which there is only a single atom at each lattice point. In the sc structures the spheres fill 52 % of the volume. The number of atoms in a unit cell is one (8×1/8 = 1). This is only one metal (α-polonium) that have the sc lattice.

valence    →   valencija

Valence is the charge on an ion based on the number of electrons transferred or shared within a specific structure. For example, in H₂O, oxygen has a valence of 2, carbon in CH₄ has a valence of four.

vitamin    →   vitamin

The name vitamin is obtained from vital amines as it was originally thought that these substances were all amines. This is now known not to be true as vitamins have a range of structures. The body requires a small amout of vitamins, but any deficiency leads to metabolic and physical disorders.

tautomerism    →   tautomerija

Tautomerism refers to equilibrium between two different structures of the same compound. Usually the tautomers differ in the point of attachment of a hydrogen atom. One of the most common examples of a tautomeric system is the equilibrium between a ketone (keto) and aldehyde (enol).

thermosetting plastic    →   termostabilna plastika

Thermosetting plastics (thermosets) refer to a range of polymer materials that cure, through the addition of energy, to a stronger form. The energy may be in the form of heat (rubber), through a chemical reaction (two part epoxy), or irradiation. Thermoset materials are usually liquid or malleable prior to curing, and designed to be molded into their final form, or used as adhesive.

Thermoset polymer resins transformed into plastics or rubbers by cross-linking into a rigid, 3-D structure. A thermoset material cannot be melted and re-molded after it is cured.

tryptophan    →   triptofan

Tryptophan is hydrophobic amino acids with aromatic side chain. Tryptophan is large aromatic residue that is normally found buried in the interior of a protein and is important for protein stability. Tryptophan has the largest side chain and is the least common amino acid in proteins. It has spectral properties that make it the best inherent probe for following protein folding and conformational changes associated with biochemical processes. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested.

• Abbreviations: Trp, W
• IUPAC name: 2-amino-3-(1H-indol-3-yl)propanoic acid
• Molecular formula: C₁₁H₁₂N₂O₂
• Molecular weight: 204.23 g/mol

X-ray diffraction pattern    →   rendgenski difrakcijski uzorci

X-ray diffraction pattern is an interference pattern created by x-rays as they pass through a solid material. Studying X-ray diffraction patterns gives detailed information on the three-dimensional structure of crystals, surfaces, and atoms.

valine    →   valin

Valine is hydrophobic amino acids with aliphatic side chain. It is a member of the branched-chain amino acid family, along with leucine and isoleucine. Valine differs from threonine by replacement of the hydroxyl group with a methyl substituent, but they are of roughly the same shape and volume. The nonpolar hydrophobic amino acids tend to cluster together within proteins, stabilizing protein structure by means of hydrophobic interactions. Valine is an essential amino acid, which means that it cannot be synthesized in the body and must be obtained through dietary sources.

• Abbreviations: Val, V
• IUPAC name: 2-amino-3-methylbutanoic acid
• Molecular formula: C₅H₁₁NO₂
• Molecular weight: 117.15 g/mol

volumetric pipette    →   prijenosna pipeta

Volumetric pipettes (transfer or belly pipette) are used in volumetric analysis, when there is a need for taking exact smaller volume of a sample solution or reagent. The upper tube of volumetric pipette has a ringlike marking (mark) which marks its calibrated volume. Pipettes calibrated to deliver (TD or Ex) the indicated volume. By sucking in (with mouth, propipette or a water pump) the liquid is pulled in a little bit above the mark and the opening of the pipet is closed with a forefingertip. Outer wall of pipet is wiped and, with a slight forefinger loosening, the liquid is released until it reaches the mark. Mark must figure as a tangent on a lower edge of the liquid meniscus. A pipette is emptied out by lifting the forefinger off and letting the liquid flow out of the pipette freely. After another 15 s and the tip of the pipette is pulled onto the inner wall of the vessel. It is absolutely forbidden to blow out the contents of the pipette.