CHEMISTRY GLOSSARY

coenzyme a    →   koenzim a

Coenzyme A (CoA) is an essential metabolic cofactor synthesized from cysteine, pantothenate (vitamin B5), and ATP. CoA plays important roles in many metabolic pathways, including the tricarboxylic acid (TCA) cycle, and the synthesis and oxidation of fatty acids. One of the main functions of CoA is the carrying and transfer of acyl groups. Acylated derivatives (acetyl-CoA) are critical intermediates in many metabolic reactions.

hemiacetal    →   poluacetal

Hemiacetals are organic compounds having the general formula R₂C(OH)OR’ (R’ ≠ H), derived from aldehydes or ketones by formal addition of an alcohol to the carbonyl group. Hemiacetals are generally unstable compounds. In some cases however, stable cyclic hemiacetals can be readily formed, especially when 5- and 6-membered rings are possible. In this case an intramolecular OH group reacts with the carbonyl group. Glucose and many other aldoses exist as cyclic hemiacetals whereas fructose and similar ketoses exist as cyclic hemiketals. Originally, the term was confined to derivatives of aldehydes (one R = H), but it now applies equally to derivatives of ketones (neither R = H).

nucleotide    →   nukleotid

Nucleotides are the components that made up nucleic acids. They have three major components: the first component is a nitrogenous base, which is derivative of one of two parent compounds, pyrimidine or purine; the second is a pentose, or five carbon sugar group; the third is a unit of phosphate. Each group of three nucleotides in a gene is known as a codon. Whenever the phosphate group is not present, a nucleotide becomes a nucleoside.

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.

potentiometric titration    →   potenciometrijska titracija

Potentiometric titration is a volumetric method in which the potential between two electrodes is measured (referent and indicator electrode) as a function of the added reagent volume. Types of potentiometric titrations for the determination of analytes in photoprocessing solutions include acid-base, redox, precipitation, and complexometric.

Potentiometric titrations are preferred to manual titrations, since they are more accurate and precise. They are also more easily adapted to automation, where automated titration systems can process larger volumes of samples with minimal analyst involvement.

A titration curve has a characteristic sigmoid curve. The part of the curve that has the maximum change marks the equivalence point of the titration. The first derivative, ΔE/ΔV, is the slope of the curve, and the endpoint occurs at the volume, V', where ΔE/ΔV has the maximum value.

titration curve    →   titracijska krivulja

Titration curve is a graphic representation of the amount of a species present vs. volume of solution added during a titration. A titration curve has a characteristic sigmoid curve. The inflection point in the titration curve marks the end-point of the titration. Blue line is the first derivative of the titration curve.