CHEMISTRY GLOSSARY

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.

porphyrin    →   porfirin

Porphyrin is a planar ligand with a central ring structure and various substituent groups at the edges of the ring.

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

retardation factor    →   faktor zaostajanja

Retardation factor, R_F, (in planar chromatography) is a ratio of the distance travelled by the centre of the spot to the distance simultaneously travelled by the mobile phase:

The R_F value is characteristic for any given compound on the same stationary phase using the same mobile phase for development of the plates. Hence, known R_F values can be compared to those of unknown substances to aid in their identifications.

second-order reactions    →   reakcije drugog reda

Second-order reaction is a reaction with a rate law that is proportional to either the concentration of a reactant squared, or the product of concentrations of two reactants.

For a general unimolecular reaction,

The reaction rate expression for a second order reaction is

If assumed that the concentration of reactant A is [A]_o at t=0 and [A] at time T, the variables in the rate equation and integrate can be separated. The integrated rate law for a second-order reaction can be easily shown to be

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

standard    →   standard

Standards are materials containing a known concentration of an analyte. They provide a reference to determine unknown concentrations or to calibrate analytical instruments.

The accuracy of an analytical measurement is how close a result comes to the true value. Determining the accuracy of a measurement usually requires calibration of the analytical method with a known standard. This is often done with standards of several concentrations to make a calibration or working curve.

A primary standard is a reagent that is extremely pure, stable, has no waters of hydration, and has a high molecular weight.

A secondary standard is a standard that is prepared in the laboratory for a specific analysis. It is usually standardised against a primary standard.

stereoisomer    →   stereoizomer

Stereoisomers are compounds that have identical chemical constitution, but differ as regards the arrangement of the atoms or groups in space. Stereoisomers fall into two broad classes: optical isomers (enantiomers) and geometric isomers (cis-trans).

sugar    →   šećer

Sugar is any of a group of water-soluble carbohydrates of relatively low molecular weight and typically having a sweet taste. The group comprises mainly monosaccharides (glucose, fructose, galactose), disaccharides (sucrose, lactose, maltose), and trisaccharides (raffinose). Many monosaccharides and disaccharides fairly commonly found in nature bear names reflecting the source from which they were first isolated. For example, glucose is also known as grape sugar, lactose as milk sugar, and maltose as malt sugar. In everyday usage, the name is often used to refer specifically to sucrose (table sugar, cane sugar, beet sugar).

threonine    →   treonin

Threonine is neutral amino acids with polar side chains. It differs from serine by having a methyl substituent in place of one of the hydrogens on the β carbon. Threonine is a site of phosphorylation and glycosylation which is important for enzyme regulation and cell signaling. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested.

• Abbreviations: Thr, T
• IUPAC name: 2-amino-3-hydroxybutanoic acid
• Molecular formula: C₄H₉NO₃
• Molecular weight: 119.12 g/mol