CHEMISTRY GLOSSARY

valence bond theory    →   teorija valentne veze

Valence bond theory is a theory that explains the shapes of molecules in terms of overlaps between half-filled atomic orbitals, or half filled hybridised orbitals.

VSEPR    →   VSEPR

Valence shell electron pair repulsion theory (VSEPR) is a model that explains the shapes of molecules by assuming that electron pairs arrange themselves around atoms in a way that minimizes electron-electron repulsions.

liquid aggregate state    →   tekuće agregatno stanje

Liquids have a constant volume, but they do not have a constant shape. They assume the shape of a vessel they are in at the moment. It happens because molecules of liquids are still close enough to each other, the attracting forces still being very strong.

lysine    →   lizin

Lysine is an electrically charged amino acids with basic side chains. Lysine is a base, as are arginine and histidine. The amino group is highly reactive and often participates in reactions at the active centers of enzymes. Lysine plays an important role in coordinating negatively charged ligands. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested.

• Abbreviations: Lys, K
• IUPAC name: 2,6-diaminohexanoic acid
• Molecular formula: C₆H₁₄N₂O₂
• Molecular weight: 146.19 g/mol

macromolecule    →   makromolekule

Macromolecule is a molecule of high relative molecular mass (molecular weight), the structure of which essentially comprises the multiple repetitions of units derived, actually or conceptually, from molecules of low relative molecular mass. The types of macromolecules are natural and synthetic polymers, carbohydrates, lipids, proteins etc. Cellulose is a polysaccharide that is made up of hundreds, even thousands of glucose molecules strung together.

metallic glass    →   metalno staklo

Certain alloys can solidify by extremely rapid cooling out of melt without formation of a crystal lattice, that is in the amorphous form - such, amorphous alloys are so called metallic glasses. The alloy of zirconium, beryllium, titanium, copper, and nickel is one of the first metallic glasses that can be made in bulk and formed into strong, hard, useful objects.

Unlike pure metals and most metal alloys, metallic glasses have no regular crystalline structure. This lack of long range order or microstructure is related to such desirable features as strength and low damping which is one reason why the premier use for zirconium-based metallic glass is in the manufacture of expensive golf club heads. Metallic glasses can be quite strong yet highly elastic, and they can also be quite tough (resistant to fracture). Even more interesting are the thermal properties; for instance, just like an oxide glass, there is a temperature (called the glass transition temperature) above which a metallic glass becomes quite soft and flows easily. This means that there are lots of opportunities for easily forming metallic glasses into complex shapes.

methionine    →   metionin

Methionine is neutral amino acids with polar side chains. It is one of the two sulfur-containing amino acids. Methionine is a fairly hydrophobic amino acid and typically found buried within the interior of a protein. It can form stacking interactions with the aromatic moieties of tryptophan, phenylalanine, and tyrosine. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested.

• Abbreviations: Met, M
• IUPAC name: 2-amino-4-methylsulfanylbutanoic acid
• Molecular formula: C₅H₁₁NO₂S
• Molecular weight: 149.21 g/mol

molar mass    →   molarna masa

Molar mass is the mass of one mole of a substance.

It is normally expressed in units of g mol^-1, in which case its numerical value is identical with the relative molecular mass.

monosaccharide    →   monosaharid

Monosaccharides are carbohydrates, with the general formula C_n(H₂O)_n, that cannot be decomposed to a simpler carbohydrates by hydrolysis.

Depending on whether the molecule contains an aldehyde group (-CHO) or a ketone group (-CO-) monosaccharide can be a polyhydroxy aldehyde (aldose) or a polyhydroxy ketone (ketose). These aldehyde and ketone groups confer reduction properties on monosaccharides. They are also classified according to the number of carbon atoms they contain: trioses have three carbon atoms, tetroses four, pentoses five, hexoses six, heptoses seven, etc. These two systems of classification are often combined. For example, a six-carbon polyhydroxy aldehyde such as D-glucose is an aldohexose, whereas a six-carbon polyhydroxy ketone such as D-fructose is a ketohexose.

The notations D and L are used to describe the configurations of carbohydrates. In Fischer projections of monosaccharides, the carbonyl group is always placed on top (in the case of aldoses) or as close to the top as possible (in the case of ketoses). If the OH group attached to the bottom-most asymmetric carbon (the carbon that is second from the bottom) is on the right, then the compound is a D-sugar. If the OH group is on the left, then the compound is an L-sugar. Almost all sugars found in nature are D-sugars.

Monosaccharides can exist as either straight-chain or ring-shaped molecules. During the conversion from straight-chain form to cyclic form, the carbon atom containing the carbonyl oxygen, called the anomeric carbon, becomes a chiral center with two possible configurations (anomers), α and β. When the stereochemistry of the first carbon matches the stereochemistry of the last stereogenic center the sugar is the α-anomer when they are opposite the sugar is the β-anomer.

Nernst’s division law    →   Nernstov zakon razdjeljenja

Nernst’s division law states that a substance is divided between two solvents in a way that proportion of concentrations of that substance is at certain temperatures constant, under the condition that both solvents are in the same molecular state. Division coefficient is a proportion of substance concentration in solvents A i B at a defined temperature.

Appearance of division is used for substance extraction.