CHEMISTRY GLOSSARY

lithosphere    →   litosfera

Lithosphere (from the Greek for rocky sphere) is rigid, rocky outer layer of the Earth, consisting of the crust and the solid outermost layer of the upper mantle. The distinguishing characteristic of the lithosphere is not its composition but its flow properties. It floats on the asthenosphere, which is the heat-softened layer of the mantle below the lithosphere.

The lithospheric is not one continuous piece but is broken into about a dozen major separate rigid blocks, or plates, which move independently relative to one another. This movement of lithospheric plates over the asthenosphere is described as plate tectonics. When an oceanic plate and a continental plate meet, the heavier oceanic plate (composed mostly of basalt, specific gravity about 3.0 or peridotite, specific gravity about 3.3) subducts under the lighter continental plate (composed mostly of granite, specific gravity about 2.7).

living planet index    →   indeks života na planetu

The Living Planet Index (LPI) reflects changes in the health of the planet's ecosystems by tracking trends in nearly 8000 populations of vertebrate species. The LPI first calculates the annual rate of change for each species population in the dataset, then calculates the average change across all populations for each year from 1970, when data collection began, to 2007, the latest date for which data is available.

The Global LPI shows a decline of around 30 % from 1970 to 2007, based on 7953 populations of 2544 species of birds, mammals, amphibians, reptiles and fish.

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

metal    →   metal

Metals are materials in which the highest occupied energy band (conduction band) is only partially filled with electrons.

Their physical properties generally include:

- They are good conductors of heat and electricity. The electrical conductivity of metals generally decreases with temperature.

- They are malleable and ductile in their solid state.

- They show metallic lustre.

- They are opaque.

- They have high density.

- They are solids (except mercury)

- They have a crystal structure in which each atom is surrounded by eight to twelve near neighbours

Their chemical properties generally are:

- They have one to four valence electrons.

- They have low ionisation potentials; they readily lose electrons.

- They are good reducing agents.

- They have hydroxides which are bases or amphoteric.

- They are electropositive.

Metallic characteristics of the elements decrease and non-metallic characteristics increase with the increase of valence electrons. Also metallic characteristics increase with the number of electron shells. Therefore, there is no sharp dividing line between the metals and non-metals.

Of the 114 elements now known, only 17 show primarily non-metallic characteristics, 7 others are metalloids, and 89 may be classed as metals.

methyl orange    →   metil oranž

Methyl orange is an acid-base indicator, in acid it turns red and in a base it turns yellow.

metre    →   metar

Metre (m) is the SI base unit of length.

The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 s.

This definition, adopted by the General Conference on Weights and Measure in October 1983, replaced the 1967 definition based on the krypton lamp.

Moh’s scale    →   Mohsova skala

Mohs’ scale of mineral hardness characterises the scratch resistance of various minerals through the ability of a harder material to scratch a softer. It was created by the German mineralogist Friedrich Mohs (1773-1839). Mohs based the scale on the ten readily available minerals.

mole    →   mol

Mole (mol) is the SI base unit of amount of substance.

The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kg of carbon 12.

When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles. In this definition, it is understood that the carbon 12 atoms are unbound, at rest and in their ground state.

nuclear magnetic resonance    →   nuklearna magnetska rezonancija

Nuclear magnetic resonance (NMR) is a type of radio-frequency spectroscopy based on the magnetic field generated by the spinning of electrically charged atomic nuclei. This nuclear magnetic field is caused to interact with a very large (1 T - 5 T) magnetic field of the instrument magnet. NMR techniques have been applied to studies of electron densities and chemical bonding and have become a fundamental research tool for structure determinations in organic chemistry.

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.