Abiotic Of or relating to nonliving things; independent of life or living organisms

Acidophile An organism adapted to living in highly acidic environments

ADP Adenosine diphosphate

Aerosol A fine aerial suspension of liquid (mist, fog) or solid (dust, fume, smoke) particles

Albedo The fraction of light that is reflected by a surface; commonly used in astronomy to describe the reflective properties of planets, satellites, and asteroids

Alkalophile An organism that is adapted to living in highly alkaline environments

Amino acid Any organic compound containing an amino (NH2) and a carboxyl (COOH) group; there are 20 α-amino acids from which proteins are synthesized during ribosomal translation of mRNA

Anaerobe An organism that lives and reproduces in the absence of dissolved oxygen, instead using oxidants such as iron and sulfur compounds in energy metabolism

Anoxic Lacking oxygen

Aquaporin A water channel that form pores in the membranes of cells and selectively conducts water molecules through the membrane, while preventing the passage of ions (such as sodium and potassium) and other small molecules

Archaea (Archaebacteria) A group of unique microorganisms classified as bacteria that are related only distantly to eukaryotes and other prokaryotes

Aromatic hydrocarbon A member of the class of hydrocarbons consisting of assemblages of cyclic conjugated carbon atoms and characterized by large resonance energies

Asteroid A small, rocky body in orbit around the Sun, found mainly between the orbits of Mars and Jupiter

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