The Limits of Organic Life in Planetary Systems (2007) / Chapter Skim
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Appendix A Glossary
Appendix A Glossary
Pages 89-96
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Appendixes
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group; there are 20 a-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)
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Catalyst A substance that enhances the rate of reaction by providing a lower-energy alternative pathway Chemolithoautotroph An organism capable of generating metabolically useful energy by the oxida tion of inorganic compounds Chirality Handedness; property of a molecule configured such that it cannot be super imposed on its mirror image Chondrite A stony meteorite that contains spherical bodies of pyroxene and olivine minerals Codon The basic unit of the genetic code; a set of any three adjacent bases in DNA or RNA A natural white or colorless hydrated calcium borate, Ca2B6O11D 2O Colemanite 5H Cosmic rays High-energy charged particles consisting of atomic nuclei, electrons, and pro tons and originating from the Sun and from energetic astrophysical processes (e.g., those associated with black holes, supernovas, and so on) Cryosolvent A solvent for maintaining constant low temperature Cryptoendolith An organism that lives within rocks on Earth's surface Cytotoxic Producing toxic effects on cells
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Gray (Gy) Unit of absorbed dose of ionizing radiation corresponding to the absorption of 1 J per kg of absorbing material; 1 gray 5 100 rads; on Earth a typical mid latitude, sea-level natural background level is 0.3 mGy per year, whereas on the surface of Europa the level is almost 1010 times higher, enough to kill humans in one minute of exposure)
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into simpler compounds with the exchange of energy Metallicity A measure of the proportion of an object's matter that is made up of chemical elements other than hydrogen and helium Methanogen An organism capable of producing methane from the decomposition of organic material Monomer A building block of a polymer, including a biopolymer; amino acids are monomers of polypeptides (proteins) , and nucleotides are monomers of nucleic acids Murchison (meteorite)
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and hydrogen; are flat, with each carbon having three neighboring atoms, much like graphite; and are a standard product of combustion Polyelectrolyte An electrolyte, such as a protein or polysaccharide, that has a high molecular weight Polysaccharides A class of high-molecular-weight carbohydrates that can be broken down to monosaccharides on hydrolysis Prebiotic Occurring before life appeared on Earth Protein Any of a group of complex organic compounds, consisting essentially of com
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THE LIMITS OF ORGANIC LIFE IN PLANETARY SYSTEMS binations of amino acids in peptide linkages, that contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur Protonated Having protons added to a base Protoplanetary disk The disk of dust and gas surrounding a star out of which planets form Psychrophilic Requiring low temperatures for growth Radiolysis The breakdown of molecules as a result of exposure to ionizing radiation Retrotransposon A transposon copied from RNA with the use of reverse transcriptase Ribosome A minute, round particle composed of RNA and protein found in the cytoplasm of living cells and active in the synthesis of proteins RNA Ribonucleic acid rRNA Ribosomal RNA Serpentinization reaction A hydrothermal reaction by which magnesium-rich silicate minerals are con verted into or replaced by serpentine minerals Siderophore A molecular receptor that binds and transports iron Silane Any of a group of silicon hydrides having the general formula SiH that are analogous to the paraffin hydrocarbons Sphalerite The primary ore of zinc, occurring in usually yellow-brown or brownish-black crystals or cleavage masses, essentially ZnS with some cadmium, iron, and manganese Stereochemistry The branch of chemistry concerned with the study of how atoms or molecules are affected by their three-dimensional spatial arrangement, e.g., the study of stereoisomers Synthetic biology Engineering of biological components or systems that are not known to nature or the reengineering of existing biological components Tagish Lake (meteorite) A unique carbonaceous chondrite collected very soon after falling to Earth in a remote part of northwestern Canada in January 2001 Thermophile An organism adapted to living in high-temperature environments Thioester Compound resulting from the bonding of sulfur with an acyl group with the general formula R-S-CO-R Tholin A term used in planetary science to refer generally to organic heteropolymers; the reddish tar-like organic residue created in simulations of the action of ultraviolet radiation on gases typically found in planetary environments Thymidine A nucleoside, C10H14N2O5, composed of thymine and deoxyribose Vesicle A microscopic volume defined by a boundary structure; examples include self assembled vesicles bounded by a membranous lipid bilayer, and small cavities formed in volcanic rock by entrapment of a gas bubble during solidification Vitrification The process of liquid water moving directly into the glassy state without ice crystal formation
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