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| 488518946 | alternative splicing | Splicing of RNA transcripts from the same gene in different ways, each of which produces a distinct protein. | 0 | |
| 488518947 | aminoacyl-tRNA synthetase | Enzyme that attaches the correct amino acid to a tRNA molecule to form an aminoacyl-tRNA. | 1 | |
| 488518948 | anticodon | Sequence of three nucleotides in a transfer RNA molecule that is complementary to the three-nucleotide codon on a messenger RNA molecule; each anticodon is matched to a specific amino acid covalently attached elsewhere on the transfer RNA molecule. | 2 | |
| 488518949 | codon | Sequence of three nucleotides in a DNA or messenger RNA molecule that represents the instruction for incorporation of a specific amino acid into a growing polypeptide chain. | 3 | |
| 488518950 | exon | Segment of a eucaryotic gene that is transcribed into RNA and expressed; dictates the amino acid sequence of part of a protein. | 4 | |
| 488518951 | gene expression | The process by which a gene makes its effect on a cell or organism by directing the synthesis of a protein or an RNA molecule with a characteristic activity. | 5 | |
| 488518952 | genetic code | Set of rules specifying the correspondence between nucleotide triplets (codons) in DNA or RNA and amino acids in proteins. | 6 | |
| 488518953 | general transcription factors | Proteins that assemble on the promoters of many eucaryotic genes near the start site of transcription and load the RNA polymerase in the correct position. | 7 | |
| 488518954 | initiator tRNA | Special tRNA that initiates translation. It always carries the amino acid and methionine. | 8 | |
| 488518955 | intron | Noncoding region of a eucaryotic gene that is transcribed into an RNA molecule but is then excised by RNA splicing to produce mRNA. | 9 | |
| 488518956 | messenger RNA (mRNA) | RNA molecule that specifies the amino acid sequence of a protein. Produced by RNA splicing (in eucaryotes) from a large RNA molecule made by RNA polymerase as a complementary copy of DNA. It is translated into protein in a process catalyzed by ribosomes. | 10 | |
| 488518957 | promotor | Nucleotide sequence in DNA to which RNA polymerase binds to begin transcription. | 11 | |
| 488518958 | protease | Enzyme such as trypsin that degrades proteins by hydrolyzing some of their peptide bonds. | 12 | |
| 488518959 | proteasome | Large protein complex in the cytosol that is responsible for degrading cytosolic proteins that have been marked for destruction by ubiquiylation or by some other means. | 13 | |
| 488518960 | reading frame | The set of successive triplets in which a string of nucleotides is translated into protein. An mRNA molecule is read in one of three possible reading frames, depending on the starting point. | 14 | |
| 488518961 | ribosomal RNA (rRNA) | Any one of a number of specific RNA molecules that form part of the structure of a ribosome and participate in the synthesis of proteins. Often distinguished by their sedimentation coefficient. | 15 | |
| 488518962 | ribosome | Particle composed of ribosomal RNAs and ribosomal proteins that associates with messenger RNA and catalyzes the synthesis of protein. | 16 | |
| 488518963 | ribozyme | An RNA molecule possessing catalytic properties. | 17 | |
| 488518964 | RNA polymerase | Enzyme that catalyzes the synthesis of an RNA molecule on a DNA template from nucleoside triphosphate precursors. | 18 | |
| 488518965 | RNA processing | The modifications that an RNA undergoes as it reaches its mature form. For a eucaryotic mRNA, processing typically includes capping, splicing, and polyadenylation. | 19 | |
| 488518966 | RNA splicing | Process to which intron sequences are excised from RNA molecules in the nucleus during the formation of messenger RNA. | 20 | |
| 488518967 | small nuclear RNA (snRNA) | RNA molecules of around 200 nucleotides involved in RNA splicing. | 21 | |
| 488518968 | spliceosome | Large assembly of RNA and protein molecules that splices introns out of pre-mRNA in eucaryotic cells. | 22 | |
| 488518969 | transcription | A process that uses one strand of DNA as the template to synthesize a complementary RNA sequence, sometimes termed the primary transcript, catalyzed by the enzyme RNA polymerase. | 23 | |
| 488518970 | transfer RNA (tRNA) | Set of small RNA molecules used in protein synthesis as an interface (adaptor) between mRNA and amino acids. Each type of tRNA molecule is covalently linked to a particular amino acid. | 24 | |
| 488518971 | translation | Process by which the sequence of nucleotides in a messenger RNA molecule directs the incorporation of amino acids into protein; occurs on a ribosome. | 25 | |
| 488518972 | translation initiation factor | Protein that promotes the proper association of ribosomes with mRNA and is required for the initiation of protein synthesis. | 26 | |
| 488518973 | DNA polymerase | Enzyme that catalyzes the addition of nucleotide subunits to make DNA. | 27 | |
| 488518974 | DNA repair | Collective term for the enzymatic processes that correct deleterious changes affecting the continuity or sequence of a DNA molecule | 28 | |
| 488518975 | DNA replication | The process by which a copy of a DNA molecule is made. | 29 | |
| 488518976 | homologous recombination | Genetic exchange between a pair of identical or very similar DNA sequences, typically located on a pair of homologous chromosomes. A similar process is used to repair double-stranded breaks in DNA. | 30 | |
| 488518977 | lagging strand | One of the two newly made strands of DNA found at a replication fork. The lagging strand is made in discontinuous lengths that are later joined covalently. | 31 | |
| 488518978 | leading strand | One of two newly made strands of DNA found as a replication fork. The leading strand is made by continuous synthesis in the 5'-to-3' direction. | 32 | |
| 488518979 | mobile genetic element | Short segment of DNA that can move, sometimes through an RNA intermediate, from one location in a genome to another. They are an important source of genetic variation in most genomes. | 33 | |
| 488518980 | mutation | A randomly produced, heritable change in the nucleotide sequence of a chromosome. | 34 | |
| 488518981 | nonhomologous end-joining | Mechanism for repairing double-strand breaks in DNA in which the two broken ends are brought together and rejoined without requiring sequence homology. | 35 | |
| 488518982 | Okazaki fragment | Short length of DNA produced on the lagging strand during DNA replication. Adjacent fragments are rapidly joined together by DNA ligase to form a continuous DNA strand. | 36 | |
| 488518983 | proofreading | The process by which DNA polymerase corrects its own errors as it moves along DNA. | 37 | |
| 488518984 | replication fork | Y-shaped region of a replicating DNA molecule at which the two daughter strands are formed and seperate. | 38 | |
| 488518985 | retrotransposon | Type of mobile genetic element that moves by being first transcribed into an RNA copy that is reconverted to DNA by reverse transcriptase and inserted elsewhere in the chromosomes. | 39 | |
| 488518986 | retrovirus | RNA-containing virus that replicates in a cell by first making a double-stranded DNA intermediate. This DNA is inserted into the cell's chromosome, where it can be maintained for a long time and its transcribed to produce new viral genomes and mRNAs that encode viral proteins. | 40 | |
| 488518987 | reverse transcriptase | Enzyme that makes a double-stranded DNA copy from a single-stranded RNA template molecule. Present in retroviruses and as part of the transposition machinery of retrotransposons. | 41 | |
| 488518988 | telomerase | Enzyme that elongates telomeres, the repetitive nucleotide sequences found at the ends of eucaryotic chromosomes. | 42 | |
| 488518989 | template | A molecular structure that serves as a pattern for the production of other molecules. Thus, a specific sequence of nucleotides in DNA can act as a template to direct the synthesis of a new strand of complementary DNA. | 43 | |
| 488518990 | transposon | Short segments of DNA that can move from one location to another in the genome. Also known as mobile genetic element. | 44 | |
| 488518991 | virus | Particle consisting of nucleic acid (RNA to DNA) enclosed in a protein coat and capable of replicating within a host cell and spreading from cell to cell. OFten the cause of disease. | 45 | |
| 488518992 | base pair | Two nucleotides in an RNA or DNA molecule that are specifically paired with hydrogen bonds--for example G with C, and A with T or U. | 46 | |
| 488518993 | cell cycle | Reproductive cycle of the cell: the orderly sequence of events by which a cell duplicates its contents and divides in two. | 47 | |
| 488518994 | centromere | Constricted region of a mitotic chromosome that holds sister chromatids together; also the site on the DNA where the kinetochore forms and then captures microtubules from the mitotic spindle. | 48 | |
| 488518995 | chromatin | Complex of DNA, histones, and nonhistone proteins found in the nucleus of a eucaryotic cell. The material of which chromosomes are made. | 49 | |
| 488518996 | chromatin-remodeling complex | Enzyme (typically multisubunit) that uses the energy of ATP hydrolysis to alter histone-DNA interactions in eucaryotic chromosomes; the resulting altercation changes the accessibility of the underlying DNA to other proteins, including those involved in transcription. | 50 | |
| 488518997 | chromosome | Long threadlike structure composed of DNA and associated proteins that carries the genetic information of an organism. Especially visible when plant and animal cells undergo mitosis or meiosis. | 51 | |
| 488518998 | complementary | Describes two molecular surfaces that fit together closely and form noncovalent bonds with each other. Examples include complementary base pairs, such as A and T, and two complementary strands of DNA molecule. | 52 | |
| 488518999 | double helix | The typical conformation of a DNA molecule in which two polynucleotide strands are would around each other with base pairing between the strands. | 53 | |
| 488519000 | epigenetic inheritance | Inherited that is superimposed on the information inherited in the DNA sequence itself. Often, information in the form of a particular type of chromatin structure (eg a certain pattern of histone modification or DNA methylation). | 54 | |
| 488519001 | euchromatin | One of the two main states in which chromatin exists within an interphase cell, the other being heterochromatin. Characterized by particular histone modifications and associated proteins, genes in euchromatin are in general able to be expressed. | 55 | |
| 488519002 | gene | Region of DNA that controls a discrete hereditary characteristic of an organism, usually responsible for specifying a single protein or RNA molecule. | 56 | |
| 488519003 | genome | The total genetic information carried by a cell or an organism (or the DNA molecules that carry this information). | 57 | |
| 488519004 | heterochromatin | Region of a chromosome that remains unusually condensed and transcriptionally inactive during interphase. | 58 | |
| 488519005 | histone | One of a group of abundant basic proteins, rich in arginine and lysine, that are associated with DNA in chromosomes to form nucleosomes. | 59 | |
| 488519006 | karyotype | A display of the full set of chromosomes of a cell arranged with respect to size, shape, and number. | 60 | |
| 488519007 | nucleolus | Large structure in the nucleus where ribosomal RNA is transcribed and ribosomal subunits are assembled. | 61 | |
| 488519008 | nucleosome | Beadlike structural unit of a eucaryotic chromosome composed of a short length of DNA wrapped around a core of histone proteins; the fundamental subunit of chromatin. | 62 | |
| 488519009 | replication origin | Site on a chromosome at which DNA replication begins. | 63 | |
| 488519010 | telomere | Structure at the ends of linear chromosomes, associated with a characteristic DNA sequence that is replicated in a special way. Counteracts the tendency of the chromosome otherwise to shorten with each round of replication. | 64 | |
| 488519011 | active site | Specialized region of an enzyme surface to which a substrate molecule binds before it undergoes a catalyzed reaction. | 65 | |
| 488519012 | allosteric | Describes a protein that can exist in two or more conformations depending on the binding of the molecule (a ligand) at a site other than the catalytic site. Allosteric proteins composed of multiple subunits often display a cooperative response to ligand binding, because the binding of a ligand to one subunit facilitates the binding of ligands to the other subunit. | 66 | |
| 488519013 | α helix | Common structural motif of proteins in which a linear sequence of amino acids folds into a right-handed helix stabilized by internal hydrogen bonding between backbone atoms. | 67 | |
| 488519014 | amino acid sequence | The order of amino acid residues in a protein chain. Sometimes called the primary structure of a protein. | 68 | |
| 488519015 | antibody | Protein produced by B lymphocytes in response to a foreign molecule or invading organism. Binds to the foreign molecule or cell extremely tightly, thereby inactivating it or marking it for destruction. | 69 | |
| 488519016 | antigen | Molecule that provokes the production of specific neutralizing antibodies in an immune response. | 70 | |
| 488519017 | β sheet | Folding pattern found in many proteins in which neighboring regions of the polypeptide chain associate side by side with each other through hydrogen bonds to give a rigid, flattened structure. | 71 | |
| 488519018 | binding site | Region on the surface of a protein, typically a cavity or groove, that is complementary in shape to, and forms multiple noncovalent bonds with, a second molecule (the ligand). | 72 | |
| 488519019 | chromatography | A type of technique used to separate molecules in a mixture on the basis of their size, charge, or their ability to find a particular chemical group. In a common form of the technique, the mixture is run through a column filled with a particulate matrix that is designed to bind (or let through) the desired molecule. | 73 | |
| 488519020 | coiled-coil | Especially stable rod-like protein structure formed by two or more α helices coiled around each other. | 74 | |
| 488519021 | conformation | Spatial location of the atoms of a molecule relative to each other. The precise shape of a protein or other macromolecule in three dimensions. | 75 | |
| 488519022 | disulfide bond (S-S bond) | Covalent linkage formed between two sulfhydryl groups on cysteines. Common way to join two proteins or to link together different parts of the same protein in the extracellular space. | 76 | |
| 488519023 | electrophoresis | Technique for separating mixture of proteins of DNA fragments by size and electrical charge by placing them on a polymer gel and subjecting them to an electric field. The molecules migrate through the gel at different speeds depending on their size and net charge. | 77 | |
| 488519024 | feedback inhibition | A form of metabolic control in which the end product of a chain of enzymatic reactions reduces the activity of an enzyme early in the pathway. | 78 | |
| 488519025 | fibrous protein | A protein with an elongated shape. Typically one such as collagen or intermediate filament protein that is able to associate into long filamentous structures. | 79 | |
| 488519026 | globular protein | Any protein with an approximately rounded shape. Most enzymes are globular. | 80 | |
| 488519027 | GTP-binding protein | An allosteric protein whose conformation and activity are determined by its association with either GTP or GDP. Includes many proteins involved in cell signaling, such as Ras and G proteins. | 81 | |
| 488519028 | helix | An elongated structure in which a filament or thread twists in a regular fashion around a central axis. | 82 | |
| 488519029 | ligand | A molecule that binds to a specific site on a protein. | 83 | |
| 488519030 | motor protein | Protein such as myosin or kinesin that uses energy derived from ATP hydrolysis to propel itself along a protein filament or polymeric molecule. | 84 | |
| 488519031 | nuclear magnetic resonance (NMR) spectroscopy | Technique used for determining the three-dimensional structure of a protein. It is performed in solution without requiring a protein crystal. | 85 | |
| 488519032 | polypeptide polypeptide chain | Linear polymer composed of multiple amino acids. Proteins are composed of one or more long polypeptide chains. | 86 | |
| 488519033 | polypeptide backbone | The chain of atoms containing repeating peptide bonds that runs through a protein molecule and to which the amino acid side chains are attached. | 87 | |
| 488519034 | protein domain | Small discrete region of a structure. A protein domain is a compact and stable folded region of polypeptide. A membrane domain is a region of bilayer with a characteristic lipid and protein composition. | 88 | |
| 488519035 | protein family | A group of proteins in an organism with a similar amino acid sequence. The similarity is thought to reflect the evolution of the genes that encode the proteins from a common ancestor gene through a process of gene duplication followed by gene divergence. Usually, the different members of a protein family will have related but distinct functions. For example, each member of the protein kinase family carries out a similar phosphorylation reaction, but the substrates and regulation differ for each enzyme. | 89 | |
| 488519036 | protein kinase | One of a very large number of enzymes that transfers the terminal phosphate group of ATP to a specific amino acid side chain on a target protein. | 90 | |
| 488519037 | protein machine | A set of protein molecules that bind to each other in specific ways, so that concerted movements within the protein complex can carry out a sequence of reactions with unusual speed and effectiveness. A large number of the central reactions of the cell are catalyzed by such protein machines, with protein synthesis and DNA replication being particularly well understood examples. | 91 | |
| 488519038 | protein phosphotase | Enzyme that removes, by hydrolysis, a phosphate group from a protein, often with high specificity for the phosphorylated site. | 92 | |
| 488519039 | protein phosphorylation | The covalent addition of a phosphate group to a side chain of a protein catalyzed by a protein kinase. Phosphorylation usually alters the activity or properties of the protein in some way. | 93 | |
| 488519040 | proteomics | The large scale study of proteins, investigating many different proteins in a cell or tissue simultaneously. | 94 | |
| 488519041 | regulatory protein code | The set of covalent modifications that a protein has at any given time, which controls the behavior of the protein inside the cell. | 95 | |
| 488519042 | secondary structure | Regular local folding pattern of a polymeric molecule in proteins, it refers to α helices and β sheets. | 96 | |
| 488519043 | side chain | Portion of an amino acid not involved in making peptide bonds; the side chain gives each amino acid its unique properties. | 97 | |
| 488519044 | subunit | A monomer that forms part of a larger molecule, such as an amino acid residue in a protein or a nucleotide residue in a nucleic acid. Can also refer to a complete molecule that forms part of a larger molecule. Many proteins, for example, are composed of multiple polypeptide chains, each of which is called a protein subunit. | 98 | |
| 488519045 | transition state | Chemical structure that forms transiently in the course of a reaction and has the highest free energy of any reaction intermediate. | 99 | |
| 488519046 | X-ray crystallography | Technique used to determine three-dimensional protein structures by analyzing the diffraction pattern of a beam of X-rays passed through a crystal of the protein. | 100 | |
| 488519047 | acetyl CoA (acetyl coenzyme A) | Small water-soluble molecule that carries acetyl groups in cells. Contains an acetyl group linked to coenzyme A (CoA) by an easily hydrolyzable thioester bond. | 101 | |
| 488519048 | activated carrier | A small molecule used to carry energy or chemical groups in many different metabolic reactions. Examples include ATP, acetyl CoA and NADH | 102 | |
| 488519049 | activation energy | The extra energy that must be acquired by a molecule to undergo a particular chemical reaction. | 103 | |
| 488519050 | ADP (adenosine 5'-diphosphate) | Nucleotide that is produced by hydrolysis of the terminal phosphate of ATP. | 104 | |
| 488519051 | anabolism | Reaction pathways by which large molecules are made from smaller ones. Biosynthesis. | 105 | |
| 488519052 | biosynthesis | The formation of complex molecules from simple substances by living cells. | 106 | |
| 488519053 | catabolism | General term for the enzyme-catalyzed reactions in a cell by which complex molecules are degraded to simpler ones with release of energy. Intermediates in these catabolic reactions are sometimes called catabolites. | 107 | |
| 488519054 | catalysis | The acceleration of a chemical reaction due to the presence of a substance (the catalyst) that itself remains unchanged after the reaction. In cells, virtually all biochemical reactions are catalyzed (by enzymes) to enable them to occur at the temperature of living matter and within the timescale required. | 108 | |
| 488519055 | catalyst | Substance that accelerates a chemical reaction without itself undergoing a change. Enzymes are protein catalysts. | 109 | |
| 488519056 | coupled reaction | One of a linked pair of chemical reactions in which free energy released by one reaction serves to drive the other reaction. | 110 | |
| 488519057 | diffusion | The spread of molecules and small particles from one location to another by random, thermally driven movements. | 111 | |
| 488519058 | entropy | Thermodynamic quantity that measures the degree of disorder in a system; the higher the entropy, the more the disorder. | 112 | |
| 488519059 | enzyme | A protein that catalyzes a specific chemical reaction. | 113 | |
| 488519060 | equilibrium | In a chemical context, a state in which two or more reactions are proceeding at such a rate that they exactly balance each other and no net chemical change is occurring. | 114 | |
| 488519061 | equilibrium constant (K) | A number that characterizes the steady state reached by a reversible chemical reaction. Given by the ratio of forward and reverse rate constants of a reaction. | 115 | |
| 488519062 | free energy (G) | Energy that can be extracted from a system to do useful work, such as driving a chemical reaction. The standard free energy of a substance, G°, is its free energy measured at a defined concentration, temperature, and pressure. | 116 | |
| 488519063 | free-energy change (ΔG) | The difference in free energy between reactant and product molecules in a chemical reaction. A large negative value of ΔG indicates that the reaction has a strong tendency to occur. | 117 | |
| 488519064 | KM | The concentration of a substrate at which an enzyme works at half its maximum rate. Large values of KM usually indicate that the enzyme binds to its substrate with relatively low affinity. | 118 | |
| 488519065 | metabolism | The sum total of the chemical reactions that take place in the cells of a living organism resulting in growth, division, energy production, excretion of waste and so on. | 119 | |
| 488519066 | NAD+ (nicotine adenine dinucleotide) NADH (reduced nicotine adenine dinucleotide) | Activated carrier molecule that participates in an oxidation reaction by accepting a hydride ion (H+) from a donor molecule, thereby producing NADH. Widely used in the energy-producing breakdown of sugar molecules. | 120 | |
| 488519067 | NADP+ (nicotine adenine dinucleotide phosphate) NADPH (reduced nicotine adenine dinucleotide phosphate) | A carrier molecule closely related to NADH used as an electron donor in biosynthetic pathways. IN the process it is oxidized to NADP+. | 121 | |
| 488519068 | oxidation | Loss of electron density from an atom, as occurs during the addition of oxygen to a carbon atom or when a hydrogen is removed from a carbon atom. The opposite of reduction. | 122 | |
| 488519069 | photosynthesis | The process by which plants and some bacteria use the energy of sunlight to drive the synthesis of organic molecules from carbon dioxide and water. | 123 | |
| 488519070 | reduction | Addition of electron density to an atom, as occurs during the addition of hydrogen to a carbon atom or the removal of oxygen from it. The opposite of oxidation. | 124 | |
| 488519071 | respiration | Any process in a cell in which the uptake of molecular oxygen (O2) is coupled to the production of CO2. | 125 | |
| 488519072 | standard free-energy change ΔG° | The energy change measured at a defined concentration, temperature, and pressure. | 126 | |
| 488519073 | substrate | The molecule on which an enzyme acts. | 127 | |
| 488519074 | turnover number | In enzyme catalysis, the number of substrate molecules processed to product per second per enzyme molecule. Although different types of enzymes can have very different turnover numbers, turnover numbers of 1000 or more are quite common--a reflection of the impressive catalytic power of enzymes. | 128 | |
| 488519075 | Vmax | The maximum rate of an enzymatic reaction, attained immediately after the addition of substrate at a concentration sufficient to fully occupy the active sites of all enzyme molecules present. | 129 | |
| 488519076 | acid | In the context of cell biology, an organic molecule that dissociates in water to generate hydronium (H3O+) ions (thereby producing a low pH). | 130 | |
| 488519077 | amino acid | Organic molecule containing both an amino group and a carboxyl group. α-Amino acids (those in which the amino and carboxyl groups are linked to the same carbon atom) serve as the building blocks of proteins. | 131 | |
| 488519078 | atom | The smallest particle of an element that still retains its distinctive chemical properties. | 132 | |
| 488519079 | atomic weight | Mass of an atom expressed in daltons. | 133 | |
| 488519080 | ATP (adenosine 5'-triphosphate) | Nucleoside triphosphate composed of adenine, ribose, and three phosphate groups that is the principal carrier of chemical energy in cells. The terminal phosphate groups are highly reactive in the sense that their hydrolysis, or transfer to another molecule, is accompanied by the release of a large amount of free energy. | 134 | |
| 488519081 | Avogadro's number | The number of molecules in a quantity of substance equal to its molecular weight in grams. Approximately 6x10^23. | 135 | |
| 488519082 | base | Molecule that accepts a proton in solution. Also used to refer to the purine and pyrimidines in DNA and RNA, which are organic bases. | 136 | |
| 488519083 | buffer | Any weak acid or base that can release or take up protons, and thereby serve to maintain the pH under a variety of conditions. | 137 | |
| 488519084 | chemical bond | Chemical affinity between two atoms that holds them together. Types found in living cells include ionic bonds, covalent bonds, and hydrogen bonds. | 138 | |
| 488519085 | chemical group | Set of covalently linked atoms, such as hydroxyl group (-OH) or an amino group (-NH2) that occurs in many different molecules and the chemical behavior of which is well characterized. | 139 | |
| 488519086 | condensation reaction | Type of chemical reaction in which two organic molecules become linked to each other by a covalent bond with concomitant removal of a molecule of water. | 140 | |
| 488519087 | conformation | Spatial location of the atoms of a molecule relative to each other. The precise shape of a protein or other macromolecule in three dimensions. | 141 | |
| 488519088 | covalent bond | Stable chemical link between two atoms produced by sharing one or more pairs of electrons. | 142 | |
| 488519089 | electron | Fundamental subatomic particle with a unit negative charge (e-). | 143 | |
| 488519090 | electrostatic attraction | Attractive force that occurs between oppositely charged atoms. Examples are ionic bonds and the attractions between molecules containing polar covalent bonds. | 144 | |
| 488519091 | fatty acid | Compound such as palmitic acid that has a carboxylic acid attached to a long hydrocarbon chain. Used as a major source of energy during metabolism and as a starting point for the synthesis of phospholipids. | 145 | |
| 488519092 | hydrogen bond | A weak noncovalent chemical bond between an electronegative atom such as nitrogen or oxygen and a hydrogen atom bound to another electronegative atom. | 146 | |
| 488519093 | hydrolysis | Cleavage of a covalent bond with accompanying addition of water, -H being added to one product of the cleavage and -OH to the other. | 147 | |
| 488519094 | hydronium ion (H3O+) | The form taken by a proton (H+) in aqueous solution. | 148 | |
| 488519095 | hydrophilic | Polar molecule or part of a molecule that forms enough hydrogen bonds to water to dissolve readily in water. | 149 | |
| 488519096 | hydrophobic | Nonpolar molecule or part of a molecule that cannot form favorable bonding interactions with water molecules and therefore does not dissolve in water. | 150 | |
| 488519097 | ion | An atom carrying an electrical charge, either positive or negative. | 151 | |
| 488519098 | ionic bond | Attractive force that holds together two ions, one positive, the other negative. | 152 | |
| 488519099 | macromolecule | Molecule such as a protein, nucleic acid, or polysaccharide with a molecular mass greater than a few thousand daltons. | 153 | |
| 488519100 | molecule | Group of atoms joined together by covalent bonds. | 154 | |
| 488519101 | molecular weight | Mass of a molecule expressed in daltons. | 155 | |
| 488519102 | monomer | Small molecule that can be linked to others of a similar type to form a larger molecule (polymer). | 156 | |
| 488519103 | noncovalent bond | Chemical bond in which, in contrast with a covalent bond, no electrons are shared. Noncovalent bonds are relatively weak, but they can sum together to produce strong, highly specific interactions between molecules. Examples are hydrogen bonds and van der Waals interactions. | 157 | |
| 488519104 | nucleotide | Nucleoside with a series of one or more phosphate group joined by an ester linkage to the sugar moiety. DNA and RNA are polymers of nucleotides. | 158 | |
| 488519105 | pH scale | Scale used to measure the acidity of a solution: "p" refers to the power of 10, "H" to hydrogen. Defined as the negative logarithm of the hydrogen ion concentration in moles per liter (M). | 159 | |
| 488519106 | polar | Describes a molecule, or a covalent bond in a molecule, in which bonding electrons are attracted more strongly to specific atoms, thereby creating an uneven (or polarized) distribution of electric charge. | 160 | |
| 488519107 | polymer | Large and unusually linear molecule made by the repetitive assembly, using covalent bonds, of multiple identical or similar subunits (monomers). | 161 | |
| 488519108 | proton | Subatomic particle found in the atomic nucleus, Also exists as an independent chemical species as the positive hydrogen ion (H+). | 162 | |
| 488519109 | sequence | The linear order of monomers in a large molecule, for example amino acids in a protein or nucleotides in DNA. In general the sequence of a macromolecule specifies its precise biological function. | 163 | |
| 488519110 | subunit | A monomer that forms part of a larger molecule, such as an amino acid residue in a protein or a nucleotide residue in a nucleic acid. Can also refer to a complete molecule that forms part of a larger molecule. Many proteins, for example, are composed of multiple polypeptide chains, each of which is called a protein subunit. | 164 | |
| 488519111 | sugar | A substance made of carbon, hydrogen, and oxygen with the general formula (CH2O)n. A carbohydrate or saccharide. The "sugar" of everyday usage is sucrose, a specific sweet-tasting disaccharide produced by beet or sugar cane. | 165 | |
| 488519112 | archaea | One of the two divisions of prokaryote, often found in hostile environments such as hot springs or concentrated brine. | 166 | |
| 488519113 | bacteria | Commonly used name for any prokaryotic organism, but more precisely refers to the eubacteria, the "true bacteria," one of the three major domains of life. Most are single-celled organisms. Some species of bacteria cause disease. | 167 | |
| 488519114 | cell | The basic unit from which living organisms are made, consisting of an aqueous solution of organic molecules enclosed by a membrane. All cells arise from existing cells, usually by a process of division. | 168 | |
| 488519115 | chloroplast | Specialized organelle in algae and plants that contains chlorophyll and in which photosynthesis takes place. | 169 | |
| 488519116 | chromosome | Long threadlike structure composed of DNA and associated proteins that carries the genetic information of an organism. Especially visible when plant and animal cells undergo mitosis and meiosis. | 170 | |
| 488519117 | cytoplasm | Contents of a cell that are contained within its plasma membrane but, in the case of eukaryotic cells, outside the nucleus. | 171 | |
| 488519118 | cytoskeleton | System of protein filaments in the cytoplasm of a eukaryotic cell that gives the cell shape and the capacity for directed movement. Its most abundant components are actin filaments, microtubules, and intermediate filaments. | 172 | |
| 488519119 | cytosol | Contents of the main compartment of the cytoplasm, excluding membrane-enclosed organelles such as endoplasmic reticulum and mitochondria. The cell fraction remaining after membranes, cytoskeletal components, and other organelles have been removed. | 173 | |
| 488519120 | DNA (deoxyribonucleic acid) | Double-stranded polynucleotide formed when two separate chains of covalently linked deoxyribonucleotide units. It serves as the cell's store of genetic information that is transmitted from generation to generation. | 174 | |
| 488519121 | eucaryote | Living organism composed of one or more cells with a distinct nucleus and cytoplasm. Includes all forms of life except archaea and bacteria (the prokaryotes) and viruses. | 175 | |
| 488519122 | evolution | The gradual change in living organisms taking place over generations that result in new species being formed. | 176 | |
| 488519123 | genome | The total genetic information carried by a cell or an organism (or the DNA molecules that carry this information). | 177 | |
| 488519124 | homologous | Describes organs or molecules that are similar because of their common evolutionary origin. Specifically it describes similarities between protein sequences or nucleic acid sequences. | 178 | |
| 488519125 | micrometer (μm) | Unit of measurement often applied to cells and organelles. Equal to 10^-6 meter. | 179 | |
| 488519126 | microscope | Instrument for viewing extremely small objects. Light microscope utilizes a focused beam of visible light and is used to examine cells and organelles. An electron microscope utilizes a beam of electrons and can be used to examine objects as small as individual molecules. | 180 | |
| 488519127 | mitochondrion | Membrane-enclosed organelle, about the size of a bacterium, that carries out oxidative phosphorylation and produces most of the ATP in eukaryotic cells. | 181 | |
| 488519128 | model organism | An organism selected for intensive study as a representative of a large group of species. Examples are the mouse (representing mammals), the yeast (representing a unicellular eucaryote), and Escherichia coli (representing bacteria). | 182 | |
| 488519129 | nanometer (nm) | Unit of length commonly used to measure molecules and cell organelles. Equal to 10^-9 meters. | 183 | |
| 488519130 | nucleus | The major organelle of a eukaryotic cell, which contains DNA organized into chromosomes. Also, when referring to an atom, the central mass built from neutrons and protons. | 184 | |
| 488519131 | organelle | A discrete structure or subcompartment of a eukaryotic cell (especially one that is visible in the light microscope) that is specialized to carry out a particular function. Examples include mitochondria and the Golgi apparatus. | 185 | |
| 488519132 | procaryote | Major category of living cells distinguished by the absence of a nucleus. Procaryotes comprise the archaea and the eubacteria (commonly called bacteria), two of the three domains of life. | 186 | |
| 488519133 | protein | The major macromolecular constituent of cells. Each protein is composed of one or more linear chains of amino acids linked together by peptide bonds in a specific sequence. The amino acid chain is folded into a 3D shape that is unique to the given protein and determines its function. | 187 | |
| 488519134 | protozoan | A member of the protozoan--free-living, non photosynthetic, single celled, motile eucaryotic organisms. Many protozoans live by feeding on other organisms. | 188 | |
| 488519135 | ribosome | Particle composed of ribosomal RNAs and ribosomal proteins that associate with messenger RNA and catalyzes the synthesis of protein. | 189 | |
| 488519136 | RNA (ribonucleic acid) | A (usually) single-stranded polynucleotide in the form of a chain of covalently linked ribonucleotide subunits. It is synthesized when an RNA polymerase copies the nucleotide sequence of DNA. RNA serves a variety of functions in cells: messenger RNA, microRNA, ribosomal RNA, transfer RNA. | 190 |
