Term
| Biology (Chapter 1 start) |
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Definition
| The scientific study of life |
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Term
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Definition
| Descent with modification; the idea that living species are descendants of ancestral species that were different from the present-day ones; also defined more narrowly as the change in the genetic composition of a population from generation to generation. |
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Term
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Definition
| The use of computers, software, and mathematical models to process and integrate biological information from large data sets. |
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Term
| deoxyribonucleic acid (DNA) |
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Definition
| (de-ok´-se-ri´-bo-nu-kla´-ik) A double-stranded, helical nucleic acid molecule consisting of nucleotide monomers with a deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T); capable of replicating and determining the inherited structure of a cell’s proteins. |
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Term
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Definition
| New properties that arise with each step upward in the hierarchy of life, owing to the arrangement and interactions of parts as complexity increases. |
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Term
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Definition
| (yu'-ker-e-ot'-ik) A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with eukaryotic cells (protists, plants, fungi, and animals) are called eukaryotes. |
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Term
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Definition
| A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses). |
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Term
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Definition
| (je´-nom) The genetic material of an organism or virus; the complete complement of an organism’s or virus’s genes along with its noncoding nucleic acid sequences. |
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Term
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Definition
| A primary mechanism of homeostasis, whereby a change in a physiological variable triggers a response that counteracts the initial change. |
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Term
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Definition
| A physiological control mechanism in which a change in a variable triggers mechanisms that amplify the change. |
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Term
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Definition
| (pro´-kar´-e-ot´-ik) A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with prokaryotic cells (bacteria and archaea) are called prokaryotes. |
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Term
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Definition
| An approach to studying biology that aims to model the dynamic behavior of whole biological systems. |
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Term
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Definition
| Period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill vacant ecological roles in their communities. |
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Term
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Definition
| (ar´-k e´-uh) One of two prokaryotic domains, the other being Bacteria. |
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Term
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Definition
| Member of the prokaryotic domain Archaea. |
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Term
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Definition
| One of two prokaryotic domains, the other being Archaea. |
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Term
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Definition
| In classification, the taxonomic category above the level of order. |
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Term
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Definition
| (1) A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya. (2) An independently folding part of a protein. |
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Term
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Definition
| (yu-kar'-e-uh) The domain that includes all eukaryotic organisms. |
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Term
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Definition
| In classification, the taxonomic category above genus. |
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Term
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Definition
| (je´-nus) (plural, genera) A taxonomic category above the species level, designated by the first word of a species’ two-part scientific name. |
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Term
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Definition
| A taxonomic category, the second broadest after domain. |
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Term
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Definition
| In classification, the taxonomic category above the level of family. |
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Term
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Definition
| (fi´-lum) (plural, phyla) In classification, the taxonomic category above class. |
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Term
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Definition
| (spe´-sez) A population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not produce viable, fertile offspring with members of other such groups. |
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Term
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Definition
| An experiment in which an experimental group is compared with a control group that varies only in the factor being tested. |
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Term
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Definition
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Term
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Definition
| A type of logic in which specific results are predicted from a general premise. |
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Term
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Definition
| The process of scientific inquiry that focuses on describing nature. |
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Term
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Definition
| (hi-poth'-uh-sis) A tentative answer to a well-framed question, narrower in scope than a theory and subject to testing. |
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Term
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Definition
| A type of logic in which generalizations are based on a large number of specific observations. |
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Term
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Definition
| The search for information and explanation, often focused by specific questions. |
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Term
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Definition
| A representation of a theory or process. |
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Term
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Definition
| An explanation that is broad in scope, generates new hypotheses, and is supported by a large body of evidence. |
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Term
| Compound (Chapter 2 start) |
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Definition
| A substance consisting of two or more different elements combined in a fixed ratio. |
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Term
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Definition
| Any substance that cannot be broken down to any other substance by chemical reactions. |
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Term
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Definition
| Anything that takes up space and has mass. |
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Term
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Definition
| An element indispensable for life but required in extremely minute amounts. |
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Term
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Definition
| The smallest unit of matter that retains the properties of an element. |
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Term
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Definition
| The total mass of an atom, which is the mass in grams of 1 mole of the atom. |
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Term
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Definition
| An atom’s dense central core, containing protons and neutrons. |
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Term
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Definition
| The number of protons in the nucleus of an atom, unique for each element and designated by a subscript to the left of the elemental symbol. |
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Term
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Definition
| A measure of mass for atoms and subatomic particles; the same as the atomic mass unit, or amu. |
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Term
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Definition
| A subatomic particle with a single negative electrical charge and a mass about 1/2,000 that of a neutron or proton. One or more electrons move around the nucleus of an atom. |
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Term
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Definition
| An energy level of electrons at a characteristic average distance from the nucleus of an atom. |
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Term
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Definition
| The capacity to cause change, especially to do work (to move matter against an opposing force). |
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Term
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Definition
| (i´-so-top´) One of several atomic forms of an element, each with the same number of protons but a different number of neutrons, thus differing in atomic mass. |
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Term
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Definition
| The sum of the number of protons and neutrons in an atom’s nucleus. |
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Term
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Definition
| A subatomic particle having no electrical charge (electrically neutral), with a mass of about 1.7 × 10-24 g, found in the nucleus of an atom. |
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Term
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Definition
| The three-dimensional space where an electron is found 90% of the time. |
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Term
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Definition
| The energy that matter possesses as a result of its location or spatial arrangement (structure). |
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Term
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Definition
| (pro´-ton) A subatomic particle with a single positive electrical charge, with a mass of about 1.7 × 10-24 g, found in the nucleus of an atom. |
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Term
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Definition
| An isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy. |
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Term
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Definition
| An electron in the outermost electron shell. |
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Term
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Definition
| The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom. |
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Term
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Definition
| (an´-i-on) A negatively charged ion. |
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Term
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Definition
| (cat´-i-on) A positively charged ion. |
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Term
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Definition
| An attraction between two atoms, resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms. The bonded atoms gain complete outer electron shells. |
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Term
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Definition
| (ko-va´-lent) A type of strong chemical bond in which two atoms share one or more pairs of valence electrons. |
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Term
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Definition
| A double covalent bond; the sharing of two pairs of valence electrons by two atoms. |
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Term
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Definition
| The attraction of a given atom for the electrons of a covalent bond. |
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Term
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Definition
| A type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule. |
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Term
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Definition
| (i´-on) An atom or group of atoms that has gained or lost one or more electrons, thus acquiring a charge. |
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Term
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Definition
| (i-on´-ik) A chemical bond resulting from the attraction between oppositely charged ions. |
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Term
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Definition
| A compound resulting from the formation of an ionic bond; also called a salt |
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Term
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Definition
| A type of molecular notation representing the quantity of constituent atoms, but not the nature of the bonds that join them. |
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Term
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Definition
| Two or more atoms held together by covalent bonds. |
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Term
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Definition
| A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity. |
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Term
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Definition
| A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive. |
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Term
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Definition
| A compound resulting from the formation of an ionic bond; also called an ionic compound. |
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Term
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Definition
| A single covalent bond; the sharing of a pair of valence electrons by two atoms. |
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Term
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Definition
| A type of molecular notation in which the constituent atoms are joined by lines representing covalent bonds. |
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Term
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Definition
| The bonding capacity of a given atom; usually equals the number of unpaired electrons required to complete the atom’s outermost (valence) shell. |
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Term
| Van der Waals interactions |
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Definition
| Weak attractions between molecules or parts of molecules that result from localized charge fluctuations. |
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Term
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Definition
| In a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time. |
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Term
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Definition
| The making and breaking of chemical bonds, leading to changes in the composition of matter. |
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Term
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Definition
| A material resulting from a chemical reaction. |
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Term
| Reaction (End of Chapter 2) |
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Definition
| A starting material in a chemical reaction. |
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Term
| Electronegativity (Start of Chapter 3) |
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Definition
| The attraction of a given atom for the electrons of a covalent bond. |
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Term
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Definition
| A type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule. |
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Term
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Definition
| A molecule (such as water) with opposite charges on different ends of the molecule. |
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Term
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Definition
| The attraction between different kinds of molecules. |
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Term
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Definition
| (a´-kwe-us) A solution in which water is the solvent. |
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Term
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Definition
| The amount of heat energy required to raise the temperature of 1 g of water by 1°C; also the amount of heat energy that 1 g of water releases when it cools by 1°C. The Calorie (with a capital C), usually used to indicate the energy content of food, is a kilocalorie. |
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Term
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Definition
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Term
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Definition
| The binding together of like molecules, often by hydrogen bonds. |
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Term
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Definition
| A mixture made up of a liquid and particles that (because of their large size) remain suspended rather than dissolved in that liquid. |
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Term
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Definition
| The process by which a liquid changes to a gas. |
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Term
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Definition
| The process in which the surface of an object becomes cooler during evaporation, owing to a change of the molecules with the greatest kinetic energy from the liquid to the gaseous state. |
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Term
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Definition
| The total amount of kinetic energy due to the random motion of atoms or molecules in a body of matter; also called thermal energy. Heat is energy in its most random form. |
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Term
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Definition
| The quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state. |
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Term
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Definition
| The sphere of water molecules around a dissolved ion |
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Term
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Definition
| (hi´-dro-fil´-ik) Having an affinity for water. |
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Term
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Definition
| (hi´-dro-fo´-bik) Having an aversion to water; tending to coalesce and form droplets in water. |
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Term
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Definition
| A unit of energy: 1 J = 0.239 cal; 1 cal = 4.184 J. |
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Term
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Definition
| A thousand calories; the amount of heat energy required to raise the temperature of 1 kg of water by 1°C. |
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Term
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Definition
| (kuh-net´-ik) The energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter. |
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Term
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Definition
| A common measure of solute concentration, referring to the number of moles of solute per liter of solution. |
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Term
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Definition
| The number of grams of a substance that equals its molecular weight in daltons and contains Avogadro’s number of molecules. |
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Term
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Definition
| The sum of the masses of all the atoms in a molecule; sometimes called molecular weight. |
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Term
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Definition
| (sol'-yut) A substance that is dissolved in a solution. |
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Term
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Definition
| A liquid that is a homogeneous mixture of two or more substances. |
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Term
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Definition
| The dissolving agent of a solution. Water is the most versatile solvent known. |
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Term
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Definition
| The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1°C. |
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Term
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Definition
| A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules. |
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Term
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Definition
| A measure of the intensity of heat in degrees, reflecting the average kinetic energy of the molecules. |
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Term
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Definition
| A substance that increases the hydrogen ion concentration of a solution. |
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Term
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Definition
| Rain, snow, or fog that is more acidic than pH 5.2 |
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Term
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Definition
| A substance that reduces the hydrogen ion concentration of a solution. |
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Term
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Definition
| A substance that consists of acid and base forms in a solution and that minimizes changes in pH when extraneous acids or bases are added to the solution. |
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Term
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Definition
| A single proton with a charge of 1+. The dissociation of a water molecule (H2O) leads to the generation of a hydroxide ion (OH–) and a hydrogen ion (H+). |
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Term
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Definition
| A water molecule that has an extra proton bound to it; H3O+. |
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Term
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Definition
| A water molecule that has lost a proton; OH–. |
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Term
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Definition
| A measure of hydrogen ion concentration equal to –log [H+] and ranging in value from 0 to 14. |
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Term
| Enantiomer ( Start of Chapter 4) |
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Definition
| (en-an´-te-o-mer) One of two compounds that are mirror images of each other. |
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Term
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Definition
| One of several compounds that have the same molecular formula and covalent arrangements but differ in the spatial arrangements of their atoms owing to the inflexibility of double bonds. |
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Term
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Definition
| An organic molecule consisting only of carbon and hydrogen. |
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Term
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Definition
| (i´-so-mer) One of several compounds with the same molecular formula but different structures and therefore different properties. The three types of isomers are structural isomers, geometric isomers, and enantiomers. |
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Term
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Definition
| One of several compounds that have the same molecular formula but differ in the covalent arrangements of their atoms. |
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Term
| Adenosine triphosphate (ATP) |
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Definition
| (a-den´-o-sen tri fos´-fat) An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells. |
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Term
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Definition
| A chemical group consisting of a nitrogen atom bonded to two hydrogen atoms; can act as a base in solution, accepting a hydrogen ion and acquiring a charge of 1+. |
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Term
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Definition
| (kar-buh-nel´) A chemical group present in aldehydes and ketones and consisting of a carbon atom double-bonded to an oxygen atom. |
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Term
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Definition
| (kar-bok-sil) A chemical group present in organic acids and consisting of a single carbon atom double-bonded to an oxygen atom and also bonded to a hydroxyl group. |
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Term
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Definition
| A specific configuration of atoms commonly attached to the carbon skeletons of organic molecules and usually involved in chemical reactions. |
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Term
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Definition
| (hi-drok´-sil) A chemical group consisting of an oxygen atom joined to a hydrogen atom. Molecules possessing this group are soluble in water and are called alcohols. |
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Term
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Definition
| A chemical group consisting of a carbon bonded to three hydrogen atoms. The methyl group may be attached to a carbon or to a different atom. |
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Term
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Definition
| A chemical group consisting of a phosphorus atom bonded to four oxygen atoms; important in energy transfer. |
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Term
| Sulfhydryl group (End of Chapter 4) |
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Definition
| A chemical group consisting of a sulfur atom bonded to a hydrogen atom. |
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Term
| Macromolecule (Start of Chapter 5) |
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Definition
| A giant molecule formed by the joining of smaller molecules, usually by a condensation reaction. Polysaccharides, proteins, and nucleic acids are macromolecules. |
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Term
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Definition
| A reaction in which two molecules become covalently bonded to each other through the loss of a small molecule, usually water, in which case it is also called a dehydration reaction. |
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Term
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Definition
| A chemical reaction in which two molecules covalently bond to each other with the removal of a water molecule. |
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Term
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Definition
| (en´-zim) A macromolecule serving as a catalyst, a chemical agent that changes the rate of a reaction without being consumed by the reaction. |
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Term
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Definition
| (hi-drol´-uh-sis) A chemical process that lyses, or splits, molecules by the addition of water, functioning in disassembly of polymers to monomers. |
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Term
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Definition
| (mon´-uh-mer) The subunit that serves as the building block of a polymer. |
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Term
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Definition
| (pol´-uh-mer) A long molecule consisting of many similar or identical monomers linked together. |
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Term
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Definition
| (kar´-bo-hi´-drat) A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides). |
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Term
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Definition
| (sel´-yu-los) A structural polysaccharide of plant cell walls, consisting of glucose monomers joined by β glycosidic linkages. |
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Term
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Definition
| (ki´-tin) A structural polysaccharide, consisting of amino sugar monomers, found in many fungal cell walls and in the exoskeletons of all arthropods. |
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Term
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Definition
| (di-sak´-uh-rid) A double sugar, consisting of two monosaccharides joined by a glycosidic linkage formed during dehydration synthesis. |
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Term
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Definition
| (gli´-ko-jen) An extensively branched glucose storage polysaccharide found in the liver and muscle of animals; the animal equivalent of starch. |
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Term
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Definition
| A covalent bond formed between two monosaccharides by a dehydration reaction. |
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Term
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Definition
| (mon´-o-sak´-uh-rid) The simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides. Also known as simple sugars, monosaccharides have molecular formulas that are generally some multiple of CH2O. |
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Term
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Definition
| (pol´-e-sak´-uh-rid) A polymer of many monosaccharides, formed by dehydration reactions. |
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Term
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Definition
| A storage polysaccharide in plants, consisting entirely of glucose monomers joined by a glycosidic linkages. |
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Term
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Definition
| A cardiovascular disease in which fatty deposits called plaques develop in the inner walls of the arteries, obstructing the arteries and causing them to harden. |
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Term
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Definition
| (ko-les´-tuh-rol) A steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids, such as hormones. |
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Term
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Definition
| A lipid consisting of three fatty acids linked to one glycerol molecule; also called a triacylglycerol or triglyceride. |
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Term
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Definition
| A long carbon chain carboxylic acid. Fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form a fat molecule, also known as a triacylglycerol or triglyceride. |
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Term
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Definition
| (lip´-id) One of a group of compounds, including fats, phospholipids, and steroids, that mix poorly, if at all, with water. |
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Term
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Definition
| (fos´-fo-lip´-id) A lipid made up of glycerol joined to two fatty acids and a phosphate group. The hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head. Phospholipids form bilayers that function as biological membranes. |
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Term
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Definition
| A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms that are attached to the carbon skeleton. |
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Term
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Definition
| a type of lipid characterized by a carbon skeleton consisting of four rings with various chemical groups attached. |
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Term
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Definition
| An unsaturated fat containing one or more trans double bonds. |
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Term
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Definition
| (tri-as´-ul-glis´-uh-rol) Three fatty acids linked to one glycerol molecule; also called a fat or a triglyceride. |
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Term
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Definition
| A fatty acid possessing one or more double bonds between the carbons in the hydrocarbon tail. Such bonding reduces the number of hydrogen atoms attached to the carbon skeleton. |
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Term
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Definition
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Term
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Definition
| (uh-men´-o) An organic molecule possessing both carboxyl and amino groups. Amino acids serve as the monomers of polypeptides. |
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Term
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Definition
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Term
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Definition
| (kat'-uh-list ) A chemical agent that increases the rate of a reaction without being consumed by the reaction. |
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Term
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Definition
| (shap'-er-o'-nin) A protein molecule that assists in the proper folding of other proteins. |
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Term
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Definition
| (de-na´-chur-a´-shun) In proteins, a process in which a protein unravels and loses its native shape, thereby becoming biologically inactive; in DNA, the separation of the two strands of the double helix. Denaturation occurs under extreme (noncellular) conditions of pH, salt concentration, and temperature. |
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Term
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Definition
| A strong covalent bond formed when the sulfur of one cysteine monomer bonds to the sulfur of another cysteine monomer. |
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Term
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Definition
| A type of weak chemical bond formed when molecules that do not mix with water coalesce to exclude water. |
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Term
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Definition
| The covalent bond between the carboxyl group on one amino acid and the amino group on another, formed by a dehydration reaction. |
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Term
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Definition
| (pol´-e-pep´-tid) A polymer (chain) of many amino acids linked together by peptide bonds. |
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Term
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Definition
| The level of protein structure referring to the specific sequence of amino acids. |
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Term
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Definition
| (pro´-ten) A functional biological molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure. |
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Term
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Definition
| (kwot- er-n ar- e) The particular shape of a complex, aggregate protein, defined by the characteristic three-dimensional arrangement of its constituent subunits, each a polypeptide. |
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Term
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Definition
| The localized, repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bond formation between constituents of the backbone. |
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Term
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Definition
| Irregular contortions of a protein molecule due to interactions of side chains involved in hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges. |
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Term
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Definition
| A technique that depends on the diffraction of an X-ray beam by the individual atoms of a crystallized molecule to study the three-dimensional structure of the molecule. |
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Term
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Definition
| The opposite arrangement of the sugar-phosphate backbones in a DNA double helix. |
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Term
| deoxyribonucleic acid (DNA) |
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Definition
| (de-ok´-se-ri´-bo-nu-kla´-ik) A double-stranded, helical nucleic acid molecule consisting of nucleotide monomers with a deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T); capable of replicating and determining the inherited structure of a cell’s proteins. |
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Term
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Definition
| (de-ok'-si-ri'-bos) The sugar component of DNA nucleotides, having one fewer hydroxyl group than ribose, the sugar component of RNA nucleotides. |
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Term
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Definition
| The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape. |
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Term
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Definition
| A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses). |
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Term
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Definition
| (nu-kla´-ik) A polymer (polynucleotide) consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA. |
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Term
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Definition
| (nu´-kle-o-tid´) The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group. |
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Term
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Definition
| (pol´-e-nu´-kle-o-tid) A polymer consisting of many nucleotide monomers in a chain; nucleotides can be those of DNA or RNA. |
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Term
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Definition
| (pyu´-ren) One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a five-membered ring. Adenine (A) and guanine (G) are purines. |
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Term
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Definition
| (puh-rim´-uh-den) One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring. Cytosine (C), thymine (T), and uracil (U) are pyrimidines. |
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Term
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Definition
| (ri´-bo-nu-kla´-ik) A type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis, gene regulation, and as the genome of some viruses. |
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Term
| Ribose (End of Chapter 5) |
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Definition
| The sugar component of RNA nucleotides. |
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Term
| Electron microscope (EM) (Start of chapter 6) |
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Definition
| A microscope that uses magnets to focus an electron beam on or through a specimen, resulting in resolving power a thousandfold greater than that of a light microscope. A transmission electron microscope (TEM) is used to study the internal structure of thin sections of cells. A scanning electron microscope (SEM) is used to study the fine details of cell surfaces. |
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Definition
| An optical instrument with lenses that refract (bend) visible light to magnify images of specimens. |
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Definition
| (or-guh-nel´) Any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells. |
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| Scanning electron microscope (SEM) |
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Definition
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Term
| Transmission electron microscope (TEM) |
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Definition
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Definition
| (1) A sticky layer that surrounds the cell wall of some prokaryotes, protecting the cell surface and sometimes helping to glue the cell to surfaces. (2) The sporangium of a bryophyte (moss, liverwort, or hornwort). |
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Definition
| (si´-to-plaz´-um) The contents of the cell, exclusive of the nucleus and bounded by the plasma membrane. |
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Definition
| (si´-to-sol) The semifluid portion of the cytoplasm. |
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Term
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Definition
| (yu'-ker-e-ot'-ik) A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with eukaryotic cells (protists, plants, fungi, and animals) are called eukaryotes. |
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Term
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Definition
| (nu'-kle-oyd) A dense region of DNA in a prokaryotic cell. |
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Definition
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Definition
| The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell’s chemical composition. |
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Definition
| One of a family of closely related organelles that includes chloroplasts, chromoplasts, and amyloplasts (leucoplasts). Plastids are found in cells of photosynthetic organisms. |
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Term
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Definition
| (pro´-kar´-e-ot´-ik) A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with prokaryotic cells (bacteria and archaea) are called prokaryotes. |
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Term
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Definition
| (kro´-muh-tin) The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope. |
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Term
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Definition
| (kro´-muh-som) A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each chromosome consists of one very long DNA molecule and associated proteins. (A bacterial chromosome usually consists of a single circular DNA molecule and associated proteins. It is found in the nucleoid region, which is not membrane bounded.) See also chromatin. |
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Definition
| The double membrane in a eukaryotic cell that encloses the nucleus, separating it from the cytoplasm. |
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Definition
| A netlike array of protein filaments lining the inner surface of the nuclear envelope; it helps maintain the shape of the nucleus. |
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Term
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Definition
| (nu-kle´-o-lus) (plural, nucleoli) A specialized structure in the nucleus, consisting of chromatin regions containing ribosomal RNA genes along with ribosomal proteins imported from the cytoplasmic site of rRNA synthesis and ribosomal subunit assembly. See also ribosome. |
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Definition
| (1) An atom’s central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons. |
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Definition
| (ri´-buh-so´-mul) The most abundant type of RNA, which together with proteins makes up ribosomes. |
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Term
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Definition
| (ri'-buh-som') A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus. See also nucleolus. |
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