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70 Cards in this Set
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actin
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A globular protein that links into chains, two of which twist helically about each other, forming microfilaments (actin filaments) in muscle and other kinds of cells.
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basal body
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A eukaryotic cell structure consisting of a 9 + 0 arrangement of microtubule triplets. It may organize the microtubule assembly of a cilium or flagellum and is structurally very similar to a centriole.
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capsule
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A sticky layer that surrounds the cell wall of some prokaryotes, protecting the cell surface and sometimes helping to glue the cell to surfaces.
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cell fractionation
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The disruption of a cell and separation of its parts by centrifugation.
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central vacuole
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A membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development.
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centriole
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A structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a 9 + 0 pattern. A centrosome has a pair of these.
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centrosome
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Structure present in the cytoplasm of animal cells, important during cell division; functions as a microtubule-organizing center. It has two centrioles.
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chloroplast
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An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
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chromatin
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The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, it 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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chromosome
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A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each consists of one very long DNA molecule and associated proteins. (In bacteria, it usually consists of a single circular DNA molecule and associated proteins. It is found in the nucleoid region, which is not membrane bounded.)
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cilium (pl., cilia)
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A short cellular appendage containing microtubules. A motile version is specialized for locomotion and is formed from a core of nine outer doublet microtubules and two inner single microtubules (the “9 + 2” arrangement) ensheathed in an extension of the plasma membrane. A primary version is usually nonmotile and plays a sensory and signaling role; it lacks the two inner microtubules (the “9 + 0” arrangement).
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collagen
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A glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone; the most abundant protein in the animal kingdom.
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contractile vacuole
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A membranous sac that helps move excess water out of certain freshwater protists.
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crista (pl., cristae)
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An infolding of the inner membrane of a mitochondrion that houses electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP (ATP synthase).
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cytoplasm
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The contents of the cell, exclusive of the nucleus and bounded by the plasma membrane.
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cytoplasmic streaming
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A circular flow of cytoplasm, involving myosin and actin filaments, that speeds the distribution of materials within cells.
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cytoskeleton
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A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions.
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cytosol
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The semifluid portion of the cytoplasm.
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desmosome
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A type of intercellular junction in animal cells that functions as a rivet.
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dynein
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In cilia and flagella, a large contractile protein extending from one microtubule doublet to the adjacent doublet. ATP hydrolysis drives changes in its shape that lead to bending of cilia and flagella.
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electron microscope (EM)
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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.
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endomembrane system
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The collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles; includes the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles.
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endoplasmic reticulum (ER)
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An extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.
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eukaryotic cell
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A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles.
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extracellular matrix (ECM)
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The substance in which animal cells are embedded, consisting of protein and polysaccharides synthesized and secreted by cells.
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fibronectin
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A glycoprotein that helps animal cells attach to the extracellular matrix.
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flagellum (pl., flagella)
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A long cellular appendage specialized for locomotion. In eukaryotes, like motile cilia, they have a core with nine outer doublet microtubules and two inner single microtubules ensheathed in an extension of the plasma membrane. In prokaryotes, they have a different structure.
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food vacuole
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A membranous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell.
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gap junction
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A type of intercellular junction in animals that allows the passage of materials between cells.
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glycoprotein
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A protein with one or more carbohydrates covalently attached to it.
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Golgi apparatus
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An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncellulose carbohydrates.
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granum (pl., grana)
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A stack of membrane-bounded thylakoids in the chloroplast. They function in the light reactions of photosynthesis.
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integrin
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in animal cells, a transmembrane receptor protein that interconnects the extracellular matrix and the cytoskeleton.
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intermediate filament
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A component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments.
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light microscope (LM)
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An optical instrument with lenses that refract (bend) visible light to magnify images of specimens.
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lysosome
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A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists.
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microfilament
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A cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction; also known as an actin filament.
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microtubule
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A hollow rod composed of tubulin proteins that make up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella.
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middle lamella
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In plants, a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young cells.
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mitochondrial matrix
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The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle.
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mitochondrion (pl., mitochondria)
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An organelle in eukaryotic cells that serves as the site of cellular respiration.
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motor protein
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A protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell.
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nuclear envelope
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The double membrane in a eukaryotic cell that encloses the nucleus, separating it from the cytoplasm.
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nuclear lamina
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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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nucleoid
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A dense region of DNA in a prokaryotic cell.
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nucleolus (pl., nucleoli)
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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.
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nucleus
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The chromosome-containing organelle of a eukaryotic cell.
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organelle
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Any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells.
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peroxisome
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An organelle containing enzymes that transfer hydrogen (H<sub>2</sub>) from various substrates to oxygen (O<sub>2</sub>), producing and then degrading hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>).
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phagocytosis
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A type of endocytosis in which large particulate substances are taken up by a cell. It is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells).
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plasma membrane
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The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell’s chemical composition.
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plasmodesma (pl., plasmodesmata)
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An open channel in the cell wall of a plant through which strands of cytosol connect from an adjacent cell.
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plastid
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One of a family of closely related organelles that includes chloroplasts, chromoplasts, and amyloplasts (leucoplasts). They are found in cells of photosynthetic organisms.
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primary cell wall
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In plants, a relatively thin and flexible layer first secreted by a young cell.
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prokaryotic cell
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A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles.
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proteoglycan
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A glycoprotein consisting of a small core protein with many carbohydrate chains attached, found in the extracellular matrix of animal cells. It may consist of up to 95% carbohydrate.
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pseudopodium (pl., pseudopodia)
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A cellular extension of amoeboid cells used in moving and feeding.
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ribosomal RNA (rRNA)
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The most abundant type of RNA, which together with proteins makes up ribosomes.
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ribosome
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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.
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rough ER
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That portion of the endoplasmic reticulum studded with ribosomes.
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scanning electron microscope (SEM)
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A microscope that uses an electron beam to scan the surface of a sample to study details of its topography.
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secondary cell wall
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In plants, a strong and durable matrix often deposited in several laminated layers for cell protection and support.
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smooth ER
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That portion of the endoplasmic reticulum that is free of ribosomes.
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stroma
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Within the chloroplast, the dense fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
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thylakoid
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A flattened membranous sac inside a chloroplast. They exist in an interconnected system in the chloroplast and contain the molecular “machinery” used to convert light energy to chemical energy.
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tight junction
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A type of intercellular junction in animal cells that prevents the leakage of material between cells.
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transmission electron microscope (TEM)
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A microscope that passes an electron beam through very thin sections and is primarily used to study the internal ultrastructure of cells.
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transport vesicle
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A tiny membranous sac in a cell’s cytoplasm carrying molecules produced by the cell.
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vacuole
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A membrane-bounded vesicle whose function varies in different kinds of cells.
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vesicle
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A sac made of membrane in the cytoplasm.
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