KEY+TERMS+Chapter+4


 * **anchoring junctions -** Adhesive junctions that link cells together into tissues.
 * cell junction -** A structure that connects cells within a tissue to one another.
 * cell theory -** The theory that all living things are composed of cells and all cells come from other cells.
 * central vacuole -** A membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development.
 * centriole -** A structure in an animal cell composed of cylinders of microtubule triplets arranged in a 9 + 0 pattern. An animal cell usually has a pair of centrioles involved in cell division.
 * chloroplast -** An organelle found only in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
 * chromosome -** A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins.
 * cytoskeleton -** A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical and transport functions.
 * flagellum -** A long cellular appendage specialized for locomotion, formed from a core of nine outer doublet microtubules and two inner single microtubules, ensheathed in an extension of plasma membrane.
 * golgi apparatus -** An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum.
 * lysosome -** A membrane-enclosed bag of hydrolytic enzymes found in the cytoplasm of eukaryotic cells.
 * mitochondrion -** An organelle in eukaryotic cells that serves as the site of cellular respiration.
 * nuclear envelope -** The membrane in eukaryotes that encloses the nucleus, separating it from the cytoplasm.
 * nucleolus -** A specialized structure in the nucleus, formed from various chromosomes and active in the synthesis of ribosomes.
 * nucleus -** An atom's central core, containing protons and neutrons.The chromosome-containing organelle of a eukaryotic cell. A cluster of neurons.
 * plasma membrane -** The membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the cell's chemical composition.
 * ribosome -** A cell organelle constructed in the nucleolus and functioning as the site of protein synthesis in the cytoplasm; consists of RNA and protein molecules, which make up two subunits.
 * rough ER -** The portion of the endoplasmic reticulum studded with ribosomes.
 * smooth ER -** That portion of the endoplasmic reticulum that is free of ribosomes.
 * tight junction -** A type of intercellular junction in animal cells that prevents the leakage of material between cells.
 * transport vesicle -** A tiny membranous sac in a cell's cytoplasm carrying molecules produced by the cell.
 * vacuole -** A membrane-enclosed sac taking up most of the interior of a mature plant cell and containing a variety of substances important in plant reproduction, growth, and development. ||