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42 Cards in this Set

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Chapter 4
Glossary
BASAL BODY
A centriole that, after giving rise to microtubules of a flagellum or cilium, remains attached to its base in the cytoplasm.
CELL
[L. cella, small room] Smallest living unit; organized unit with a capacity to survive and reproduce on its own given DNA instructions, energy sources, and raw materials.
CELL JUNCTION
Site where cells are interacting physically, functionally, or both.
CELL THEORY
All organisms consist of one or more cells, the smallest units with a capacity for independent life that no longer spontaneously arise under existing conditions on Earth.
CELL WALL
A semirigid, permeable structure external to the plasma membrane; helps many cells retain their shape and resist rupturing.
CENTRAL VACUOLE
Fluid-filled storage organelle of plant cell; its growth enhances cell surface area.
CENTRIOLE
Structure that gives rise to microtubules of cilia and flagella.
CHLOROPLAST
The organelle of photosynthesis in plants and many protistans.
CHROMATID
Of a duplicated eukaryotic chromosome, one of two DNA molecules (with associated proteins) attached to each other at the centromere.
CHROMATIN
A cell's collection of DNA and all of the proteins associated with it.
CHROMOSOME
[Gk. chroma, color, + soma, body] Of eukaryotic cells, a DNA molecule, duplicated or unduplicated, with many associated proteins. Of prokaryotic cells, a circular DNA molecule.
CILIUM
plural cilia. Short motile or sensory structure of certain eukaryotic cells; its core is a 9 + 2 array of microtubules.
CYTOMEMBRANE SYSTEM
Organelles (ER & Golgi bodies) that modify, package, and distribute new protein and lipids; also various vesicles (e.g., lysosomes) that have diverse functions.
CYTOPLASM
All cell parts, particles, and semifluid substances between the plasma membrane and nucleus or nucleoid.
CYTOSKELETON
Dynamic internal framework that structurally supports eukaryotic cells and organizes and moves a cell and its structures.
ENDOPLASMIC RETICULUM (OR ER)
Organelle that starts at nucleus and curves through cytoplasm. New polypeptides get side chains in rough ER (has ribosomes on its cytoplasmic side); smooth ER (has no ribosomes) is a site of lipid synthesis.
EUKARYOTIC CELL
[Gk. eu, good, + karyon, kernel] Cell having a nucleus and other membrane-bound organelles.
FLAGELLUM
plural flagella. A motile structure of many free-living eukaryotic cells. Its core has a 9 + 2 array of microtubules. Typically longer than cilia.
FLUID MOSAIC MODEL
A cell membrane consists of a lipid bilayer and proteins. Its lipids are mainly structural; they make it impermeable to water-soluble molecules, yet (by packing variations and movements), impart fluidity. Its diverse proteins perform most membrane functions (e.g., transport, signal reception).
GOLGI BODY
Organelle of lipid assembly, polypeptide chain modification, and packaging of both in vesicles for export or transport to locations in cytoplasm.
INTERMEDIATE FILAMENT
Cytoskeletal element; mechanically strengthens some animal cells.
LYSOSOME
Important organelle of intracellular digestion.
MICROFILAMENT
[Gk. mikros, small, + L. filum, thread] Two thin, twisted polypeptide chains; cytoskeletal element that helps cell move, and helps produce and maintain cell shapes.
MICROGRAPH
Photograph of an image that came into view with the aid of a microscope.
MICROTUBULAR SPINDLE
Bipolar array of many microtubules; forms during nuclear division and moves chromosomes apart in controlled ways.
MICROTUBULE
Cylinder of tubulin subunits; cytoskeletal element with roles in cell shape, growth, and motion (e.g., part of cilia, flagella, and spindle apparatus).
MITOCHONDRION
Double-membrane organelle of ATP formation. Only site of aerobic respiration's second and third stages. May have endosymbiotic origins.
NUCLEAR ENVELOPE
Outermost portion of a cell nucleus; composed of a double membrane (two lipid bilayers and associated proteins).
NUCLEOLUS
[L. nucleolus, tiny kernel] In a nondividing cell nucleus, a site for assembling protein and RNA subunits that will later join up as ribosomes in the cytoplasm.
NUCLEUS
[L. nucleus, a kernel] Of atoms, a central core of one or more protons and (in all but hydrogen atoms) neutrons. In a eukaryotic cell, the organelle that physically separates DNA from cytoplasmic machinery.
ORGANELLE
Membrane-bound sac or compartment in the cytoplasm having one or more specialized metabolic functions. Most eukaryotic cells have a profusion of them.
PEROXISOME
Vesicle in which fatty acids and amino acids are first digested to hydrogen peroxide and then converted to harmless products.
PHOSPHOLIPID
Organic compound that has a glycerol backbone, two fatty acid tails, and a hydrophilic head of two polar groups (one being phosphate). Phospholipids are the main structural component of cell membranes.
PLASMA MEMBRANE
Outermost cell membrane; structural and functional boundary between cytoplasm and the fluid outside the cell.
PLASMODESMA
plural plasmodesmata. Plant cell junction; a channel that connects the cytoplasm of adjoining cells.
PROKARYOTIC CELL
[L. pro, before, + Gk. karyon, kernel] Archaebacterium or eubacterium; single-celled organism, most often walled; lacks the profusion of membrane-bound organelles observed in eukaryotic cells.
PSEUDOPOD
A dynamically extending lobe of cytoplasm used for motility or engulfment.
RIBOSOME
Two subunits of rRNA and proteins briefly joined together as a structure on which mRNA is translated into polypeptide chains.
SURFACE-TO-VOLUME RATIO
Mathematical relation in which volume increases with the cube of the diameter, but surface area increases only with the square. The volume of a cell expanding in diameter only would increase faster than the surface area of the plasma membrane servicing it; a major constraint on cell size and shape.
VESICLE
[L. vesicula, little bladder] One of various small, membrane-bound sacs in cytoplasm that function in the transport, storage, or digestion of substances.
WAVELENGTH
A wavelike form of energy in motion. The horizontal distance between the crests of every two successive waves.