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BIOL 114

Ch 4: Tour of the Cell

TermDefinition
cell junction A structure that connects animal cells to one another in a tissue.
cell theory The theory that all living things are composed of cells and that all cells come from other cells.
central vacuole A membrane-enclosed sac occupying most of the interior of a mature plant cell, having diverse roles in reproduction, growth, and development.
Chloroplasts An organelle found in plants and photosynthetic protists. Enclosed by two concentric membranes, a chloroplast absorbs sunlight and uses it to power the synthesis of organic food molecules (sugars).
chromatin The combination of DNA and proteins that constitutes chromosomes; often used to refer to the diffuse, very extended form taken by the chromosomes when a eukaryotic cell is not dividing.
chromosome A gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of a prokaryotic cell. Each chromosome consists of one very long threadlike DNA molecule and associated proteins. See also chromatin.
cilium (plural, cilia) A short appendage that propels some protists through the water and moves fluids across the surface of many tissue cells in animals.
cristae (plural, cristae) A fold of the inner membrane of a mitochondrion. Enzyme molecules embedded in cristae make ATP.
cytoplasm Everything inside a eukaryotic cell between the plasma membrane and the nucleus; consists of a semifluid medium and organelles; can also refer to the interior of a prokaryotic cell.
cytoskeleton A meshwork of fine fibers in the cytoplasm of a eukaryotic cell; includes microfilaments, intermediate filaments, and microtubules.
electron microscope (EM) An instrument that focuses an electron beam through or onto the surface of a specimen. An electron microscope achieves a thousandfold greater resolving power than a light microscope; the most powerful EM can distinguish objects as small as 0.2 nm (2 × 10-10 m).
endomembrane system A network of organelles that partitions the cytoplasm of eukaryotic cells into functional compartments. Some of the organelles are structurally connected to each other, whereas others are structurally separate but functionally connected by the traffic of vesicles between them.
endoplasmic reticulum (ER) An extensive membranous network in a eukaryotic cell, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions. See also rough ER; smooth ER.
eukaryotic cells A type of cell that has a membrane-enclosed nucleus and other membrane-enclosed organelles. All organisms except bacteria and archaea are composed of eukaryotic cells.
extracellular matrix A substance in which the cells of an animal tissue are embedded; consists of protein and polysaccharides.
flagellum (plural, flagella) A long appendage that propels protists through the water and moves fluids across the surface of many tissue cells in animals. A cell may have one or more flagella.
fluid mosaic A description of membrane structure, depicting a cellular membrane as a mosaic of diverse protein molecules embedded in a fluid bilayer made of phospholipid molecules.
food vacuoles (1) A tiny sac in a eukaryotic cell's cytoplasm that engulfs nutrients. (2) The simplest type of digestive compartment.
Golgi apparatus An organelle in eukaryotic cells consisting of stacks of membranous sacs that modify, store, and ship products of the endoplasmic reticulum.
granum (plural, grana) A stack of hollow disks formed of thylakoid membrane in a chloroplast. Grana are the sites where light energy is trapped by chlorophyll and converted to chemical energy during the light reactions of photosynthesis.
light microscope (LM) An optical instrument with lenses that refract (bend) visible light to magnify images and project them into a viewer's eye or onto photographic film.
lysosome A digestive organelle in eukaryotic cells; contains enzymes that digest the cell's food and wastes.
Magnification An increase in the apparent size of an object.
matrix The thick fluid contained within the inner membrane of the mitochondrion.
Microtubule The thickest of the three main kinds of fibers making up the cytoskeleton of a eukaryotic cell; a straight, hollow tube made of globular proteins called tubulins. Microtubules form the basis of the structure and movement of cilia and flagella.
mitochondrion (plural, mitochondria) An organelle in eukaryotic cells where cellular respiration occurs. Enclosed by two concentric membranes, it is where most of the cell's ATP is made.
nuclear envelope A double membrane, perforated with pores, that encloses the nucleus and separates it from the rest of the eukaryotic cell.
nucleolus A structure within the nucleus of a eukaryotic cell where ribosomal RNA is made and assembled with proteins to make ribosomal subunits; consists of parts of the chromatin DNA, RNA transcribed from the DNA, and proteins imported from the cytoplasm.
Organelle A membrane-enclosed structure with a specialized function within a eukaryotic cell.
Phospholipid A molecule that is a constituent of the inner bilayer of biological membranes, having a hydrophilic head and a hydrophobic tail.
phospholipid bilayer A double layer of phospholipid molecules (each molecule consisting of a phosphate group bonded to two fatty acids) that is the primary component of all cellular membranes.
plasma membrane The thin layer of lipids and proteins that sets a cell off from its surroundings and acts as a selective barrier to the passage of ions and molecules into and out of the cell; consists of a phospholipid bilayer in which proteins are embedded.
Prokaryotic cell A type of cell lacking a nucleus and other organelles; found only in the domains Bacteria and Archaea.
resolving power A measure of the clarity of an image; the ability of an optical instrument to show two objects as separate.
ribosomes A cellular structure consisting of RNA and protein organized into two subunits and functioning as the site of protein synthesis in the cytoplasm. The ribosomal subunits are constructed in the nucleolus.
rough ER (rough endoplasmic reticulum) A network of interconnected membranous sacs in a eukaryotic cell's cytoplasm. Rough ER membranes are studded with ribosomes that make membrane proteins and secretory proteins. The rough ER constructs membrane from phospholipids and proteins.
scanning electron microscope (SEM) A microscope that uses an electron beam to study the surface architecture of a cell or other specimen.
smooth ER (smooth endoplasmic reticulum) A network of interconnected membranous tubules in a eukaryotic cell's cytoplasm. Smooth ER lacks ribosomes. Enzymes embedded in the smooth ER membrane function in the synthesis of certain kinds of molecules, such as lipids.
stroma A thick fluid enclosed by the inner membrane of a chloroplast. Sugars are made in the stroma by the enzymes of the Calvin cycle.
transmission electron microscope (TEM) A microscope that uses an electron beam to study the internal structure of thinly sectioned specimens.
transport vesicles A tiny membranous sphere in a cell's cytoplasm carrying molecules produced by the cell. The vesicle buds from the endoplasmic reticulum or Golgi apparatus and eventually fuses with another organelle or the plasma membrane, releasing its contents.
vacuoles A membrane-enclosed sac, part of the endomembrane system of a eukaryotic cell, having diverse functions.
Created by: EdL