A Tour Of The Cell [Ch.6]

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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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Organelles

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Any of several membrane-enclosed structure with specialized functions, suspended in the cytosol of eukaryotic cells.

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Electron Microscope (EM)

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A microscope that used 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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Scanning Electron Microscope (SEM)

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A microscope that used an electron beam to scan the surface of a sample to study details of its topography.

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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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Cell Fractionation

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The disruption of a cell and separation of its parts by centrifugation.

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Cytosol

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The semi fluid portion of the cytoplasm.

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Eukaryotic Cell

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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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Prokaryotic Cell

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A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with prokaryotic cells (bacteria,archaea) are called prokaryotes.

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Nucleoid

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An irregularly-shaped region within the cell of a prokaryote that contains all or most of the genetic material.

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Cytoplasm

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The material or protoplasm within a living cell, excluding the nucleus.

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Plasma Membrane

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A microscopic membrane of lipids and proteins that forms the external boundary of the cytoplasm of a cell or encloses a vacuole, and that regulates the passage of molecules in and out of the cytoplasm.

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Nucleus

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The central and most important part of an object, movement, or group, forming the basis for its activity and growth.

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Nuclear Envelope

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Known as the nuclear envelope, nucleolemma or karyotheca, is the double lipid bilayer membrane which surrounds the genetic material and nucleolus in eukaryotic cells.

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Nuclear Lamina

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A dense (~30 to 100 nm thick) fibrillar network inside the nucleus of a eukaryotic cell. It is composed of intermediate filaments and membrane associated proteins.

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Chromosomes

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A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

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Chromatin

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The material of which the chromosomes of organisms other than bacteria (i.e., eukaryotes) are composed. It consists of protein, RNA, and DNA.

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Nucleolus

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A small dense spherical structure in the nucleus of a cell during interphase.

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Ribosomes

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A minute particle consisting of RNA and associated proteins, found in large numbers in the cytoplasm of living cells. They bind messenger RNA and transfer RNA to synthesize polypeptides and proteins.

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Endomembrane system

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The different membranes that are suspended in the cytoplasm within a eukaryotic cell. These membranes divide the cell into functional and structural compartments, or organelles.

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Vesicles

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A fluid- or air-filled cavity or sac, in particular.

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Endoplasmic Reticulum (ER)

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A network of membranous tubules in the cytoplasm of a cell; involved in the production of phospholipids, proteins, and other functions.

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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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Rough ER

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That portion of the endoplasmic reticulum studded with ribosomes.

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Glycoproteins

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Any of a class of proteins that have carbohydrate groups attached to the polypeptide chain. Also called glycopeptide.

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Transport Vesicles

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A tiny membranous sac in a cells's cytoplasm carrying molecules produced by the cell.

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Golgi Apparatus

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A complex of vesicles and folded membranes within the cytoplasm of most eukaryotic cells, involved in secretion and intracellular transport.

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Lysosome

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An organelle in the cytoplasm of eukaryotic cells containing degradative enzymes enclosed in a membrane.

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Phagocytosis

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The ingestion of bacteria or other material by phagocytes and ameboid protozoans

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Food Vacuoles

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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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Contractile Vacuoles

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A membranous sac that helps move excess water of of certain fresh water protists.

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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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Mitochondria

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An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur. It has a double membrane, the inner layer being folded inward to form layers (cristae).

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Chloroplasts

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(in green plant cells) A plastid that contains chlorophyll and in which photosynthesis takes place.

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Peroxisome

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A small organelle that is present in the cytoplasm of many cells and that contains the reducing enzyme catalase and usually some oxidases.

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Cristae

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Each of the partial partitions in a mitochondrion formed by infolding of the inner membrane.

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Mitochondrial Matrix

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The compartment o the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle.

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Plastids

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Any of a class of small organelles, such as chloroplasts, in the cytoplasm of plant cells, containing pigment or food.

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Thylakoids

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Each of a number of flattened sacs inside a chloroplast, bounded by pigmented membranes on which the light reactions of photosynthesis take place, and arranged in stacks or grana.

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Granum

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A stack of membrane-bound thylakoids in the chloroplast. Grana function in the light reactions of photosynthesis.

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Stroma

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A microscopic pore surrounded by guard cells in the epidermis of Leaves and stems that allows gas exchange between the environment and the interior of the plant.

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Cytoskeleton

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A network of mircotubules, microfilaments, and intermediate filaments that branch throughout the cytoplams and serve a variety of mechanical, transport, and signaling functions.

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Motor Proteins

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A protein that interacts with cytoskeletal elements and other cell component, producing movement of the whole cell parts of the cell.

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Microtubules

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A hollow rod composed of tubing proteins that make up part of the cytoskeleton in all eukaryotic cells is found in cilia and flagella.

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Centrosome

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Structure present tin the cytoplasm of animal cells, important during cell division' functions as a micro-tubule- organizing center. a centrosome has two centrioles.

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Centrioles

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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 centrioles.

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Flagella

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A slender threadlike structure, esp. a microscopic whiplike appendage that enables many protozoa, bacteria, spermatozoa, etc., to swim.

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Cilia

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A short cellular appendage containing microtubules. A motile cilium is specialized for locomotion and is formed from a core of nine outer doublet microtubules and two inner single microtubules unsheathed in an extrension of the plasm membrane. A primary cilium is usually nonmotile and play a sensory and signaling role; it lacks the two inner microtubuels.

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Basal Body

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An organelle that forms the base of a flagellum or cilium and that is similar to a centriole in structure and function.

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Dyneins

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In cilia and flagella, a large contractile protein extending from one microtubule doublet to the adjacent double. ATP hydrolysis rive changes in dynein shape that lead to bending of cilia and flagella.

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Microfilaments

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A cable composed of actin proteins tint the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting lone or with myosin to cause cell contraction' also known as an actin filament.

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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 in muscle and other kinds of cells.

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Cortex

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The outer region of cytoplasm in a eukaryotic cell, lying just under the plasm membrane, that has a more gel-like consistency that the inner regions, due to the presence of multiple microfilaments.

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Myosin

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A type of protein filament that acts as a motor protein with acting filaments to cause cell contraction.

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Pseudopodia

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A temporary protrusion of the surface of an ameboid cell for movement and feeding.

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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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Intermediate Filaments

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A component of the cytoskeleton that include filaments intermediate in size between microtubules and microfilaments.

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Cell Wall

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A protective layer external to the plasm membrane in the cells of plants, prokaryotes, fungi, and some protists. polysaccharides such as cellulose, chitin, and peptidoglycan are an important structural component of cell walls.

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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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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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Secondary Cell Wall

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In plants, a strong and durable a matrix often deposited in several laminated layers for cell protection and support.

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Extracellular Matrix (ECM)

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The substance in which animal cells are embedded, consisting of protein and polysaccharids synthesized and secreted by cells.

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Collagen

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A glycoprotein in the extracellular matrix of animal cells that forms strong fivers, found extensively in connective tissue and bone the most abundant protein in the animal kindgom.

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Proteoglycans

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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. a proteoglycan may consist of up to 95% carbohydrate.

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Fibronectin

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A glycoprotein that helps animal cells attach to the extracellular matrix.

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Intergrins

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In animal cells, a transmembrane receptor protein that interconnects the extracellular matrix and the cytoskeleton.