Glossary of Chapter 7 - A Tour of the Cell

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Light microscope
the first microscopes used by Renaissance scientists, use light and lenses to magnify the image of the specimen; light is refracted to magnify the image
Resolving power
a measure of the clarity of the image; the minimum distance two points can be separated and still be distinguished as two separate points
subcellular structures
Electron microscope
a form of microscopy in which a beam of electrons are passed through the specimen
Transmission electron microscope
used predominantly to study the internal ultrastructure of cells; focus a beam of electrons, using electromagnets, through a small portion of the specimen
Scanning electron microscope
useful for detailed study of the surface of the specimen; great depth of field results in an image that appears three-dimensional
Cell fractionation
to take cells apart, separating the major organelles so that their functions can be studied
powerful centrifuges that can spin the solution at speeds of up to 80,000 revolutions per minute
Prokaryotic cell
cells that lack a defined nucleus and many important internal cellular structures
a region inside prokaryotic cells where the genetic material is concentrated, not bound by a membrane
the entire region from the nuclear membrane (in eukaryotic cells) to the cellular membrane; internal body of the cell
semi-fluid medium that composes the cytoplasm
Plasma membrane
the outer boundary of a cell; functions as a selective barrier that allows sufficient passage of oxygen, nutrients, and wasters to service the entire volume of the cell
contains most of the genes that control the eukaryotic cell; generally the most conspicuous organelle inside a eukaryotic cell
Nuclear lamina
a netlike array of protein filaments that maintains the shape of the nucleus
material inside the nucleus which is composed of the genetic material, DNA, etc; appears through a light microscope as a diffuse mass
when cell prepares to divide, chromatin condenses enough to be discerned as separate structures called chromosomes; each species has a characteristic number of chromosomes (humans have 46)
a prominent structure within the nondividing nucleus where components of ribosomes are synthesized and assembled
the sight where cells make proteins; cells with high rates of protein synthesis have a large number of ribosomes; free ribosomes are suspended in the cytosol; bound ribosomes are attached to the outside of the endoplasmic reticulum
Endomembrane system
a system made up of many different membranes that are related either through direct physical continuity or as the transfer of membrane segments as tiny vesicles; includes the nuclear envelope, endoplasmic reticulum, Gogli apparatus, lysosomes, various kinds of vacuoles, and the plasma membrane; thickness, molecular composition, and metabolic behavior of a membrane can change over time
Endoplasmic reticulum
an extensive labyrinth of membranes consisting of a network of membranous tubule and sacs called cisternae
Smooth ER
portion of the ER that lacks ribosomes on its cytoplasmic surface; functions in diverse metabolic processes such as production of lipids & steroids, metabolism of carbohydrates, and detoxification of drugs and poisons
Rough ER
portion of the ER that is studded with ribosomes on its cytoplasmic surface; confluent with the nuclear membrane which is also studded with ribosomes; involved mainly with the composition of secretory proteins and membranes
proteins that are covalently bonded to carbohydrates
Transport vesicles
vesicles that are in transit from one part of the cell to another that transport cellular products
Golgi apparatus
the cellular center of manufacturing warehousing, sorting, and shipping; extensive in cells that specialize in secretion; consists of flattened membranous sacs – or cisternae; vesicles transfer materials from the Golgi to other structures
a membrane-bounded sac of hydrolytic enzymes that the cell uses to digest macromolecules; maintains an acidic pH by pumping H+ ions in from the cytosol so that the enzymes can work most efficiently
enzymatic hydrolysis occurs in many cases, one is when one cell engulfs another smaller organism or food particle and digests it
Food vacuoles
large, membrane bound sacs formed by phagocytosis
Contractile vacuoles
used by many protests, etc. to pump excess water from the cell
Central vacuole
mature plant cells generally contain this large central vacuole used to store excess organic and inorganic molecules
membrane that surrounds the central vacuole in plant cells
the sites of cellular respiration in eukaryotic cells
the sites of photosynthesis in plant cells and among some single celled algae
convoluted infoldings of the inner membrane in a mitochondrion; encloses the mitochondrial matrix; gives the inner membrane a large surface area that enhances productivity of cellular respiration
Mitochondrial matrix
enclosed by the mitochondrial matrix; some steps of cellular respiration occur here; concentrated with many enzymes
a specialized metabolic compartment bounded by a single membrane; contain enzymes that transfer hydrogen from various substrates to oxygen, producing H2O2(toxic) but also contains enzymes to convert hydrogen peroxide into water; serve diverse functions
a network of fibers extending throughout the cytoplasm; plays a major role in organizing the structure and activities of the cell; give mechanical support to the cell and maintain its shape
thickest of the fibers that make up the cytoskeleton; found in the cytoplasm of all eukaryotic cells; composed of tubulin; involved in the movement of chromosomes during cell division
also called actin filaments; the thinnest filaments that make up the cytoskeleton
Intermediate filaments
fibers in the cytoskeleton that lie between microtubules and microfilaments in size
a region near the nucleus from which microtubules grow out
centrioles are composed of nine sets of triplet molecules; a pair of centrioles is located within the centrosome of an animal cell
locomotive appendages that protrude from some cells; usually limited to one or a few per cell
locomotive appendages that protrude from some cells; usually occur in large numbers across the cell surface
Basal body
structure that anchors the microtubule assembly within a flagella or cilia in the cell; structurally identical to a centriole
a motor molecule (protein) that connects microtubule doublets together in a cilia or flagella; responsible for the beating motion of the cellular extension; undergoes a series of movements caused by changes in the conformation of the protein powered by ATP
a globular protein which composes microfilaments in the cytoskeleton
a protein that is prevalent in muscle cells, functions as a motor molecule, it is found in an alternating pattern with actin; allows the muscle cells to shorten
an ameboid cell crawls along a surface by extending and flowing into this cellular extension; composed of actin-myosin fibers; white blood cells in humans move by crawling
Cytoplasmic streaming
a circular flow of cytoplasm within plant cells; speeds the distribution of materials within cells
Cell wall
a distinguishing feature of plant cells; protects the plant cell, maintains its shape, and prevents excessive uptake of water
Extracellular matrix
composed predominantly of glycoproteins that are secreted by the cells
the most abundant glycoprotein found in the ECM; forms strong fibers outside cells
glycoproteins composed primarily of carbohydrates and can be found in large complexes
bind to the receptor proteins called integrins
receptor proteins that are built into the plasma membrane; located expansively across the membrane and bind to the cytoskeleton on the interior of the cell; help to integrate changes that occur inside and outside the cell
channels located through and between the cell walls of plants that allow communication and transport directly between cells
Tight junctions
intercellular junctions that form continuous belts around the cell; fuses cells together, often to prevent fluid leakage across a layer of epithelial cells; i.e. found between intestinal epithelial cells
form anchoring “rivets” between cells, resulting in strong epithelial sheets; reinforced by intermediate filaments made of the sturdy protein keratin
Gap junctions
gaps that provide cytoplasmic channels between adjacent cells; large of enough for small molecules to pass through; especially important in animal embryos

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