Chapter 7 - A Tour of the Cell
Terms
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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
- Organelles
- 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
- Ultracentrifuges
- 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
- Nucleoid
- a region inside prokaryotic cells where the genetic material is concentrated, not bound by a membrane
- Cytoplasm
- the entire region from the nuclear membrane (in eukaryotic cells) to the cellular membrane; internal body of the cell
- Cytosol
- 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
- Nucleus
- 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
- Chromatin
- material inside the nucleus which is composed of the genetic material, DNA, etc; appears through a light microscope as a diffuse mass
- Chromosomes
- 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)
- Nucleolus
- a prominent structure within the nondividing nucleus where components of ribosomes are synthesized and assembled
- Ribosomes
- 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
- Glycoproteins
- 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
- Lysosome
- 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
- Phagocytosis
- 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
- Tonoplast
- membrane that surrounds the central vacuole in plant cells
- Mitochondria
- the sites of cellular respiration in eukaryotic cells
- Chloroplasts
- the sites of photosynthesis in plant cells and among some single celled algae
- Cristae
- 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
- Peroxisome
- 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
- Cytoskeleton
- 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
- Microtubules
- 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
- Microfilaments
- 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
- Centrosome
- a region near the nucleus from which microtubules grow out
- Centrioles
- centrioles are composed of nine sets of triplet molecules; a pair of centrioles is located within the centrosome of an animal cell
- Flagella
- locomotive appendages that protrude from some cells; usually limited to one or a few per cell
- Cilia
- 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
- Dynein
- 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
- Actin
- a globular protein which composes microfilaments in the cytoskeleton
- Myosin
- 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
- Pseudopodia
- 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
- Collagen
- the most abundant glycoprotein found in the ECM; forms strong fibers outside cells
- Proteoglycans
- glycoproteins composed primarily of carbohydrates and can be found in large complexes
- Fibronectins
- bind to the receptor proteins called integrins
- 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
- Plasmodesmata
- 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
- Desmosomes
- 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