Campbell Biology: Ninth Edition - Chapter 6: A Tour of the Cell

light microscope (LM)

an optical instrument with lenses that refract (bend) visible light to magnify images of specimens

organelle

any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells

electron microscope (EM)

a microscope that uses magnets to focus an electron beam on or through a spectrum, resulting in a practical resolution of a hundredfold greater than that of a light microscope using standard techniques. A transmission electron microscope (TEM) is used to study the internal structure of thin sections of cells. A scanning electron microscope (SEM) is used to study the fine details of the cell surface.

scanning electron microscope (SEM)

a microscope that uses an electron beam to scan the surface of the sample, coated with metal atoms, to study details of its topography.

transmission electron microscope (TEM)

a microscope that passes electron beam through very thin sections stained with metal atoms and is primarily used to study the internal ultrastructure of cells

cell fractionation

the disruption of a cell and separation of its parts by centrifugation at successively higher speeds

cytosol

the contents of the cell bounded by the plasma membrane; in eukaryotes, the portion exclusive of the nucleus

eukaryotic cell

a type of cell with membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with eukaryotic cells (protists, fungi, and animals) are called eukaryotes

prokaryotic cell

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

nucleoid

a non-membrane-bounded region in a prokaryotic cell where the DNA is concentrated

cytoplasm

the contents of the cell bounded by the plasma membrane; in eukaryotes, the portion exclusive of the nucleus

plasma membrane

the membrane at the boundary of every cell that acts as a selective barrier, regulating the cell's chemical composition

nucleus

an atom's central core, containing protons and neutrons; the organelle of a eukaryotic cell that contains the genetic material in the form of chromosomes, made up of chromatin; a cluster of neutrons

nuclear envelope

in a eukaryotic cell, the double membrane that surrounds the nucleus, perforated with pores that regulate traffic with the cytoplasm. The outer membrane is continuous with the endoplasmic reticulum

nuclear lamina

a netlike array of protein filaments that lines the inner surface of the nuclear envelope and helps maintain the shape of the nucleus

chromosome

a cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each chromosome consists of one very long DNA molecule and associated proteins (a bacterial chromosome usually consists of a single circular DNA molecule and associated proteins. It is found in the nucleoid region, which is not membrane bounded.

chromatin

the complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope

nucleolus

a specialized structure in the nucleus, consisting of chromosomal regions containing ribosomal RNA (rRNA) genes along with ribosomal proteins imported from the cytoplasm; site of rRNA synthesis and ribosomal subunit assembly

ribosome

a complex of rRNA and protein molecules that function as a site of protein synthesis in the cytoplasm; consists of a large and small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus

endomembrane system

the collection of membranes inside and surrounding a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles; includes the plasma membrane, the nuclear envelope, the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles, and vacuoles

vesicle

a membranous sac in the cytoplasm of a eukaryotic cell

endoplasmic reticulum (ER)

an extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions

smooth ER

the portion of the ER that is free of ribosomes

rough ER

the portion of the ER with ribosomes attached

glycoprotein

a protein with one or more covalently attached carbohydrates

transport vesicle

a small membranous sac in a eukaryotic cell's cytoplasm carrying molecules produced by the cell

Golgi apparatus

an organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the ER and synthesize some products, notably noncellular carbohydrates

lysosome

a membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists.

phagocytosis

a type of endocytosis in which large particulate substances or small organisms are taken up by a cell. It's carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophilis, and dendritic cells).

vacuole

a membrane-bounded vesicle whose specialized function varies in different kinds of cells

food vacuole

a membranous sac fromed by phagocytosis of microorganisms or particles to be used as food by the cell

contractile vacuole

a membranous sac formed that helps moves excess water out of certain freshwater protists

central vacuole

in a mature plant cell, a large membranous sac with diverse roles in growth, storage, and sequestration of toxic substances

mitochondria

an organelle in eukaryotic cells that serves as the site of cellular respiration; uses oxygen to break down organic molecules and synthesize ATP

chloroplast

an organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide

endosymbiont theory

the theory that mitochondria and plastids, including chloroplasts, originated as prokaryotic cells engulfed by an ancestral eukaryotic cell. The engulfed cell and its host cell then evolved into a single organism

cristae

an infolding of the inner membrane of a mitochondrion. The inner membrane houses electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP (ATP synthase)

mitochondrial matrix

the compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle, as well as ribosomes and DNA

thylakoid

a flattened, membranous sac inside a chloroplast. Often exist in stacks called grana that are interconnected; their membranes contain molecular "machinery" used to convert light energy to chemical energy

granum

a stack of membrane-bounded thylakoids in the chloroplast. Grana function in the light reactions of photosynthesis

stroma

the dense fluid within the chloroplast surrounding the thylakoid membrane and containing ribosomes and DNA; involved in the synthesis of organic molecules from carbon dioxide and water

plastid

one of a family of closely related organelles that includes chloroplasts, chromoplasts, and amlyoplasts. Found in cells of photosynthetic eukaryotes

peroxisome

an organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen (O2), producing and then degrading hydrogen peroxide (H2O2)

cytoskeleton

a network of microtubules, microfilaments, and intermediate filaments that extend throughout the cytoplasm and serve a variety of mechanical, transport, and signaling function.

motor protein

a protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell

microtubules

a hollow rod composed of tubulin proteins that makes up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella

centrosome

a structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division; has 2 centrioles

centriole

a structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a 9+0 pattern

flagella

a long cellular appendage apecialized for locomotion. Like motile cilia, eukaryotic flagella have a core with 9 outer doublet microtubules and 2 inner single mictrotubules (the "9+2" arrangement) ensheathed in an extension of the plasma membrane.

cilia

a short appendage containing microtubules in eukaryotic cells. A motile cillium is specialized for locomotion or moving fluid past the cell; formed from a core of 9 outer doublet microtubules and 2 inner single microtubules (the "9+2" arrangement) ensheathed in an ectension of the plasma membrane. Primary cillium usually nonmotile and plays sensory and signaling role; lack 2 inner microtubules (the "9+0" structure)

basal body

a eukaryotic cell structure consisting of a "9+0" arrangement of microtubule triplets. The basal body may organize the microtubule assembly of a cilium or flagellum and is structurally very similar to a centriole

dynein

in cilia and flagella, a large motor protein extending from 1 microtubule doublet to the adjacent doublet. ATP hydrolysis drives changes in its shape that lead to bending of cilia and flagella

microfilament

a cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskelton and acting alone or with myosin to cause cell contraction; aka actin filament

actin

a globular protein that links into chains, 2 of which twist helically about each other, forming microfilaments (actin filaments) in muscle and other kinds of cells

cortex

outer region of cytoplasm in a eukaryotic cell, lying just under the plasma membrane, that has a more gel-like consistency that the inner regions due to the presence of multiple microfilaments; in plants, ground tissue that is between the vascular tissue and the dermal tissue in a root or eudicot stem

myosin

a type of motor protein that associates into filaments that interact with actin filaments to cause cell contraction

pseudopodia

a cellular extension of amoeboid cells used in moving and feeding

cytoplasmic streaming

a circular flow of cytoplasm, involving interactions of myosin and actin filaments, that speeds the distribution of materials within cells

intermediate filament

a component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments

cell wall

a protective layer external to the plasma membrane in the cells of plants, prokaryotes, fungi and some protists. Polysaccharides such as cellulose (in plants and some protists), chitin (in fungi), and peptidoglycan (in bacteria) are important structural components of them

primary cell wall

the level of protein structure referring to the specific linear sequence of amino acids

middle lamella

in plants, a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young cells

secondary cell wall

regions of repetitive coiling of folding of the polypeptide backbone of a protein due to hydrogen bonding between constituents of the backbone (not the side chains)

extracellular matrix (ECM)

the meshwork surrounding animal cells, consisting of glycoproteins, polysaccharides and proteoglycans synthesized and secreted by the cells

collagen

a glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone; the most abundant protein in the animal kingdom

proteoglycan

a large molecule consisting of a small core protein with many carbohydrate chains attached, found in the extracellular matrix of animal cells' may consist of up to 95% carbohydrate

fibronectin

in an angiosperm, the stalk portion of the stamen, the pollen-producing reproductive organ of a flower

integrin

in animal cells, a transmembrane receptor protein with 2 subunits that interconnects the extracellular matrix and the cytoskelteton

plasmodesmata

an open channel through the cell wall that connects the cytoplasm of adjacent plant cells, allowing water, small solutes, and some larger molecules to pass between the cells

tight junction

a type of intercellular junction between animal cells that prevents the leakage of material through the space between cells

desmosomes

a type of intercellular junction in animal cells that functions as a rivet, fastening cells together

gap junction

a type of intercellular connection in animal cells, consisting of proteins surrounding a pore that allows the passage of materials between cells