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Chapter 6 Terms
Cell Structure
64
Biology
Undergraduate 1
02/03/2010

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Term
Organelle
(ōr-guh-nel′)
Definition
Any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells.
Term
cell fractionation
Definition
The disruption of a cell and separation of its parts by centrifugation
Term
prokaryotic cell
(prō′-kār′-ē-ot′-ik)
Definition
A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles.
Term
nucleoid
Definition
A dense region of DNA in a prokaryotic cell.
Term
cytoplasm
Definition
The contents of the cell, exclusive of the nucleus and bounded by the plasma membrane.
Term
Cytosol
(sī′-tō-sol)
Definition
The semifluid portion of the cytoplasm.
Term
eukaryotic cell
(yū′-ker-ē-ot′-ik)
Definition
A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles.
Term
plasma membrane
Definition
The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell’s chemical composition.
Term
Chromosome
(krō′-muh-sōm)
Definition
A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells.
Term
Chromatin
(krō′-muh-tin)
Definition
The complex of DNA and proteins that makes up a eukaryotic chromosome.
Term
Nucleolus
(nū-klē′-ō-lus)
Definition
A specialized structure in the nucleus, consisting of chromatin regions containing ribosomal RNA genes along with ribosomal proteins imported from the cytoplasmic site of rRNA synthesis and ribosomal subunit assembly.
Term
nucleus
Definition
(1)An atom’s central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons.
Term
nuclear envelope
Definition
The double membrane in a eukaryotic cell that encloses the nucleus, separating it from the cytoplasm.
Term
Ribosome
(rī′-buh-sōm′)
Definition
A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus.
Term
nuclear lamina
Definition
A netlike array of protein filaments lining the inner surface of the nuclear envelope; it helps maintain the shape of the nucleus.
Term
endoplasmic reticulum (ER)
(en′-dō-plaz′-mik ruh-tik′-yū-lum)
Definition
An extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.
Term
smooth ER
Definition
That portion of the endoplasmic reticulum that is free of ribosomes.
Term
rough ER
Definition
That portion of the endoplasmic reticulum studded with ribosomes.
Term
endomembrane system
Definition
The collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles; includes the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles.
Term
Vesicle
(ves′-i-kul)
Definition
A sac made of membrane in the cytoplasm.
Term
glycoprotein
Definition
A protein with one or more carbohydrates covalently attached to it.
Term
transport vesicle
Definition
A tiny membranous sac in a cell’s cytoplasm carrying molecules produced by the cell.
Term
Golgi apparatus
(gol′-jē)
Definition
An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncellulose carbohydrates.
Term
Phagocytosis
(fag′-ō-sī-tō′-sis)
Definition
A type of endocytosis in which large particulate substances are taken up by a cell. It is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells).
Term
Lysosome
(lī′-suh-sōm)
Definition
A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists.
Term
food vacuole
Definition
A membranous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell.
Term
contractile vacuole
Definition
A membranous sac that helps move excess water out of certain freshwater protists.
Term
central vacuole
Definition
A membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development.
Term
Mitochondrion
(mī′-tō-kon′-drē-un) (plural, mitochondria)
Definition
An organelle in eukaryotic cells that serves as the site of cellular respiration.
Term
Chloroplast
(klōr′-ō-plast)
Definition
An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
Term
Peroxisome
(puh-rok′-suh-sōm′)
Definition
An organelle containing enzymes that transfer hydrogen (H2) from various substrates to oxygen (O2), producing and then degrading hydrogen peroxide (H2O2).
Term
Crista
(plural, cristae) (kris′-tuh, kris′-tē)
Definition
An infolding of the inner membrane of a mitochondrion that houses electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP (ATP synthase).
Term
mitochondrial matrix
Definition
The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle.
Term
Thylakoid
(thī′-luh-koyd)
Definition
A flattened membranous sac inside a chloroplast which exist in an interconnected system in the chloroplast and contain the molecular “machinery” used to convert light energy to chemical energy.
Term
Granum
(gran′-um) (plural, grana)
Definition
A stack of membrane-bounded thylakoids in the chloroplast which function in the light reactions of photosynthesis.
Term
Stroma
(strō′-muh)
Definition
Within the chloroplast, the dense fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
Term
mitochondrial matrix
Definition
The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle.
Term
plastid
Definition
One of a family of closely related organelles that includes chloroplasts, chromoplasts, and amyloplasts (leucoplasts), which are found in cells of photosynthetic organisms.
Term
cytoskeleton
Definition
A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions.
Term
motor protein
Definition
A protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell.
Term
microtubule
Definition
A hollow rod composed of tubulin proteins that make up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella.
Term
Centrosome
(sen′-trō-sōm)
Definition
Structure present in the cytoplasm of animal cells, important during cell division; functions as a microtubule-organizing center.
Term
Centriole
(sen′-trē-ōl)
Definition
A structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a 9 + 0 pattern.
Term
Flagellum
(fluh-jel′-um) (plural, flagella)
Definition
A long cellular appendage specialized for locomotion.
Term
Cilium
(sil′-ē-um) (plural, cilia)
Definition
A short cellular appendage containing microtubules.
Term
basal body (bā′-sul)
Definition
A eukaryotic cell structure consisting of a 9 + 0 arrangement of microtubule triplets.
Term
Dynein
(dī′-nē-un)
Definition
In cilia and flagella, a large contractile protein extending from one microtubule doublet to the adjacent doublet.
Term
microfilament
Definition
A cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction; also known as an actin filament.
Term
Actin (ak′-tin)
Definition
A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other kinds of cells.
Term
cortex
Definition
(1)The outer region of cytoplasm in a eukaryotic cell, lying just under the plasma membrane, that has a more gel-like consistency than the inner regions, due to the presence of multiple microfilaments. (2) In plants, ground tissue that is between the vascular tissue and dermal tissue in a root or eudicot stem.
Term
Myosin (mī′-uh-sin)
Definition
A type of protein filament that acts as a motor protein with actin filaments to cause cell contraction.
Term
Pseudopodium
(sū′-dō-pō′-dē-um) (plural, pseudopodia)
Definition
A cellular extension of amoeboid cells used in moving and feeding.
Term
cytoplasmic streaming
Definition
A circular flow of cytoplasm, involving myosin and actin filaments, that speeds the distribution of materials within cells.
Term
intermediate filament
Definition
A component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments.
Term
cell wall
Definition
A protective layer external to the plasma membrane in the cells of plants, prokaryotes, fungi, and some protists.
Term
primary cell wall
Definition
In plants, a relatively thin and flexible layer first secreted by a young cell.
Term
middle lamella
(luh-mel′-uh)
Definition
In plants, a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young cells.
Term
secondary cell wall
Definition
In plants, a strong and durable matrix often deposited in several laminated layers for cell protection and support.
Term
extracellular matrix (ECM)
Definition
The substance in which animal cells are embedded, consisting of protein and polysaccharides synthesized and secreted by cells.
Term
collagen
Definition
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.
Term
Proteoglycan
(prō′-tē-ō-glī′-kan)
Definition
A glycoprotein consisting of a small core protein with many carbohydrate chains attached, found in the extracellular matrix of animal cells.
Term
fibronectin
Definition
A glycoprotein that helps animal cells attach to the extracellular matrix.
Term
integrin
Definition
In animal cells, a transmembrane receptor protein that interconnects the extracellular matrix and the cytoskeleton.
Term
Plasmodesma
(plaz′-mō-dez′-muh) (plural, plasmodesmata)
Definition
An open channel in the cell wall of a plant through which strands of cytosol connect from an adjacent cell.
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