Ch. 6 Biology (The Cell)
Terms
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- actin
- A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells.
- aminopeptidase
- An enzyme found within the small intestine that splits off one amino acid at a time, beginning at the opposite end of the polypeptide containing a free carboxyl group.
- basal body
- A eukaryotic cell organelle consisting of a 9 + 0 arrangement of microtubule triplets; may organize the microtubule assembly of a cilium or flagellum; structurally identical to a centriole.
- cell fractionation
- The disruption of a cell and separation of its organelles by centrifugation.
- cell wall
- A protective layer external to the plasma membrane in plant cells, prokaryotes, fungi, and some protists. In plant cells, the wall is formed of cellulose fibers embedded in a polysaccharide-protein matrix. The primary cell wall is thin and flexible, whereas the secondary cell wall is stronger and more rigid and is the primary constituent of wood.
- central vacuole
- A membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development.
- centriole
- A structure in an animal cell composed of cylinders of microtubule triplets arranged in a 9 + 0 pattern. An animal cell usually has a pair of centrioles involved in cell division.
- centrosome
- Material present in the cytoplasm of all eukaryotic cells, important during cell division; the microtubule-organizing center.
- chloroplast
- An organelle found only in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
- chromatin
- The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, chromatin exists as a mass of very long, thin fibers that are not visible with a light microscope.
- chromosome
- A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins. See chromatin.
- cilium
- A short cellular appendage specialized for locomotion, formed from a core of nine outer doublet microtubules and two inner single microtubules ensheathed in an extension of plasma membrane.
- 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.
- contractile vacuole
- A membranous sac that helps move excess water out of certain cells.
- crista
- (plural, cristae) An infolding of the inner membrane of a mitochondrion that houses the electron transport chain and the enzyme catalyzing the synthesis of ATP.
- cytoplasm
- The entire contents of the cell, exclusive of the nucleus, and bounded by the plasma membrane.
- cytoplasmic streaming
- A circular flow of cytoplasm, involving myosin and actin filaments, that speeds the distribution of materials within cells.
- cytoskeleton
- A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical and transport functions.
- cytosol
- The semifluid portion of the cytoplasm.
- desmosome
- A type of intercellular junction in animal cells that functions as an anchor.
- dynein
- A large contractile protein forming the side-arms of microtubule doublets in cilia and flagella.
- electron microscope (EM)
- A microscope that focuses an electron beam through a specimen, resulting in resolving power a thousandfold greater than that of a light microscope. 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 cell surfaces.
- endomembrane system
- The collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles.
- eukaryotic cell
- 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.
- extracellular matrix (ECM)
- The substance in which animal tissue cells are embedded, consisting of protein and polysaccharides.
- fibronectin
- A glycoprotein that helps cells attach to the extracellular matrix.
- flagellum
- (plural, flagella) A long cellular appendage specialized for locomotion. The flagella of prokaryotes and eukaryotes differ in both structure and function.
- food vacuole
- A membranous sac formed by phagocytosis.
- gap junction
- A type of intercellular junction in animal cells that allows the passage of material or current between cells.
- glycoprotein
- A protein covalently attached to a carbohydrate.
- Golgi apparatus
- An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum.
- granum
- (plural, grana) A stacked portion of the thylakoid membrane in the chloroplast. Grana function in the light reactions of photosynthesis.
- integrin
- A receptor protein built into the plasma membrane that interconnects the extracellular matrix and the cytoskeleton.
- intermediate filament
- A component of the cytoskeleton that includes all filaments intermediate in size between microtubules and microfilaments.
- light microscope (LM)
- An optical instrument with lenses that refract (bend) visible light to magnify images of specimens.
- lysosome
- A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of eukaryotic cells.
- microfilament
- A solid rod of actin protein in the cytoplasm of almost all eukaryotic cells, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction.
- microtubule
- A hollow rod of tubulin protein in the cytoplasm of all eukaryotic cells and in cilia, flagella, and the cytoskeleton.
- middle lamella
- A thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young plant cells.
- mitochondrial matrix
- The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the Krebs cycle.
- mitochondrion
- (plural, mitochondria) An organelle in eukaryotic cells that serves as the site of cellular respiration.
- myosin
- A type of protein filament that interacts with actin filaments to cause cell contraction.
- nuclear envelope
- The membrane in eukaryotes that encloses the nucleus, separating it from the cytoplasm.
- nuclear lamina
- A netlike array of protein filaments that maintains the shape of the nucleus.
- nucleoid
- A dense region of DNA in a prokaryotic cell.
- nucleolus
- (plural, nucleoli) A specialized structure in the nucleus, formed from various chromosomes and active in the synthesis of ribosomes.
- nucleus
- (1) An atom’s central core, containing protons and neutrons. (2) The chromosome-containing organelle of a eukaryotic cell. (3) A cluster of neurons.
- organelle
- One of several formed bodies with specialized functions, suspended in the cytoplasm of eukaryotic cells.
- peroxisome
- A microbody containing enzymes that transfer hydrogen from various substrates to oxygen, producing and then degrading hydrogen peroxide.
- phagocytosis
- A type of endocytosis involving large, particulate substances, accomplished mainly by macrophages, neutrophils, and dendritic cells.
- plasma membrane
- The membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the cell’s chemical composition.
- plasmodesma
- (plural, plasmodesmata) An open channel in the cell wall of a plant through which strands of cytosol connect from an adjacent cell.
- plastid
- One of a family of closely related plant organelles that includes chloroplasts, chromoplasts, and amyloplasts (leucoplasts).
- primary cell wall
- A relatively thin and flexible layer first secreted by a young plant cell.
- prokaryotic cell
- A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with prokaryotic cells (bacteria and archaea) are called prokaryotes.
- proteoglycan
- A glycoprotein in the extracellular matrix of animal cells, rich in carbohydrate.
- pseudopodium
- (plural, pseudopodia) A cellular extension of amoeboid cells used in moving and feeding.
- ribosome
- A cell organelle constructed in the nucleolus and functioning as the site of protein synthesis in the cytoplasm; consists of rRNA and protein molecules, which make up two subunits.
- rough ER
- That portion of the endoplasmic reticulum studded with ribosomes.
- scanning electron microscope (SEM)
- A microscope that uses an electron beam to scan the surface of a sample to study details of its topography.
- secondary cell wall
- A strong and durable matrix often deposited in several laminated layers for plant cell protection and support.
- smooth ER
- That portion of the endoplasmic reticulum that is free of ribosomes.
- stroma
- The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.
- thylakoid
- A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.
- tight junction
- A type of intercellular junction in animal cells that prevents the leakage of material between cells.
- tonoplast
- A membrane that encloses the central vacuole in a plant cell, separating the cytosol from the vacuolar contents, called cell sap; also known as the vacuolar membrane.
- transmission electron microscope (TEM)
- A microscope that passes an electron beam through very thin sections; primarily used to study the internal ultrastructure of cells.
- transport vesicle
- A tiny membranous sac in a cell’s cytoplasm carrying molecules produced by the cell.
- vesicle
- A sac made of membrane inside of cells.