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AP Biology
Cell Structure and Function
33
Biology
12th Grade
05/03/2011

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Term
Cell
Definition
smallest unit with the properties of life: a capacity for metabolism, controlled responses to the environment, growth, and reproduction
Term
Plasma membrane
Definition
outer cell membrane; the structural and functional boundary between cytoplasm and extracellular fluid
Term
Nucleus
Definition
large organelle with an outer envelope of two pore-ridden lipid bilayers that separates eukaryotic chromosomes from the cytoplasm
Term
Nucleoid
Definition
the portion of a prokaryotic cell where DNA is physically organized but not enclosed in a membrane
Term
Cytoplasm
Definition
all cell parts, particles, and semifluid substances between the plasma membrane and the nucleus or nucleoid
Term
Lipid Bilayer
Definition
structural basis of all cell membranes; mainly phospholipids arranged tail-to-tail in two layers, with hydrophilic heads of one dissolved in cytoplasmic fluid and the heads of the other in extracellular fluid
Term
Ribosomes
Definition
the site of polypeptide chain synthesis in all cells. An intact ribosome has two subunits of rRNA and proteins
Term
Surface-to-volume ratio
Definition
a relationship in which the volume of an object increases with the cube of the diameter, but the surface area increases with the square
Term
Organelles
Definition
physically separate chemical reactions, may of which are incompatible; organize metabolic events
Term
Vesicle
Definition
A small, membrane-bound sac in the cytoplasm; different sacs transport or store substances or hold enzymes that digest their contents
Term
Nuclear Envelope
Definition
a double membrane that is the outer boundary of the nucleus
Term
Nucleolus
Definition
in an interphase nucleus, a mass of material from which RNA and proteins are assembled into the subunits of ribosomes
Term
Endoplasmic reticulum (ER)
Definition
organelle that extends from the nuclear envelope through cytoplasm. Ribosomes coat the cytoplasmic side of rough ER, which modifies many new polypeptide chains in its lumen. Membrane lipids are assembled, fatty acids are broken down, and some toxins are inactivated in the lumen of smooth ER
Term
Golgi bodies
Definition
site of final modification of proteins, lipids; sorting and packaging them for used inside cell or for export
Term
Lysosome
Definition
vesicle filled with enzymes that functions in intracellular digestion
Term
Peroxisome
Definition
enzyme-filled vesicle that breaks down amino acids, fatty acids, and toxic substances such as ethanol
Term
Mitochondrion
Definition
double-membraned organelle of ATP formation; only site of the second and third stages of aerobic respiration
Term
Chloroplast
Definition
organelle of photosynthesis in plants and algae. Two outer membranes enclose a semifluid interior, the stroma. A third membrane forms a compartment inside that functions in ATP and NADPH formation; sugars form in the stroma
Term
Central Vacuole
Definition
in many mature, living plant cells, an organelle that stores amino acids, sugars, and some wastes; when it enlarges during growth, it forces the cell to enlarge and increase its surface area
Term
Cell wall
Definition
of many cells (not animal cells) a semirigid but permeable structure that surrounds the plasma membrane; helps a cell retain its shape and resist rupturing
Term
Primary wall
Definition
the first thin, pliable wall of young plant cells
Term
Secondary wall
Definition
a rigid, permeable wall inside the primary wall of many plant cells; forms after the first growing season
Term
Cell junction
Definition
of a tissue, any molecular structure that connects adjoining cells physically, chemically, or both at their plasma membranes
Term
Cytoskeleton
Definition
in a eukaryotic cell, the dynamic framework of diverse protein filaments that structurally support, organize, and move the cell and internal structures. Prokaryotic cells have a few similar protein filaments
Term
Microtubule
Definition
largest cytoskeletal element; a filament of tubulin subunits. Contributes to cell shape, growth, and function
Term
Microfilament
Definition
the thinnest cytoskeletal element; consists of actin subunits that function in cell contraction, movement, and structural support
Term
Intermediate Filament
Definition
cytoskeletal element that mechanically strengthens some cells
Term
Cell cortex
Definition
a dynamic mesh of crosslinked cytoskeletal elements just underneath the plasma membrane and attached to it
Term
Flagellum
Definition
of many eukaryotic cells, a long, whip-like motile structure with an inner 9 + 2 array of microtubules. prokaryotic flagella do not have this array and are not whip-like; they rotate like a propeller
Term
Cillium
Definition
a motile structure with a 9 + 2 array of microtubules that projects from the plasma membrane of certain eukaryotic cells. Modified cilia, such as those of hair cells, have sensory functions
Term
Centriole
Definition
a barrel-shaped structure that arises from a centrosome and organizes newly forming microtubules into a 9 + 2 array inside a cillium or flagellum
Term
Basal body
Definition
an organelle that strated out as a centiole, the source of a 9 + 2 array of microtubules in a cillium or flagellum. It remains below the finished array
Term
Pseudopod
Definition
a dynamic lobe of membrane-enclosed cytoplasm; functions in motility and phagocytosis by amoebas, amoeboid cells, and many white blood cells
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