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35 terms

AP Bio- CH.7

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selective permability
shown by the plasma membrane; allows some substances to cross it more easily than others
amphipathic
describes a phospholipid, meaning it has both a hydrophilic region and hydrophobic region
fluid mosaic model
this states the membrane is a fluid structure with a mosaic of various proteins embedded in or attached to a bilayer of phospholipids
integral protein
typically a transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on either side of the membrane
peripheral protein
a protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer
glycolipid
a lipid with covalently attached carbohydrates
glycoprotein
a protein with one or more carbohydrates attached to it
transport protein
a transmembrane protein that helps a certain substance or class of closely related susbtances cross the membrane
aquaporin
a channel protein in the plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis
osmosis
the diffusion of water into a cell membrane
diffusion
the spontaneous movement of a substance down its concentration gradient, from a region where it is more concentrated to a less concentrated area
concentration gradient
a region along which the density of a chemical susbtance increases or decreases
passive transport
the diffusion of a substance across a biological membrane with no expenditure of energy
hypotonic
referring to a solution that, when surrounded by a cell, will cause the cell to take in water
hypertonic
referring to a solution that, when surrounded by a cell, will cause the cell to lose water
isotonic
referring to a solution that, when surrounded by a cell, has no effect on the passage of water into or out of the cell
osmoregulation
regulation of solute concentrations and water balanced by a cell
turgid
describes a plant cell that's swollen or distended;happens if the walled cell has a greater solute concentration than its surroundings; results in entry of water
flaccid
limp; lacking in stiffness or firmness in a plant cell wall when surroundings have no tendency for water to enter the cell
plasmolysis
a phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment
facilitated diffusion
the spontaneous passage of molecules or ions across a biological membrane with the assistance of specific transmembrane transport proteins
ion channel
a transmembrane protein channel that allows a specific ion to flow across the membrane down its concentration gradient
gated channel
a transmembrane protein channel that opens or closes in response to a particular stimulus
active transport
the movement of a substance across a cell membrane, with an expenditure of energy, against its concentration or electochemical gradient; mediated by specific transport proteins
sodium-potassium pump
a transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell
membrane potential
the difference in electrical charge(voltage) across a cell's plasma membrane, due to the differential distribution of ions; affects the acitivity of excitable cells and the transmembrane movement of all charged substances
electrochemical gradient
the diffusion gradient of an ion, which is affected by both the concentration difference of the ions across a membrane(a chemical force) and the ion's tendency to move relative to the membrane potential (an electrical force)
electrogenic pump
an ion transport protein that generates voltage across a membrane
proton pump
an active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process
cotransport
the coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient
exocytosis
the cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane
phagocytosis
a type of endocytosis in which large particulate substances are taken up by a cell; carried out by some protists and by certain immune cells of animals
pinocytosis
a type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes
receptor-mediated endocytosis
the movement of specific molecules into a cell by the inward budding of membrane vesicles containing proteins with receptor sites specific to the molecules being take in; enables a cell to aquire bulk quantities of specific substances
ligand
a molecule that binds specifically to another molecule, usually a larger one