CAMPBELL BIOLOGY NINTH EDITION - CHAPTER 7 MEMBRANE STRUCTURE AND FUNCTION
EXAM QUESTIONS ANSWERED CORRECTLY
selective permeability - Answers a property of biological membranes that allows them to
regulate the passage of substances across them
amphipathic - Answers having both a hydrophilic region and a hydrophobic region
fluid mosaic model - Answers the currently accepted model of cell membrane structure, which
envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of
phospholipids.
integral protein - Answers 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 one or both sides of the membrane (or lining
the channel in the case of a channel protein).
peripheral protein - Answers a protein loosely bound to surface of a membrane or to part of an
integral protein and not embedded in the lipid bilayer
glycolipid - Answers a lipid with one or more covalently attached carbohydrates
glycoprotein - Answers a protein with one or more covalently attached carbohydrates
transport protein - Answers a transmembrane protein that helps a certain substance or class of
closely related substances to cross the membrane
aquaporin - Answers a channel protein in the plasma membrane of a plant, animal or
microorganism cell that specifically facilitates osmosis, the diffusion of free water across the
membrane
diffusion - Answers the spontaneous movement of a substance down its concentration or
electrochemical gradient, from a region where it is more concentrated to a region where it is
less concentrated.
concentration gradient - Answers a region along which the density of a chemical substance
increases or decreases.
passive transport - Answers the diffusion of a substance across a biological membrane with no
expenditure of energy
osmosis - Answers the diffusion of free water across a selectively permeable membrane
tonicity - Answers the ability of a solution surrounding a cell to cause that cell to gain or loose
water.
isotonic - Answers referring to a soultion that, when surrounding a cell, causes no net
, movement of water into or out of a cell
hypertonic - Answers referring to a solution that, when surrounding a cell, will cause the cell to
lose water
hypotonic - Answers referring to a solution that, when surrounding a cell, will cause the cell to
take up water.
osmoregulation - Answers regulation of solute concentrations and water balance by a cell or
organism
turgid - Answers swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a
lower water potential then its surroundings, resulting in entry of water.
flaccid - Answers lacking turgor (stiffness or firmness), as in the plant cell in surroundings
where there is a tendency for water to leave the cell. ( A wall cell becomes flaccid if it has a
higher water potential than its surroundings, resulting in the loss of water.)
plasmolysis - Answers 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 - Answers the passage of molecules or ions down their electrochemical
gradient across a biological membrane with the assistance of specific transmembrane
transport proteins, requiring no energy expenditure.
ion channels - Answers a transmembrane protein channel that allows a specific ion to diffuse
across the membrane down its concentration or electrochemical gradient.
gated channels - Answers a transmembrane protein channel that opens or closes in response to
a particular stimulus
active transport - Answers the movement of a substance across a cell membrane against its
concentration gradient, mediated by specific transport proteins and requiring an expenditure of
energy
sodium-potassium pump - Answers a transport protein in the plasma membrane of animal cells
that actively transports sodium out of the cell an potassium into the cell
membrane potential - Answers the difference in electrical charge (voltage) across a cell's
plasma membrane due to the differential distribution of ions. Membrane potential affects the
activity of excitable cells and the transmembrane movement of all charged substances.
electrochemical gradient - Answers the diffusion gradient of an ion, which is affected by both
the concentration difference of an ion across a membrane (a chemical force) and the ion's
tendency to move relative to the membrane potential (an electrical force).
EXAM QUESTIONS ANSWERED CORRECTLY
selective permeability - Answers a property of biological membranes that allows them to
regulate the passage of substances across them
amphipathic - Answers having both a hydrophilic region and a hydrophobic region
fluid mosaic model - Answers the currently accepted model of cell membrane structure, which
envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of
phospholipids.
integral protein - Answers 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 one or both sides of the membrane (or lining
the channel in the case of a channel protein).
peripheral protein - Answers a protein loosely bound to surface of a membrane or to part of an
integral protein and not embedded in the lipid bilayer
glycolipid - Answers a lipid with one or more covalently attached carbohydrates
glycoprotein - Answers a protein with one or more covalently attached carbohydrates
transport protein - Answers a transmembrane protein that helps a certain substance or class of
closely related substances to cross the membrane
aquaporin - Answers a channel protein in the plasma membrane of a plant, animal or
microorganism cell that specifically facilitates osmosis, the diffusion of free water across the
membrane
diffusion - Answers the spontaneous movement of a substance down its concentration or
electrochemical gradient, from a region where it is more concentrated to a region where it is
less concentrated.
concentration gradient - Answers a region along which the density of a chemical substance
increases or decreases.
passive transport - Answers the diffusion of a substance across a biological membrane with no
expenditure of energy
osmosis - Answers the diffusion of free water across a selectively permeable membrane
tonicity - Answers the ability of a solution surrounding a cell to cause that cell to gain or loose
water.
isotonic - Answers referring to a soultion that, when surrounding a cell, causes no net
, movement of water into or out of a cell
hypertonic - Answers referring to a solution that, when surrounding a cell, will cause the cell to
lose water
hypotonic - Answers referring to a solution that, when surrounding a cell, will cause the cell to
take up water.
osmoregulation - Answers regulation of solute concentrations and water balance by a cell or
organism
turgid - Answers swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a
lower water potential then its surroundings, resulting in entry of water.
flaccid - Answers lacking turgor (stiffness or firmness), as in the plant cell in surroundings
where there is a tendency for water to leave the cell. ( A wall cell becomes flaccid if it has a
higher water potential than its surroundings, resulting in the loss of water.)
plasmolysis - Answers 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 - Answers the passage of molecules or ions down their electrochemical
gradient across a biological membrane with the assistance of specific transmembrane
transport proteins, requiring no energy expenditure.
ion channels - Answers a transmembrane protein channel that allows a specific ion to diffuse
across the membrane down its concentration or electrochemical gradient.
gated channels - Answers a transmembrane protein channel that opens or closes in response to
a particular stimulus
active transport - Answers the movement of a substance across a cell membrane against its
concentration gradient, mediated by specific transport proteins and requiring an expenditure of
energy
sodium-potassium pump - Answers a transport protein in the plasma membrane of animal cells
that actively transports sodium out of the cell an potassium into the cell
membrane potential - Answers the difference in electrical charge (voltage) across a cell's
plasma membrane due to the differential distribution of ions. Membrane potential affects the
activity of excitable cells and the transmembrane movement of all charged substances.
electrochemical gradient - Answers the diffusion gradient of an ion, which is affected by both
the concentration difference of an ion across a membrane (a chemical force) and the ion's
tendency to move relative to the membrane potential (an electrical force).
