Campbell: Biology in Focus Chapter 5
active transport - ANSWER The movement of a substance across a cell membrane against
its concentration or electrochemical gradient, mediated by specific transport proteins and requiring
an expenditure of energy.
amphipathic - ANSWER Having both a hydrophilic region and a hydrophobic region.
antiport - ANSWER A membrane transport process that carries one substance in one
direction and another in the opposite direction.
aquaporin - ANSWER 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.
autocrine signaling - ANSWER the target cell is also the secreting cell
carrier protein - ANSWER A type of transport protein that holds onto its passengers and
changes shape in a way that shuttles them across a membrane.
channel protein - ANSWER A type of transport protein that functions by having a
hydrophilic channel that certain molecules or atomic ions use as a tunnel through a membrane.
concentration gradient - ANSWER A region along which the density of a chemical substance
increases or decreases.
cotransport - ANSWER The coupling of the "downhill" diffusion of one substance to the
"uphill" transport of another against its own concentration gradient.
Crenation - ANSWER in animal cells, shriveling of the cell due to water leaving the cell when
the environment is hypertonic
cyclic AMP (cAMP) - ANSWER A compound formed from ATP that acts as a second
messenger.
diffusion - ANSWER The random thermal motion of particles of liquids, gases, or solids. In
the presence of a concentration or electrochemical gradient, diffusion results in the net movement
of a substance from a region where it is more concentrated to a region where it is less concentrated.
electrochemical gradient - ANSWER 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).
electrogenic pump - ANSWER An active transport protein that generates voltage across a
membrane while pumping ions.
endocrine signaling - ANSWER Specialized cells release hormone molecules into vessels of
the circulatory system, by which they travel to target cells in other parts of the body.
endocytosis - ANSWER Cellular uptake of biological molecules and particulate matter via
formation of vesicles from the plasma membrane.
exocytosis - ANSWER The cellular secretion of biological molecules by the fusion of vesicles
containing them with the plasma membrane.
active transport - ANSWER The movement of a substance across a cell membrane against
its concentration or electrochemical gradient, mediated by specific transport proteins and requiring
an expenditure of energy.
amphipathic - ANSWER Having both a hydrophilic region and a hydrophobic region.
antiport - ANSWER A membrane transport process that carries one substance in one
direction and another in the opposite direction.
aquaporin - ANSWER 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.
autocrine signaling - ANSWER the target cell is also the secreting cell
carrier protein - ANSWER A type of transport protein that holds onto its passengers and
changes shape in a way that shuttles them across a membrane.
channel protein - ANSWER A type of transport protein that functions by having a
hydrophilic channel that certain molecules or atomic ions use as a tunnel through a membrane.
concentration gradient - ANSWER A region along which the density of a chemical substance
increases or decreases.
cotransport - ANSWER The coupling of the "downhill" diffusion of one substance to the
"uphill" transport of another against its own concentration gradient.
Crenation - ANSWER in animal cells, shriveling of the cell due to water leaving the cell when
the environment is hypertonic
cyclic AMP (cAMP) - ANSWER A compound formed from ATP that acts as a second
messenger.
diffusion - ANSWER The random thermal motion of particles of liquids, gases, or solids. In
the presence of a concentration or electrochemical gradient, diffusion results in the net movement
of a substance from a region where it is more concentrated to a region where it is less concentrated.
electrochemical gradient - ANSWER 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).
electrogenic pump - ANSWER An active transport protein that generates voltage across a
membrane while pumping ions.
endocrine signaling - ANSWER Specialized cells release hormone molecules into vessels of
the circulatory system, by which they travel to target cells in other parts of the body.
endocytosis - ANSWER Cellular uptake of biological molecules and particulate matter via
formation of vesicles from the plasma membrane.
exocytosis - ANSWER The cellular secretion of biological molecules by the fusion of vesicles
containing them with the plasma membrane.
