AP Biology Vocabulary & Roots: Ch. 7
1. active transport-The movement of a substance across a cell membrane, with an expenditure of
energy, against its concentration or electrochemical gradient; mediated by specific transport
proteins.
2. ATP (adenosine triphosphate)- An adenine-containing nucleoside triphosphate that releases free
energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions
in cells.
3. amphipathic-Having both a hydrophilic region and a hydrophobic region.
4. aquaporin-A channel protein in the plasma membrane of a plant, animal, or microorganism cell
that specifically facilitates osmosis, the diffusion of water across the membrane.
5. carbohydrate-A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers
(polysaccharides).
6. concentration gradient-A region along which the density of a chemical substance increases or
decreases.
7. diffusion-The spontaneous movement of a substance down its concentration gradient, from a
region where it is more concentrated to a region where it is less concentrated.
8. electrochemical gradient-The diffusion gradient of an ion, which is affected by both the
concentration difference of the ion across a membrane (a chemical force) and the ion's tendency to
move relative to the membrane potential (an electrical force).
9. electrogenic pump-An ion transport protein that generates voltage across a membrane.
10. endocytosis-Cellular uptake of biological molecules and particulate matter via formation of new
vesicles from the plasma membrane.
11. exocytosis-The cellular secretion of biological molecules by the fusion of vesicles containing
them with the plasma membrane.
12. facilitated diffusion-The spontaneous passage of molecules or ions across a biological
membrane with the assistance of specific transmembrane transport proteins.
13. flaccid- Limp. Lacking in stiffness or firmness, as in a plant cell in surroundings where there is
no tendency for water to enter the cell.
14. gated channel-A transmembrane protein channel that opens or closes in response to a particular
stimulus.
15. glycogen-An extensively branched glucose storage polysaccharide found in the liver and muscle
of animals; the animal equivalent of starch.
16. glycolipid-A lipid with covalently attached carbohydrate(s).
17. glycoprotein-A protein with one or more carbohydrates covalently attached to it.
18. hypertonic-Referring to a solution that, when surrounding a cell, will cause the cell to lose
water.
19. hypotonic-Referring to a solution that, when surrounding a cell, will cause the cell to take up
water.
20. 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 (or lining the channel in the
case of a channel protein).
21. ion channel-A transmembrane protein channel that allows a specific ion to flow across the
membrane down its concentration gradient.
22. isotonic-Referring to a solution that, when surrounding a cell, has no effect on the passage of
water into or out of the cell.
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23. ligand-A molecule that binds specifically to another molecule, usually a larger one.
24. low-density lipoprotein (LDL)-A particle in the blood made up of cholesterol and other lipids
surrounded by a single layer of phospholipids in which proteins are embedded. LDL carries more
cholesterol than a related lipoprotein, HDL, and high LDL levels in the blood correlate wi
25. membrane potential-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.
26. model-A representation of a theory or process.
27. myosin-A type of protein filament that acts as a motor protein with actin filaments to cause cell
contraction.
28. osmoregulation-Regulation of solute concentrations and water balance by a cell or organism.
29. osmosis-The diffusion of water across a selectively permeable membrane.
30. passive transport-The diffusion of a substance across a biological membrane with no
expenditure of energy.
31. 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.
32. phagocytosis-A type of endocytosis in which large particulate substances are taken up by a cell.
It is carried out by some protists and by certain immune cells of animals (in mammals, mainly
macrophages, neutrophils, and dendritic cells
33. pinocytosis-A type of endocytosis in which the cell ingests extracellular fluid and its dissolved
solutes.
34. plasma membrane-The membrane at the boundary of every cell that acts as a selective barrier,
regulating the cell’s chemical composition.
35. 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.
36. 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.
37. receptor-mediated endocytosis-The movement of specific molecules into a cell by the inward
budding of membranous vesicles containing proteins with receptor sites specific to the molecules
being taken in; enables a cell to acquire bulk quantities of specific substances.
38. selective permeability-A property of biological membranes that allows them to regulate the
passage of substances.
39. 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.
40. tonicity- The ability of a solution surrounding a cell to cause that cell to gain or lose water.
41. transport protein-A transmembrane protein that helps a certain substance or class of closely
related substances to cross the membrane.
42. turgid-Swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a greater
solute concentration than its surroundings, resulting in entry of water.)
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Word Roots
amphi- = dual (amphipathic molecule: a molecule that has both a hydrophobic and a hydrophilic
region)
aqua- = water; -pori = a small opening (aquaporin: a transport protein in the plasma membrane of a
plant or animal cell that specifically facilitates the diffusion of water across the membrane)
co- = together; trans- = across (cotransport: the coupling of the "downhill" diffusion of one
substance to the "uphill" transport of another against its own concentration gradient)
electro- = electricity; -genic = producing (electrogenic pump: an ion transport protein generating
voltage across a membrane)
endo- = inner; cyto- = cell (endocytosis: the movement of materials into a cell; cell eating)
exo- = outer (exocytosis: the movement of materials out of a cell)
hyper- = exceeding; -tonus = tension (hypertonic: a solution with a higher concentration of solutes)
hypo- = lower (hypotonic: a solution with a lower concentration of solutes)
iso- = same (isotonic: solutions with equal concentrations of solutes)
phago- = eat (phagocytosis: cell eating)
pino- = drink (pinocytosis: cell drinking)
plasm- = molded; -lyso = loosen (plasmolysis: a phenomenon in walled cells in which the
cytoplasm shrivels and the plasma membrane pulls away from the cell wall when the cell loses
water to a hypertonic environment)
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