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28 Cards in this Set
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- Back
- 3rd side (hint)
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active transport
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The movement of a substance across a biological membrane against its concentration or electrochemical gradient with the help of energy input and specific transport proteins.
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36.738
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apoplast
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In plants, the nonliving continuum formed by the extracellular pathway provided by the continuous matrix of cell walls.
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36.743
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aquaporin
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A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane (osmosis).
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36.742
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bulk flow
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The movement of water due to a difference in pressure between two locations.
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36.743
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Casparian strip
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A water-impermeable ring of wax around endodermal cells in plants that blocks the passive flow of water and solutes into the stele by way of cell walls.
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36.745
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chemiosmosis
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An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Most ATP synthesis in cells occurs by _____.
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36.740
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circadian rhythm
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A physiological cycle of about 24 hours that is present in all eukaryotic organisms and that persists even in the absence of external cues.
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36.751
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cotransport
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The coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient.
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36.740
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endodermis
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The innermost layer of the cortex in plant roots; a cylinder one cell thick that forms the boundary between the cortex and the stele.
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36.744
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flaccid
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Limp. Walled cells are ____in isotonic surroundings, where there is no tendency for water to enter.
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36.741
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guttation
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The exudation of water droplets, caused by root pressure in certain plants.
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36.746
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megapascal (MPa)
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A unit of pressure equivalent to 10 atmospheres of pressure.
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36.740
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membrane potential
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The charge difference between the cytoplasm and extracellular fluid in all cells, due to the differential distribution of ions. ____ affects the activity of excitable cells and the transmembrane movement of all charged substances.
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36.738
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mycorrhiza
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A mutualistic association of plant root and fungus.
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36.744
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osmosis
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The diffusion of water across a selectively permeable membrane.
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36.740
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passive transport
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The diffusion of a substance across a biological membrane.
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36.738
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plasmolysis
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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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36.742
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proton pump
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An active transport mechanism in cell membranes that consumes ATP to force hydrogen ions out of a cell and, in the process, generates a membrane potential.
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36.738
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root pressure
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The upward push of water within the stele of vascular plants, caused by active pumping of minerals into the xylem by root cells.
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36.746
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sugar sink
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A plant organ that is a net consumer or storer of sugar. Growing roots, shoot tips, stems, and fruit are ____ supplied by phloem.
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36.752
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sugar source
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A plant organ in which sugar is being produced by either photosynthesis or the breakdown of starch. Mature leaves are the primary ____ of plants.
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36.752
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symplast
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In plants, the continuum of cytoplasm connected by plasmodesmata between cells.
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36.743
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tonoplast
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A membrane that encloses the central vacuole in a plant cell, separating the cytosol from the cell sap.
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36.743
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transfer cells
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Companion cells with numerous ingrowths of their walls which increase the cells' surface area and enhance the movement of solutes between apoplast and symplast.
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36.752
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transpiration
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The evaporative loss of water from a plant.
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36.746
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transport protein
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A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.
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36.738
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turgid
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Firm. Walled cells become turgid as a result of the entry of water from a hypotonic environment.
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36.742
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water potential
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The physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure.
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36.740
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