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34 Cards in this Set
- Front
- Back
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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Apoplast
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In plants, the continuum of cell walls plus the extracellular spaces.
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Aquaporins
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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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Bulk flow
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The movement of water due to a difference in pressure between two locations.
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Casparian strip
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A water0impermeable ring of wax in the endodermal cells of plants that blocks the passive flow of water and solutes into the stele by way of cells walls.
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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 chemiosmosis.
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Circadian rhythms
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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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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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Endodermis
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The innermost layer of the cortex in plant roots; a cylinder one cell think that forms the boundary between the cortex and the vascular cylinder.
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Flaccid
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Limp. A walled cell is flaccid in surroundings where there is no tendency for water to enter.
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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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Megapascals (MPa)
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A unit of pressure equivalent to 10 atmospheres of pressure.
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Membrane potential
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The charge difference between a cell’s cytoplasm and the extracellular fluid, due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances.
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Mycorrhizae
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Mutualistic associations of plant roots and fungi.
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Osmosis
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The diffusion of water across a selectively permeable membrane.
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Osmotic potential
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A component of water potential that is proportional to the number of dissolved solute molecules in a solution and measures the effect of solutes on the direction of water movement; also called solute potential, it can be either zero or negative.
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Plasmolyze
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To shrink and pull away from a cell wall, or when a plant cell protoplast pulls away from the cell wall as a result of water loss.
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Pressure potential (Ψp)
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A component of water potential that consists of the physical pressure on a solution, which can be positive, zero, or negative.
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Proton pump
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An active transport mechanism in cell membranes that uses ATO to force hydrogen ions out of a cell, generating a membrane potential in the process.
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Root pressure
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The upward push of xylem sap in the vascular tissue of roots.
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Solute potential (Ψs)
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A component of water potential that is proportional to the number of dissolved solute molecules in a solution and measures the effect of solutes on the direction of water movement; also called osmotic potential, it can be either zero or negative.
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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 fruits are sugar sinks supplied by phloem.
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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 sugar sources of plants.
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Symplast
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In plants, the continuum of cytoplasm connected by plasmodesmata between cells.
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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 vacuolar contents, called cell sap; also known as the vacuolar membrane.
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Transfer cells
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A companion cell with numerous ingrowths of its wall, increasing the cell’s surface area and enhancing the transfer of solutes between apoplast and symplast.
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Transpiration
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The evaporative loss of water from a plant.
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Transport proteins
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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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Turgid
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Very firm. A walled cell becomes turgid if it has a greater solute concentration than its surroundings, resulting in entry of water.
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Turgor pressure
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The force directed against a cell wall after the influx of water and the swelling of a walled cell due to osmosis.
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Vacuolar membrane
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A membrane that encloses the central vacuole in a plant cell, separating the cytosol from the vacuolar contents, called cell sap; also known as the tonoplast.
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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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Wilting
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The drooping of leaves and stems as a result of plant cells becoming flaccid.
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Xerophytes
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A plant adapted to an arid climate.
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