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33 Cards in this Set
- Front
- Back
Peripheral Proteins |
bound to surface of membrane |
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Integral Proteins |
penetrate the hydrophobic core |
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selective permeability
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some substances to cross more easily than others
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Fluid mosaic model
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membrane is a fluid structure with a “mosaic” of various proteins embedded in it
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Six major functions of membrane proteins
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1.Transport
2.Enzymatic activity 3.Signal transduction 4.Cell-cell recognition 5.Intercellular joining 6.Attachment to the cytoskeleton and extracellularmatrix (ECM) |
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glycolipids
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Membrane carbohydrates may be covalentlybonded to lipids
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glycoproteins
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Membrane carbohydrates may be bonded to proteins
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Transport proteins
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allow passage of hydrophilicsubstances across the membrane
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aquaporins |
facilitate thepassage of water
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Diffusion |
tendency for molecules to spread out evenly into the available space.
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concentration gradient
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the region along which the density of achemical substance increases or decreases
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passive transport
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no energy is expended by the cell to make it happen
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Osmosis
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diffusion of water across a selectively permeable membrane
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Tonicity
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ability of a surrounding solution to causea cell to gain or lose water
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Isotonic Solution
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solute concentration is the sameas that inside the cell; no net water movement across the plasma membrane
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Hypertonic Solution
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solute concentration is greater than that inside the cell; cell loses water
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Hypotonic Solution
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solute concentration is less than that inside the cell; cell gains water
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Osmoregulation
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the control of solute concentrations and water balance, it is a necessary adaptation for life in such environments
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Turgid
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firm |
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Flaccid |
limp |
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Plasmolysis
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plant cells lose water;eventually, the membrane pulls away from the cell wall causing the plant to wilt.
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Facilitated diffusion |
transport proteins speed thepassive movement of molecules across membrane; include channel proteins and carrier proteins |
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Ion channels
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facilitate the diffusion of ions
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Gated channels
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open or close in response to a stimulus
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Active transport
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moves substances against their concentration gradients
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Membrane potential
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voltage difference across a membrane
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electrochemical gradient
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drive the diffusion of ions across a membrane
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Electrogenic pump
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transport protein that generates voltage across a membrane
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proton pump
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The main electrogenic pump of plants, fungi, and bacteria
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Cotransport
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active transport of a solute indirectly drives transport of other substances
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Exocytosis
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transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell
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Endocytosis
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cell takes in macromolecules by forming vesicles from the plasma membrane
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three types of endocytosis
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1.Phagocytosis (“cellular eating”) cell engulfs particle in a vacuole.
2.Pinocytosis (“cellular drinking”) molecules taken up when extracellular fluid is “gulped” into tiny vesicles. 3.Receptor-mediated endocytosis: binding of ligands to receptors triggers vesicle formation. |