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62 Cards in this Set
- Front
- Back
plasma membrane |
theboundary that separates the living cell from its surroundings |
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selective permeability |
plasma membrane trait allowingsome substances to cross it more easily than others |
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amphipathic |
has a hydrophilic head region and ahydrophobic tail region |
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mostof the membrane’s specific functions |
proteins determine: |
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peripheral proteins |
bound to the surface of the membrane |
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integral proteins |
penetratethe hydrophobic core |
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transmembrane proteins |
Integralproteins that span the membrane |
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alpha helices |
hydrophobicregions of an integral protein consist of one or more stretches ofnonpolaramino acids, often coiled into |
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1.Transport 2.Enzymaticactivity 3.Signaltransduction 4.Cell-cellrecognition 5.Intercellularjoining 6.Attachmentto the cytoskeleton and extracellular matrix (ECM) |
functions of membrane proteins (6) |
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transport |
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enzymatic activity |
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signal transduction
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cell- cell recognition |
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intercellular joiing |
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ECM |
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hydrophobic (non-polar) |
___________ molecules,such as hydrocarbons, can dissolve in the lipid bilayer and pass through themembrane rapidly ex. gases (O2, CO2),lipids, steroids |
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hydrophilic |
___________ moleculesincluding ions and polar molecules do not cross the membrane easily |
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transport proteins |
allowpassage of hydrophilic substances across the membrane |
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channel proteins |
havea hydrophilic channel that certain molecules or ions can use as a tunnel |
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aquaporins |
channelproteins that facilitate the passage of water |
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carrier proteins |
bindto molecules and change shape to shuttle them across the membrane |
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diffusion |
thetendency for molecules to spread out evenly into the available space |
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dynamic equilibrium |
asmany molecules cross the membrane in one direction as in the other (no netmovement) |
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concentration gradient |
theregion along which the density of a chemical substance increases or decreases |
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down |
Substancesdiffuse ______ their concentrationgradient, which requires no energy |
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passive transport |
Thediffusion of a substance across a biological membrane if noenergy is expended by the cell to make it happen -spontaneous, -deltaG -molecules/ions become less organized |
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simple diffusion |
themovement of gases (O2,CO2) and lipids through thephospholipid bilayer. |
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facilitated diffusion |
Larger and more polar molecules andions cannot pass through the bilayer – requires help from membrane proteinsthrough the process of |
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-Channelproteins -Aquaporins -Ion channels -carrier proteins |
types of transport proteins used in facilitated diffusion |
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active trasport |
movessubstances against their concentration gradients -requires energy -performed by carrier proteins embedded in membrane only ex. Na-K pump |
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passive transport |
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active transport |
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membrane potential |
thevoltage difference across a membrane |
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voltage |
createdby differences in the distribution of positive and negative ions across amembrane |
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negative |
Thenormal resting membrane potential of a human cell is _________. |
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electrochemical gradient |
Twocombined forces drive the diffusion of ionsacross a membrane |
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electrical force |
the effect of the membranepotential on the ion’s movement |
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chemical force |
the ion’sconcentration gradient |
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electrogenic pump |
atransport protein that generates voltage across a membrane -ex. Na-K pump |
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proton pump |
Themain electrogenic pump of plants, fungi, andbacteria |
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co-transport |
whenactive transport of a solute indirectly drives transport of othersubstances |
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bulk transport |
transport of largemolecules, such as polysaccharides and proteins to cross the membrane -requires ATP |
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exocytosis |
transportvesicles migrate to the membrane, fuse with it, and release their contentsoutside the cell -used by hormone secretory cells -moves a large number of molecules |
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endocytosis |
thecell takes in macromolecules by forming vesicles from the plasma membrane |
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-Phagocytosis (“cellulareating”) -Pinocytosis (“cellulardrinking”) -Receptor-mediated endocytosis |
Types of endocytosis (3) |
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phagocytosis |
cellengulfs a particle in a vacuole. vacuole fuses with a lysosome and is broken down by digestive enzymes |
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pinocytosis |
molecules dissolved in droplets are taken up when extracellular fluid is “gulped” into tiny vesicles -Usually performed to take in H2O -Non-specific |
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receptor-mediated endocytosis |
binding of ligands to receptors triggers vesicle formation -brings in large number of specific molecules ex.human cells use this to take in cholesterol |
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ligand |
any molecule that binds specifically to areceptor site of another molecule |
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hypercholesterolemia |
inherited disease where LDL receptors aredefective, cholesterol not taken into cells, stays in blood |
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osmosis |
thediffusion of water across a selectively permeable membrane |
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lower; higher |
Waterdiffuses across a membrane from the region of _______ solute concentration to the region of _______ solute concentration until thesolute concentration is equal on both sides |
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tonicity |
theability of a surrounding solution to cause a cell to gain or lose water -Dependenton non-penetrating [solute] and membrane permeability |
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isotonic solution |
Soluteconcentration is the same as that inside the cell; no net water movement across the plasmamembrane |
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hypertonic solution |
Soluteconcentration is greater than that inside the cell; cell loses water |
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hypotonic solution |
Soluteconcentration is less than that inside the cell; cell gains water |
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osmoregulation |
thecontrol of solute concentrations and water balance; a necessary adaptationfor life in such environments |
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water balance |
Cellwalls help maintain |
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turgid
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Aplant cell in a hypotonic solution swells until the wall opposes uptake; thecell is now ______. |
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flaccid |
If aplant cell and its surroundings are isotonic, there is no net movement of waterinto the cell;the cell becomes _________. |
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lose water |
In ahypertonic environment, plant cells: |
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plasmolysis |
In a hypertonic environment themembrane pulls away from the cell wall causing the plant to wilt, a usuallylethal effect called ________. |