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18 Cards in this Set
- Front
- Back
Roles of membrane Proteins? |
- clip into one another forming tight junctions -create channels for communication between adjacent cells (gap junctions) -attach to cytoskeleton / extracellular matrix helping to maintain cell shape/position of the cell in the tissue. |
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types of membrane proteins |
- peripheral: attached to the inner or the outer face of the membrane -Integral: embedded right in/through the membrane |
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what do phospholipids vary according to? |
head groups, fatty acid tail length, degree of unsaturation |
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Cholestrol improves membrane stability |
help hold a more solid membrane but also help to keep membrane from completely solidifying Decrease membrane permeability to small water soluble molecules |
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lipid rafts (in membrane): |
more solid areas of the membrane taht span a greater diameter. greater amounts of cholestrol here. contribute to membrane polarity. |
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what is the interaction of peripheral proteins with the membrane? |
they are attached to one single face of membrane or to another protein through ELECTROSTATIC INTERACTIONS |
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types of integral proteins: |
transmembrane proteins: contain hydrophobic stretches that allow the protein to span the entire membrane 1-12 times. non-covalently attached to the membrane lipid anchored protein: attached directly to the membrane lipid, often covalently, other times attached to the lipid by a carbohydrate bridge. protein is to one side of the membrane only. common in lipid rafts |
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what is cytoskeleton |
an intracellular network of insoluble protein, composed of microfilaments, intermediate filaments, microtubules. important for cell shape and motility of intracellular material. |
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where does the extracellular matrix come from? |
its produced and secreted by cells in a given tissue. composition and density depends on the tissue type. it is composed of glycoprotein (proteoglycans) and protein fibers. |
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Muscular Dystrophy: |
pathological condition unable to produce proper form of dystrophin anchors the cytoskeleton to the extracellular matrix important for shock absorption results in muscles that are easily damaged |
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Malignant Cancer |
pathological condition cancer cells able to break free from the extra-cellular matrix can migrate to other locations in the body |
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what impacts diffusion? |
polarity of a solute together with solute size impact whether or not diffusion is possible. polar molecules including sugars and ions require hydrophilic protein channels to cross the hydrophobic membrane interior. |
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what alters the rate of diffusion? |
-Temperature -Solute size: smaller molecules have faster rate of diffusion -Distance travelled: doubling the distance travelled, increases the transit time by distance^2 -molecules able to diffuse freely will do so more quickly than molecules needing to cross a membrane. |
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any polar molecules cross the membrane through diffusion? |
water is able to pass from areas of low concentration of areas of high concentration because of aquaporins. Urea which is small and polar can also move freely. |
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effect of membrane composition on diffusion? |
High cholesterol and protein concentration in the membrane will slow diffusion. types of phospholipids present will also determine the rate of diffusion |
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membrane permeability if proportional to: |
lipid solubility / molecular size |
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fick's law of diffusion |
diffusion rate will directly increase when the concentration gradient, surface area, or membrane permeability increase. |
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tonicity |
describes volume changes for a cell in a solution. tonicity always compares the solution to the cell and describes only the solution. |