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37 Cards in this Set
- Front
- Back
Transport Across Membranes
What membranes do? (2) Why transport is important? (2) |
-What membranes do
=Separate material: ICF / ECF =Allow exchange of material: ICF / ECF -Why transport is important =Obtaining O2 and nutrients =Getting rid of waste products |
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Membranes Are Selective (4)
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-Selectively permeable
=Permeable = to pass through =Selective = restrictive -Membranes allow the transport of some substances, but not others |
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Extracellular Environment (5)
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-Includes all constituents of body outside cells
-7% of total body H20 is inside cells (intracellular fluid) -33% is outside cells (extracellular fluid-ECF) =20% of ECF is blood plasma =80% of ECF is interstitial fluid contained in gel-like matrix |
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Transport Across Plasma Membrane (2)
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-Plasma membrane is selectively permeable--allows only certain kinds of molecules to pass
-Many important molecules have transporters & channels |
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Carrier-mediated transport ...
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involves specific protein transporters
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Non-carrier mediated transport ...
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occurs by diffusion
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Passive transport ...
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moves compounds down concentration gradient; requires no energy
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Active transport ...
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moves compounds up a concentration gradient; requires energy & transporters
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Driving Forces (4)
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-Include chemical and electrical forces
-Both forces = electrochemical force =Passive +Movement down the force =Active +Movement against the force |
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Diffusion
Is random motion of molecules |
Net movement is from region of high to low concentration
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Non-polar compounds
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readily diffuse thru cell membrane
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Cell membrane is impermeable to
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charged & most polar compounds
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Charged molecules must have an ___ or ___ to move across membrane
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ion channel or transporter
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Rate of diffusion depends on: (4)
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-Magnitude of its concentration gradient
-Permeability of membrane -Temperature -Surface area of membrane |
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Chemical Driving Force
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Magnitude of chemical driving force proportional to concentration gradient
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A substance will diffuse down its own
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concentration gradient
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Electrical Driving Force
Direction of force depends on |
Polarity charge on particle
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Osmosis
Is net diffusion of H20 across a selectively permeable membrane (3) |
-H20 diffuses down its own concentration gradient
-H20 is less concentrated where there are more solutes -H20 diffuses down its concentration gradient until its concentration is equal on both sides of membrane |
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Isotonic
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have same osmotic pressure – concentration
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Hypertonic
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-have higher osmotic pressure – conc.
=Will have higher solute conc. than cell =Cell will lose water |
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Hypotonic (2)
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-have lower osmotic pressure
=Will have lower solute conc. than cell =Cell will gain water =Cell 65% solute (35% water) =Outside 55% solute (45% water) |
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Osmolality vs. Tonicity (2)
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-Tonicity implies a membrane that is impermeable to the solutes on either side of it.
-Osmolality is a measure of the osmotically active particles in a solution. It makes no explicit assertion with respect to the solute permeability of any involved membranes |
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Isosmotic
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solutions have same osmolality as plasma
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Hypo-osmotic
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solutions have lower osmotic pressure than plasma
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hyperosmotics
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have higher pressure than plasma
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Osmolality
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is 1mole in 1kg H2O
=Mole is number of molecules and thus gives us the ratio to water (thus concentration) |
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Regulation of Blood Osmolality (4)
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-Blood osmolality maintained in narrow range around 300m Osm
-If dehydrated, osmoreceptors in hypothalamus stimulate: =ADH release +Which causes kidney to conserve H20 =& thirst |
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Two aqueous solutions are separated by a semipermeable membrane. Solution A is 10% starch, and solution B is 5% starch. What will occur?
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Water will move from solution B to solution A.
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Two aqueous solutions are separated by a semipermeable membrane. Solution A is 10% water, and solution B is 5% water. What will occur?
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Water will move from solution A to solution B.
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A cell is placed into a hypertonic solution. What will occur?
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Water will move out of the cell.
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A cell has an osmolality of 300 and is placed into a solution with a osmolality of 600. What will be the net movement of water?
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Water will move out of the cell.
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Molecules too large & polar to diffuse are transported across membrane by ___
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protein carriers
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Active Transport
Example: Sodium–Potassium Pump |
-Uses ATP to move 3 Na+ out & 2 K+ in
=Against their gradients |
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Active Transport
Sodium linked glucose pump (3) |
-Secondary active transport of glucose
-Diffusion of Na+ provides energy -Pump actively transports glucose |
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Transport Across Epithelium (2)
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-Transport across cell
-Involves two membranes |
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Epithelium: Glucose Transport (3)
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-Secondary active transport: apical
-Facilitated diffusion: basolateral -Glucose transported across cell |
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Cystic Fibrosis (2)
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-Thick respiratory mucus
-Defect in transport mechanism |