1.14 passive transport
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1.14 Passive Transport. Electrolyte – positive/negative ions dissolved in an aqueous solution. Simple Diffusion. Selectively permeable – allows only certain substances to pass through it - PowerPoint PPT PresentationTRANSCRIPT
1.14 Passive Transport
Electrolyte – positive/negative ions dissolved in an aqueous solution
Simple Diffusion
Selectively permeable – allows only certain substances to pass through it• Many small, uncharged molecules (ex. H2O, O2, CO2, fatty
acids) pass through the cell membrane freely either through the P-lipid bilayer or through protein channels throughout the membrane
Simple diffusion – the movement of particles from an area of high concentration to an area of low concentration until particle concentration is equal• Doesn’t use any of the cell’s energy
Concentration gradient – a difference in concentration between 2 areas
Dynamic equilibrium – a state of balance where particles move in all directions at equal rates• [particles] remains the same on both sides of
the cell membrane
The rate of diffusion depends on the temperature and the [solute molecules] in the solution
• Molecules move faster at higher temperatures
• There are more molecules to balance things out at higher concentrations
Facilitated DiffusionFacilitated diffusion – the diffusion of solutes through a membrane assisted by proteins
Amino acids, carbohydrates, nucleic acids, and large lipids can’t move through the cell membrane• These substances need help getting through the
membrane – do so through membrane proteins
Different proteins act in different ways to help substances across the membrane
• A channel protein can provide a channel through which the particle can travel. Ions such as sodium and chloride cross the membrane in this way.
• A carrier protein can bind to the particle, transport it across the membrane, and release it. Large polar molecules such as glucose cross the membrane in this way.
OsmosisOsmosis – the net movement of water across a selectively permeable membrane from an area of high concentration to an area of low concentration
• High [H2O] = low [solute] (dilute)• Low [H2O] = High [solute] (concentrated)
Isotonic solution – solution where [solute] is equal
Hypertonic solution – has higher [solute]
Hypotonic solution – has low [solute]
Osmosis and Blood
Red blood cell cytoplasm and blood serum are isotonic
Osmosis doesn’t happen in red blood cells
When a patient receives an IV drip, the IV solution mixes with blood serum• If the IV solution given is hypotonic (low [solute]) it might
dilute the blood serum• Blood serum is hypotonic to RBC cytoplasm• Osmosis will occur into the RBC, causing it to fill with fluid
and burst (hemolysis)– May be fatal because the RBCs won’t be able to transport O2
If the IV solution is hypertonic (high [solute]), it will concentrate the blood serum• Blood serum is hypertonic to the RBC cytoplasm• Osmosis will occur out of the RBC, causing it to shrivel
(crenation)– Can be fatal because the shrivelled cells can stick to one
another and clog veins and arteries
Homework
• Pg. 64 #1-11