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1.14 Passive Transport

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

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1.14 Passive Transport

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  1. 1.14Passive Transport

  2. Electrolyte – positive/negative ions dissolved in an aqueous solution

  3. Simple Diffusion • Selectively permeable – allows only certain substances to pass through it • Many small, uncharged molecules (ex. H2O, O2, CO2) pass through the CM 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

  4. 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 CM

  5. 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

  6. Facilitated Diffusion • Facilitated diffusion – the diffusion of solutes through a membrane assisted by proteins • Amino acids, carbohydrates, nucleic acids, and large lipids can’t move through the CM • These substances need help getting through the CM – do so through membrane proteins

  7. There are 3 types of membrane proteins: 1. Attached to the outside of the CM 2. Go partway through the P-lipid bilayer 3. Go all the way through the P-lipid bilayer

  8. Transmembrane Proteins • Carrier Protein – a transmembrane protein that facilitates the diffusion • Only transports one type of substance or related substances • Ex. Movement of glucose cells into the liver

  9. Osmosis • Osmosis – 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]; Low [H2O] = High [solute] • Water moves through a membrane from a side with low [solute] to the side with high [solute]

  10. Isotonic solution – solution where [solute] is equal • Hypertonic solution – has higher [solute] • Hypotonic solution – has low [solute]

  11. Osmosis and Blood • Red blood cell cytoplasm and blood serum are isotonic • Osmosis doesn’t happen in RBCs

  12. 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

  13. 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

  14. Homework • Pg. 64 #1-8

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