membrane transport1
TRANSCRIPT
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The Cell as the The Cell as the Fundamental Unit of Fundamental Unit of
Life: Life: Membrane Membrane Transport ProcessesTransport Processes
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Selectively permeable- allows certain substances to pass through
By 2 ways: active or passive transport
Passive- downhill
Active- uphill (needs energy)
Plasma Membrane Function:Plasma Membrane Function:
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Passive: downhill reaction• Simple diffusion• Osmosis• Facilitated diffusion• Filtration
Active: uphill reaction, needs ATP• Exocytosis• Endocytosis
- Pinocytosis- Phagosytosis
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No Barrier: Substances “spread out”
High concentration to low concentration
e.g.: Red dye placed in glass of water
Passive Diffusion
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Substances diffuse
High concentration to low concentration
Pores in membrane must be large
“Down the concentration gradient”
Dynamic equilibrium, equal rates in both directions
Passive Diffusion
Biological membrane:
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Facilitated
Diffusion
Carrier proteins:
• Bind specific molecule & change shape
• Pass molecule through middle of protein
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Passive Diffusion: OsmosisOsmosis- diffusion of a water through a semi-permeable membrane
•Moves down concentration gradient
e.g. Two sugar solutions of different concentrations separated by porous membrane which lets water through but not sugar
What will happen?
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Passive Diffusion: Terms & Osmosis
More concentrated to less concentrated Until concentration same on both sides: isotonic
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Passive Diffusion: Osmosis &Terms
Concentration of solute less: solution is hypotonic.
Concentration of solute greater: solution is hypertonic.
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Passive Diffusion: Osmosis: Outcomes to Living Cells (Animal)
Animal cells No cell walls
Isotonic environment: Influx of water equals the efflux of water No change in cell shape
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Passive Diffusion: Osmosis: Outcomes to Living Cells (Animal)
Hypotonic solution: Water enters cell Bursts, or lyses
Hypertonic solution: Water leaves cell Shriveled, or crenate
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Passive Transport and Facilitated Diffusion
Passive transport & facilitated diffusion do NOT require
ATP
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Active Transport
DOES require the input of
ATP
Transport proteins AGAINST concentration
gradient
outside cell
inside cell
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ATPATP
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Role of ATP in Energy Role of ATP in Energy MetabolismMetabolism
ATP ATP ADP + P ADP + Pii + Energy + Energy
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EndocytosisEndocytosis
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ExocytosisExocytosis
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SecretionSecretion
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ExocytosisExocytosis
nuclei
mucus
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Membrane Permeability
Cell membrane:
selectively permeable
4 factors that determine permeability lipid solubility
molecular size
polarity
charge
1
2
3
4
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Lipid solubility Most important factor
Hydrophobic molecules Passively diffuse Hydrocarbons, carbon dioxide, & oxygen
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Molecular Size and Polarity
Larger molecules, less permeable Lower kinetic energy Small pore sizes in the membrane
Polar molecules hydrophilic, less permeable Very small, polar uncharged (water) molecules can diffuse
-+
Molecular Size
Polarity
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Charge
Charged molecules hydrophilic, less permeable Surrounded by coat of water (hydration shell), increases the size