Download Passive Transport (Chapter 7.4)

Passive Transport (Chapter 7.4)
Passive transport­ movement across the cell membrane that does not require energy from the cell.
Brownian Motion­ random motion of atoms and molecules.
­solids, liquids, and gases.
Diffusion­ the net movement of particles from an area of higher
concentration to an area of lower concentration (perfume or food coloring and water)
­ results because of Brownian motion.
3 Key Factors that affect Diffusion
1. Concentration: the more concentrated the more rapidly diffusion will occur (collisions with more particles).
2. Temperature: Increased temp. =increased energy = more rapid particle motion à increases rate of diffusion
3. Pressure: Increased pressure = increased particle motion =
increased rate of diffusion
Equilibrium ­when the concentration of a substance is equal throughout a space.
­materials moving out of the cell equals the materials moving into the cell.
Concentration Gradient­ a difference in the concentration of a substance across a space
­ food coloring example
Ions and molecules move with the gradient. Why?
Because they move from higher concentration to lower concentration (diffusion)
**If there are no interruptions, diffusion will continue until there is no longer a concentration gradient
­At this point dynamic equilibrium occurs
Note: Diffusion doesn’t have to only take place using substances in aqueous environment.
Example: Oxygen (gas) diffuses into capillaries because oxygen concentration is higher in lung air sacs then the concentration in the capillaries
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Osmosis­ diffusion of water across a selectively permeable membrane
What controls Osmosis?
­concentration gradient
Osmosis affects cells
­most cells surrounded by water
3 types of solutions
1.
hypertonic solution
a. water moves out of the cell
b. causes the cell to shrink
c. animal cell shrivels and wilting plants
outside the cell
Dissolved particles
Water molecules
2.
hypotonic solution
a. water moves into the cell
b. causes cell to swell
c. could cause animal cells to burst and plant cells to become plump. (plant cells won't burst because the cell wall protects it)
outside the cell
Dissolved particles
Water molecules
3.
inside the cell
Dissolved particles
Water molecules
inside the cell
Dissolved particles
Water molecules
Isotonic Solution
a. No net water movement.
b. Water diffuses into and out of the cell at equal rates
c. Cell stays the same size
d. Dissolved particles and water molecules are = in and out of the cell
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Crossing the Cell Membrane
Reminder: transport proteins (channel)
Ions like Na, K, Ca, and Cl can not pass through the nonpolar inner part of the membrane because they are polar but they can diffuse through ion channels.
ion channels ­ a transport protein with a polar pore through which ions can pass. Facilitated Diffusion
Carrier proteins transport substances down their concentration gradient through a process called
Facilitated diffusion­ type of passive transport that does not require any energy.
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