Post on 17-Dec-2015
Osmosis and Diffusion!
IMPORTANT DEFINITIONS
DIFFUSION: movement of particles from higher concentration to lower concentration
DIFFUSION
OSMOSIS: diffusion of water across a selectively permeable membrane
In a cell, water always tries to reach an equal concentration on both sides of the membrane!
OSMOSIS
Vocabulary Terms to KnowConcentration = density of particles
Permeable = allows things to pass throughSelectively Permeable = allows certain
things only to pass through Impermeable = allows nothing to pass
throughSolute = you addSolvent = added to
During osmosis, only water diffuses across the
selectively permeable membrane.
OSMOSIS
Gotta love the Greeks!
ISOS=equalHYPO=underHYPER=over
Remember your roots!
Hypotonic Solution
A cell is placed in pure water
There is a lower concentration of solutes (dissolved substances )outside the cell than inside the cell.
Water will flow into the cell.
Isotonic Solution Equal concentrations of
solutes inside and outside the cell.
Water will flow into and out of the cell at equal rates (dynamic equilibrium)
EX: Immunizations are isotonic solutions so they do not damage the cells by gain or loss of water.
Hypertonic Solution
A cell is placed in a concentrated salt solution (seawater)
There is a higher concentration of solutes outside the cell than inside the cell.
Water will flow out of the cell
Note: These are animal red blood cells. The size of the arrows indicates the magnitude and
direction with which water moves.
What about the big boys?
ENDOCYTOSIS: cells surrounds and takes in material from environment by engulfing the material! YUMMY!
EXOCYTOSIS: cells expel materials from cell, such as waste or indigestible particles. GROSS!
Both endo and exocytosis are moving large masses of material and require energy (ACTIVE TRANSPORT!)
Endocytosis
Exocytosis
ISOTONIC SOLUTIONS!
Concentration of dissolved substances in solution is the same as concentration of dissolved substances inside the cell.
Water inside cell is equal to water in solution.
Cells in isotonic solution do not experience osmosis and retain their normal shape.
EX: Immunizations are isotonic solutions so they do not damage the cells by gain or loss of water.
HYPOTONIC SOLUTIONS! Concentration of dissolved substances
is lower in solution outside the cell than concentration inside the cell.
There is more water outside the cell than inside.
Cells in hypotonic solutions experience osmosis in which water moves through membrane into cell.
EX: In animal cells, the pressure inside cell increases causing the cells to swell and sometimes burst!
EX: In plant cells, the rigid cell wall prevents bursting, but the cells become more firm.
CUCUMBERS IN THE MIST!
HYPERTONIC SOLUTIONS! Concentration of dissolved substances
outside cell is higher than concentration inside cell.
There is more water inside cell than outside.
Cells in hypertonic solutions experience osmosis in which water moves through membrane to outside of cell.
Ex: In plant cells, membrane and cytoplasm shrink away from cell wall and plant wilts.
EX: In animal cells, the pressure decreases and the cells shrivel.
Don’t be so SALTY!
Passive Transport: Mosey on through…
Passive transport is what it sounds like!
Molecules pass through the membrane by diffusion requiring no extra energy.
The molecules just mosey on through the membrane.
Ex: Some of the molecules that move by passive transport are: water and lipids
Passive Transport
Facilitated Diffusion: Help them out a bit!
Remember those transport proteins in the phospholipid bilayer? Here’s
where they fit in!Facilitated diffusion: passive
transport across membrane with help of transport proteins.
Ex: Facilitated diffusion is used to move sugars and amino acids across membranes.
Facilitated Transport
Active Transport: ENERGY REQUIRED!
Active transport is the movement of materials through a membrane across a concentration gradient.
This requires energy to counteract the movement of diffusion from high to low concentrations!
How does it work?1) Transport protein called “carrier
protein” binds with particle that is going to be transported.
2) Because of its specific shape, the carrier protein can bind to the particle and with some energy, it can move through the membrane.
3) Once the particle is released, the protein returns to its original shape.
Active transport allows a particle movement into or out of a cell against
a concentration gradient.
How carrier proteins work!
Active Transport
Active Transport
Cellular Transport