Cells: Diffusion And Osmosis

Cells Diffusion and Osmosis

Cells

have to control what leaves and what enters the cytoplasm.

Concentration Gradient Water

and solutes move according to their concentration gradient  Everything naturally moves

away from where it is concentrated and towards where it is less concentrated  This natural movement is called

Concentration gradients Concentration

gradients form when there is a difference in concentration between two places Diffusion takes place until the concentration reaches equilibrium

Diffusion naturally tries to equalize concentration of

Carbon dioxide naturally diffuses out of animal cells because animal cells

Movement of CO2 and O2  Oxygen

naturally diffuses into animal cells because they use up oxygen as they turn food into energy  Carbon dioxide builds up as cells use the oxygen  The concentration of oxygen outside is higher, so the net movement of O2 is inward.  The concentration of CO2 is higher inside the cell and has a net

The

cell membrane does not stop the diffusion of CO2, O2, or water molecules

CO2,

O2, and H2O are small molecules they each move down their individual concentration gradients until equilibrium is reached.

Salts and sugars cannot get through the bilayer, but water can This

makes the cell membrane semipermeable. The movement of water through a semipermeable membrane that blocks solutes from moving is

Osmosis

is the diffusion of water through a semipermeable membrane

Osmosis  Osmosis

is used by plants to lift water upward. All the plants cells must do is maintain a higher solute concentration inside their cells.

Osmosis

can pull water into of a cell if the cell is placed in an environment with a lower solute concentration

Hypotonic Solutions Hypotonic

means lower solute concentration  animal cells can rupture

in hypotonic environments  plant cells are protected from rupture by their strong cell walls

Osmosis

can also pull water out of a cell if the cell is placed in an environment with a higher solute concentration

Hypertonic Solutions Hypertonic

means higher concentration of solutes  A cell placed in a hypertonic

environment will lose water and shrink.  Plant cells plasmolyze when placed in very salty water.

Isotonic Solutions Isotonic

means balanced

 Cells in an isotonic environment

experience no net flow of water due to osmosis.  The water flowing in is balanced by the water flowing out

Red Blood Cells in a Range of

Summary  Hypertonic

= higher = dehydrating environment, cells shrink  Hypotonic = lower = bloating environment, cells swell  Isotonic = equal =homeostatic environment, cells “happy”

Hypertonic, Hypotonic, and Isotonic Examples  Solution  Quick

Examples

Osmosis Movie

Experiment Videos  Iodine

Ziplock Experiment

 Lettuce  Egg

Experiment

Experiment