Osmosis and Potatoes_ by sdfwerte

VIEWS: 227 PAGES: 10

									Osmosis and Potatoes!
                       Osmosis is the movement of
                       water molecules, across a
                       partially permeable
                       membrane, from a region of
Text book definition   high concentration of water to
                       a low concentration of water
o Osmosis has the following uses:

           It allows plants to take in water
           through their roots.

           It is used in kidney dialysis machines to
           filter the blood.
Remember!! A              A partially permeable
membrane controls
what goes in and out of   membrane is a membrane
the cell.
                          with holes in it small
Permeable means it        enough for only WATER
allows substances to
go through it.            to go through it. Big
                          molecules like glucose
                          can not fit through
                          See next slide…


Small molecules, such as water         Large molecules like sugar can not
can pass through it.                   pass through the membrane

                       Diagram shows the net flow of water
     Water        Sugar
                                      The water molecules pass both
                                      ways through the membrane

                                       The overall flow (net flow) of
                                       water molecules is from a
                                       region with lots of water
                                       molecules to region of less
                                       water molecules.

Lots of water   Few water molecules

The water moves into the sugar - rich region to fill it up with
water. The water moves as if to even up the concentration
either side of the membrane.
OSMOSIS is the movement of water molecules across
a partially permeable membrane.
The membrane only allows small molecules, e.g. water
to pass through it.
Large molecules e.g. glucose can NOT pass through
the membrane.
Water molecules move into the region where there are
less water molecules
The water acts to even up the concentration of water
either side of the membrane.
Using the above facts you should now be able to understand what
happens in the potato investigation

  What happens here?
    Pure Water

   In pure water the potato tubes swell, because water
   enters their cells by osmosis.

              Remember, potatoes are rich in starch – which
              is a complex sugar.
What happens here?

Solution                        Potato

 In rich sugar solution the potato
 tubes shrink, because water leaves
 the potato by osmosis.
If you would like to go over some of the points
   again , choose one of the options below.

                 BACK TO START
                   What is Osmosis?
        What is a partially permeable membrane?
           A partially permeable membrane
         Osmosis – what is actually happening?
               Potato tubes in pure water
           Potato tubes in sugar – rich water

To top