Hydrophilic

Hydrophobic

Hydrophilic

Cell Membrane Structure

Structure of Cell Membrane

Protein

Protein

Protein

Cytoskeleton

_______

____________

• Energy is not needed for movement of materials across membrane

• The process by which molecules of a substance move from areas of higher concentration to areas of lower concentration–Ex. Air freshener, perfume

• Equilibrium occurs when the concentrations of the

substances on both sides of the membrane are the same

• Permeability the ability of a substance to diffuse

across a membrane• Selective Permeability only allowing certain substances to

pass through the membrane

• Diffusion of water molecules through a selectively permeable membrane

• Water tends to move across a membrane from a dilute solution (more water) into a concentrated solution (less water)

http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf

• Isotonic solution concentration of water is the same inside and

outside of the cell, so equal movement of water occurs

http://www.stephsnature.com/lifescience/osmosisanimations.htm

• Hypertonic solution concentration of water is higher inside the cell, so

water moves out of the cell and the cell shrinks

http://www.stephsnature.com/lifescience/osmosisanimations.htm

Hypotonic solution-concentration of water is lower inside the cell, so water moves into the cell and plant cells swell, but animal cells will burst

Example:

http://www.stephsnature.com/lifescience/osmosisanimations.htm

• Molecules are carried across a membrane in the direction of lowest concentration by a carrier protein (still passive transport – no energy needed)

• http://www.d.umn.edu/~sdowning/Membranes/diffusionanimation.html

• An energy-requiring process that enables material to move across a cell membrane against a concentration difference (from low to high)

http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter5/primary_active_transport.html

(once on website – press loop to run it in a loop)

• Process of taking materials into the cell by infolding the cell membrane (forming a pocket)

1. Phagocytosis - when large particles are taken into the cell

ex. Amoebas eatinghttp://www.stolaf.edu/people/giannini/flashanimat/

cellstructures/phagocitosis.swf

2. Pinocytosis - when liquid is taken into the cell

• When large molecules are expelled (removed) from the cell; usually wastes

http://www.stanford.edu/group/Urchin/GIFS/exocyt.gif

Diffusion & Osmosis Activity1) In figure 1, where is the area of high concentration of

ink? • in the middle/bottom of the beaker

2. In figure 2, draw what happens after you add ink to water.

3. What process have you shown on your model? • Diffusion

4. One side of the beaker in Figure 3 contains a dissolved substance, and the other side does not. Which side of the beaker has the highest concentration of water?

• Right side

5. In Figure 3, draw an arrow across the membrane showing the direction that water will tend to move.

6. What process is shown in this model?

• Osmosis

7. If the membrane in the beaker were impermeable, would the concentration of salt parts on either side of the membrane change?

• No because impermeable means nothing can move

8. Suppose you did the experiment in Figure 3 with sugar instead of salt. Would the results be similar? Explain.

• Yes because sugar and salt are similar molecules

2% salt0% salt 10% salt 2% salt

9. Is the concentration of water higher in Beaker B or in the cellophane bag? •In the bag

10. What would happen if you put the bag in Beaker B? Would the concentration of salt in the bag stay the same? Why or why not? •Water would move out of the bag•No, the concentration of salt would actually increase in the bag

11. If you put the bag in Beaker A, in which direction would the water move? •Into the bag

12. If you put the bag in Beaker C, would the concentration of salt in the bag change? Explain. •No, because they are the same (already at equilibrium)

13. In the space below, draw diagrams showing the cellophane bag inside each of the three beakers. Draw arrows to show the direction of water into or out of the bag.

2% salt 2% salt 2% salt

Hypotonic Hypertonic Isotonic

10% salt 2% salt0% salt