1. 7-3 Cell Transport

2. REVIEW
Regulates what enters and leaves the cell
Protects and supports the cell
Composed of
Lipids = bilayer
Proteins = channels
Carbs = identification cards

3. Different types of movement
Passive Transport
Diffusion
Osmosis
Facilitated Diffusion
Active Transport
Membrane Pumps
Endo/Exocytosis

4. PASSIVE TRANSPORT – Diffusion “passive” = no energy required
Molecules in Motion
Molecules are in constant motion
Move from a region where they are more numerous (high concentration) to where they are less numerous (low concentration)
Want to reach a state where molecules are spread out evenly = EQUILIBRIUM

5. PASSIVE TRANSPORT – Diffusion “passive” = no energy required
Diffusion – the process by which molecules of a substance move from areas of higher concentration of that substance to areas of lower concentration
Factors that contribute to movement of substances:
Unequal concentrations
Permeability
The cell membrane is selectively permeable – allowing some things to cross while others cannot

6. 2. PASSIVE TRANSPORT - Osmosis
Most molecules cannot dissolve in the lipid bilayer of the cell; therefore, they cannot pass through - BUT – WATER CAN…
Osmosis – diffusion of water across a selectively permeable membrane

7. Osmotic pressure – the force exerted by osmosis
Water will pass through the membrane from a area of high water concentration to an area of low water concentration
There is a net movement of water from where there is less solute to where there is more solute (in an attempt to dilute it)
Osmotic pressure – the force exerted by osmosis
Types of tonicity (the ability of a substance to draw water towards it)

8. Isotonic Solution “Iso” = the same
Water will move both ways in equal amounts
Why is important that contact lens solution is isotonic?

9. Hypotonic Solution "Hypo" = less
Less solute (salt) molecules outside the cell
Water will move in both directions
BUT more water will move into the cell causing it to grow larger (cytolysis)
In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid (turgid), the cell wall keeps the plant from bursting
In animal cells, the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES (only on paramecium) will pump water out of the cell to prevent this

10. Hypertonic Solution "Hyper" = more
More solute (salt) molecules outside the cell
Water will move in both directions
BUT more will move out of the cell causing it to shrink (plasmolysis)
In plant cells, the central vacuole loses water and the cells shrink, causing wilting (loss of turgor pressure)
In animal cells, the cells shrink
In both cases, the cell may die
Why is it dangerous to drink sea water?
This is also why "salting fields" was a common tactic during war, it would kill the crops in the field, thus causing food shortages

11. Which type of solution is it? A B C

13. 1. What type of solution is this “cell” in?
a: hypotonic solution
2. What will happen to this “cell” over time?
a: the cell will expand and possibly burst = CYTOLYSIS

14. 3. PASSIVE TRANSPORT - Facilitated Diffusion
No energy required
Carrier proteins transport molecules across the membrane (from high to low concentrations)
Molecules may be too big or cells may need to get the molecules quickly

16. 4. ACTIVE TRANSPORT Requires energy (usually ATP)
Move molecules against the concentration gradient – the opposite direction of passive transport

17. 4. ACTIVE TRANSPORT - Membrane Pumps
Transport macromolecules move molecules across the cell membrane
Requires ENERGY
Examples – calcium, potassium, sodium ions

19. 5. ACTIVE TRANSPORT – Endocytosis vs. Exocytosis
Endocytosis – taking materials into the cell by infoldings of the cell membrane
Phagocytosis – when large particles (food, microorganisms) are taken into the cell
Pinocytosis – when liquids or relatively small particles (solutes) are taken into the cell
Receptor-mediated endocytosis

21. Exocytosis – when large molecules are removed from the cell
Contractile vacuoles – water is pumped out of the cell so it doesn’t burst

22. concentration gradient facilitated diffusion
active transport
concentration gradient
energy
facilitated diffusion
particles/water