1. Cellular Transport

2. I. Introduction to Cell Transport
All living cells need to be able to:
Take in oxygen and nutrients
Get rid of wastes
Cell transport= moving materials in and out of a cell
The cell membrane separates the inside of the cell from the outside.
It allows some things to enter and blocks other things

3. A. Cell Membrane Structure
Phospholipid Bilayer- double layer of phospholipids enclosing the cell
Each phospholipid is made of a glycerol bonded to 2 fatty acids and a phosphate group.
Phosphate group is polar (hydrophilic)
Fatty acids are non-polar (hydrophobic)
Bilayer:
Exterior and interior surface: polar heads
Internal part: non-polar tails

4. Phospholipid Bilayer

5. B. Membrane Proteins Proteins embedded in or thru the lipid bilayer.
Integral proteins- are embedded in the lipid bilayer.
Peripheral proteins- are loosely held on the surface.

6. B. Membrane Proteins
Membrane proteins can be used to transport materials thru the membrane, serve as chemical signals or receptors of chemical signals.
Membranes also can contain cholesterol (animal cells) and glycoproteins containing carbohydrates.

7. C. Fluid Mosaic Model
Describes the cell membrane as a fluid rather than a solid.
Phospholipids and some proteins are able to move laterally within each other.
This creates a mosaic that is able to change its shape and form.

8. D. Selective Permeability
Due to its structure, polarity, and proteins, the cell membrane regulates what can pass in or out of the cell.
this maintains a stable internal environment (homeostasis)
Factors that determine a substances’ ability to pass thru the membrane:
Size
Shape
Polarity
Charge
Chemical make-up

9. II. Movement Through the Membrane

10. A. Solution Lingo Solution= combination of solute and solvent
Solute= Substance being dissolved
Solvent= thing substance is dissolved in
Universal solvent= water
*Solute dissolves in the solvent
Concentration Gradient= A difference in concentrations within a system

11. B. Particle Movement
Brownian motion- constant random motion of all particles.

12. C. Passive Transport
Movement across the membrane requiring no additional energy from the cell.
Types:
Diffusion
Facilitated Diffusion
Osmosis

13. 1. Diffusion
Net movement of particles from areas of high concentration to low concentration.
Particles will have NET movement towards low concentration until concentration is equal throughout the system (Dynamic Equilibrium)
Particles will continue to move, but there will be no NET movement.

14. Diffusion Animation

16. 2. Facilitated Diffusion
Diffusion of particles thru the cell membrane w/ the assistance of membrane proteins.
Carrier proteins
Integral proteins that change shape to move large molecules thru the lipid bilayer.

17. Facilitated diffusion of Glucose

18. Ion channels
integral proteins that provide a tube for dissolved ions to pass thru the lipid bilayer.
Ex. Na+ ion channel

19. Important!
***movement thru the proteins involves kinetic E, but no cellular E because the particles are moving with the concentration gradient.

20. 3. Osmosis The diffusion of water across a membrane.
particles dissolved in water are solutes; water is the universal solvent.
water will have a net movement (opposite of solute movement)
Types of solutions:
Hypertonic solution- aqueous solution with a higher concentration of solute than the cell.
particles will move into the cell
water will rush out of the cell
Causes plasmolysis (wilting) in plant cells.

21. ii. Hypotonic Solution
Solution with a lower concentration of solute than the cell.
particles will move out of the cell
water will move into the cell causing it to swell
causes Turgor Pressure in plant cells
Can cause cytolysis (bursting) of animal cells

22. iii. Isotonic solution
Equal concentration of solute in the solution and the cell.
net movement of water and solute is equal
cell is in dynamic equilibrium w/ the solution

23. Osmosis in plant cells

24. Osmosis of red blood cells

25. Osmotic pressure
Which way will the water move?

26. How Cells Deal with Osmosis
How do cells like paramecium that live in water, not blow up?
Contractile vacuoles – organelles that remove water from the cell.

27. D. Active Transport
Movement of substances against the concentration gradient. (low to high)
Requires the use of cellular E.
Necessary to maintain homeostasis in non-isotonic environments

28. Carrier Proteins (pumps)
Integral proteins that force particles against the concentration gradient
ATP (E) is used to change the shape of the protein.
ex. Na+/K+ ion pump
Uses ATP to keep a high concentration of Na+ outside the cell and K+ inside the cell.
Keeps an unbalanced charge on opposite sides of the membrane allowing for the transmission of electrical signals.

29. Na+/K+ ion pump

30. Endocytosis
Process by which cells ingest large particles or large amounts of solution.
membrane pinches off around material creating a vacuole which often joins w/ lysosomes to digest the material.
Types
Pinocytosis- ingesting large amounts of fluid or solutes.
Phagocytosis- ingesting large particles or whole cells.
ex. White blood cells, Ameoba

31. Exocytosis Release of large particles from the cell
excretory vesicles carrying proteins, wastes or other large particles fuse w/ the cell membrane releasing the material extra-cellularly.

32. Endocytosis and Exocytosis

33. Endocytosis vs. Exocytosis
Which is endocytosis? Exocytosis?

34. Questions Write out the questions and answer in complete sentences.
How is selective permeability related to passive and active transport?
Describe two differences between active and passive transport.