1. Cellular Transport Notes

2. About Cell Membranes All cells have a cell membrane Functions:
Controls what enters and exits the cell to maintain an internal balance called homeostasis
Provides protection and support for the cell

3. About Cell Membranes (continued)
Structure of cell membrane
Lipid Bilayer -2 layers of phospholipids
Phosphate head is polar (water loving)
Fatty acid tails non-polar (water fearing)
Proteins embedded in membrane
Steroids and cholesterol are embedded within the cell membrane.They provide support and flexibility.
Phospholipid
Lipid Bilayer

4. Fluid Mosaic Model of the cell membrane States that the membrane is in constant motion
Polar heads love water & dissolve.
Non-polar tails hide from water.
Carbohydrate cell markers
Proteins

5. About Cell Membranes (continued)
4. Cell membranes have pores (holes) in it
Selectively permeable: Allows some molecules in and keeps other molecules out
The structure helps it be selective!
Pores

6. Cell Membrane

7. Cholesterol in the Membrane

8. Structure of the Cell Membrane
Outside of cell
Carbohydrate
chains
Proteins
Lipid
Bilayer
Transport
Protein
Phospholipids
Inside of cell
(cytoplasm)
Animations
of membrane structure
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9. Cell Transport There are three types of cellular transport
Passive Transport
Active Transport
Cytosis

10. Types of Cellular Transport
Animations of Active Transport & Passive Transport
high
low
Weeee!!!
Passive Transport
cell doesn’t use energy
Diffusion
Facilitated Diffusion
Osmosis
Active Transport
cell does use energy
Protein Pumps
Endocytosis
Exocytosis
high
low
This is gonna be hard work!!
Cytosis

11. Passive Transport: 1. Diffusion
Simple Diffusion Animation
Passive Transport: 1. Diffusion
Diffusion: random movement of particles from an area of high concentration to an area of low concentration.
(High to Low)
Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out.

12. What determines the rate of diffusion? There 4 factors:
The steepness of the concentration gradient. The bigger the difference between the two sides of the membrane the quicker the rate of diffusion.
Temperature. Higher temperatures give molecules or ions more kinetic energy. Molecules move around faster, so diffusion is faster.
The surface area. The greater the surface area the faster the diffusion can take place. This is because the more molecules or ions can cross the membrane at any one moment.
The type of molecule or ion diffusing. Large molecules need more energy to get them to move so they tend to diffuse more slowly. Non-polar molecules diffuse more easily than polar molecules because they are soluble in the non polar phospholipid tails.

13. Passive Transport
The diffusion of water is called OSMOSIS.

14. Passive Transport - Osmosis
A good way to remember which way water will move is to remember that the water will ALWAYS move TOWARDS the solutes (salt).

15. Passive Transport: 3. Osmosis
Osmosis animation
3.Osmosis: diffusion of water through a selectively permeable membrane
Water moves from high to low concentrations
Water moves freely through pores.
Solute (green) to large to move across.

16. Passive Transport
We have special names for the different types of situations where osmosis occurs in cells.

17. Passive Transport
We have special names for the different types of situations where osmosis occurs in cells.

18. Hypotonic Solution
Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water)
Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!

19. Hypertonic Solution
Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water)
shrinks
Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!

20. Isotonic Solution
Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell.
Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)

21. B C A What type of solution are these cells in? Hypertonic Isotonic
Hypotonic

22. Summary
Isotonic Solutions are those where the concentration of the solution EQUALS the concentration of the cell.
Hypertonic Solutions are those where the concentration of the solution is MORE than the concentration of the cell.
Hypotonic Solutions are those where the concentration of the solution is LESS than the concentration of the cell.

23. What is the solution? 40% Salt 10% Salt 15% Salt 10% Salt 40% Salt
Hypotonic
Hypertonic
Isotonic

24. What is the cell? 40% Salt 10% Salt 15% Salt 10% Salt 40% Salt
Hypertonic
Hypotonic
Isotonic

25. In osmosis, goes towards the !
Remember!
In osmosis, goes towards the !

26. Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer)
Passive Transport: Facilitated Diffusion A B
Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane
Transport Proteins are specific – they “select” only certain molecules to cross the membrane
Transports larger or charged molecules
Facilitated diffusion (Channel Protein)
Diffusion (Lipid Bilayer)
Carrier Protein

27. Passive Transport: 2. Facilitated Diffusion
Glucose
molecules
Cellular Transport From a-
High
High Concentration
Cell Membrane
Low Concentration
Protein
channel
Low
Transport Protein
Through a 

28. Facilitated Diffusion:
Molecules will randomly move through the opening like pore, by diffusion. This requires no energy, it is a PASSIVE process. Molecules move from an area of high concentration to an area of low conc.

30. Active Transport
Active transport is when the cell membrane “imports” or “exports” substances that are needed that do not travel by diffusion.
Usually, this means obtaining substances against the concentration gradient
Substances go from areas of LOW concentration to areas of HIGH concentration

31. Active Transport

32. Types of Active Transport
Sodium Potassium Pumps (Active Transport using proteins)
1. Protein Pumps -transport proteins that require energy to do work
Example: Sodium / Potassium Pumps are important in nerve responses.
Protein changes shape to move molecules: this requires energy!

33. Active Transport Active Transport uses energy called ATP.
Active Transport = ATP
Accomplished by the proteins embedded within the cell membrane.

34. Active Transport
The lack of efficient pumps can be classified as a disease.
Sodium Deficiency can cause muscle spasms, and Liddie's Syndrome.
Potassium deficiencies can cause an irregular heart beat, epileptic seizures in infancy, and deafness.
 Examples of active transport include:
Kidney's removing sodium
Thyroid obtaining iodine
Gills removing salt from water
Plants obtaining minerals through the roots.

35. Summary

36. Cytosis: A type of Active Transport
Large amounts of some substances can be taken in and out of a cell directly by the membrane.
Endocytosis
Exocytosis

37. Types of Active Transport
Endocytosis:
Uses energy (ATP)
Cell membrane in-folds around food particle
Endocytosis of large particles is called phagocytosis, “cell eating”
Endocytosis of small particles is called Pinocytosis, “cell drinking”
forms food vacuole & digests food
This is how white blood cells eat bacteria!

38. Phagocytosis
Your white blood cells can keep you healthy by using PHAGOCYTOSIS
The LYSOSOMES digest the bacteria cell and then spit it out of the cell.

39. Types of Active Transport
3. Exocytosis:
movement of material out of cytoplasm of the cell using ATP
membrane surrounding the material fuses with cell membrane (like endocytosis backwards)
how cells get rid of wastes
Endocytosis & Exocytosis animations

40. Vesicles and Vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell. Exocytosis is the term applied when transport is out of the cell.