1. Cell Membrane Structure & Cell Transport Notes

2. Cell Membrane Fluid mosaic model
Mosaic  mixed composition primarily of phospholipids and proteins.
Fluid  it is not a solid layer; it is selectively permeable.
Phospholipids are arranged in a bilayer
Proteins on the surface (act as markers)
Proteins embedded in the bilayer (transport)

3. Structure of Phospholipids
Hydrophilic, Water-Loving, & Polar
Phospholipids contain…….
hydrophilic phosphate head &
2 hydrophobic fatty acid tails
Hydrophobic, Water-Fearing, & Non-Polar

4. Phospholipid Bilayer
Forms due to the polarity (opposite ends) of the phospholipids
Phosphate heads (polar)
Close to the water of the cytoplasm and/or water inside the cell
Face outward
Fatty acid tails
Face inward to avoid being near water
Creates a barrier b/w inside and outside of the cell

5. Phospholipid Bilayer Phosphate heads one layer of phospholipids
Fatty acid
Tails
Phosphate heads

6. Transport Proteins Span the phospholipid bilayer
Interior is able to open to both sides
May change shape when they interact with solute
Move water-soluble substances across a membrane
May be passive or active

7. Cell Membrane Structure

8. Cell Membrane Structure

9. Cell Membrane Function
Creates a barrier b/w inside & outside of cell
Proteins that pass through the entire bilayer act a channel to transport large substances OR transport substances against their gradients

10. Cell Membrane: Selectively Permeability
CAN PASS THRU MEMBRANE
O2 and CO2
H2O and glucose (sugar)
CANNOT PASS THRU MEMBRANE
Ions (charged)-like salt
Large molecules

11. Cell Transport Passive Transport Active Transport Uses no ATP (energy)
High  Low Concentration
Down the concentration gradient
Ex.
Simple diffusion
Osmosis
Facilitated Diffusion
Active Transport
Uses ATP (energy)
Low  High Concentration
Against the concentration gradient
Ex.
Transport/Carrier Protein
Endocytosis
Exocytosis

12. Types of Passive Transport
Simple Diffusion  HL; no E; CO2 and O2
Osmosis  HL; no E; H2O
Facilitated Diffusion  HL; no E; glucose thru a transport protein

13. Simple Diffusion:
A drop of dye inters a bowl of water. Gradually, the dye molecules become evenly dispersed through the molecules of water.

14. Factors Affecting Diffusion Rate
Steepness of concentration gradient
Steeper gradient  faster diffusion
Molecular size
Smaller molecules faster diffusion
Temperature
Higher temperature  faster diffusion

15. Concentration Gradients
Molecules ALWAYS move down their concentration gradient in passive transport
From high  low

16. Osmosis – A Type of Passive Transport
Net movement of water from high  low
Between two regions separated by a selectively permeable membrane
Red dot = H20
Blue Dot = Solute

17. How will Water Move?
Water will always move from where there is more water to where there is less water

18. Tonicity -Iso=same -Hypo=HippO -Hyper=out
H2O in cells swells H2O moves out
and out with H2O (go OUTside and play if you are hyper)!

19. 2% sucrose
solution
10%
sucrose
solution 2%
sucrose solution
distilled water
Hypotonic
Conditions
Hypertonic
Conditions
Isotonic
Conditions

20. Turgor Pressure & Plasmolysis
Occurs in plants b/c of the cell wall
Turgor Pressure
Occurs when water moves from hypotonic environment into the hypertonic plant cell
Cell membrane expands and pushes against the cell wall creating pressure
Plasmolysis
Occurs when water moves from hypotonic plant cell to a hypertonic environment
Cell membrane shrivels (plants wilts & may die)

21. Turgor Pressure & Plasmolysis

22. Facilitated Diffusion – A Type of Passive Transport
Using a protein to move a substance from where it is in a high concentration to where it is in a low concentration

23. Active Transport Uses energy (ATP)
Moves from low to high concentration
Against concentration gradient
Several types:
Transport Protein
Endocytosis & Phagocytosis
Exocytosis

24. Transport Protein – A Type of Active Transport
Na+/K+ Pump

25. Endocytosis – A Type of Active Transport
Moves bulk items that are larger

26. Endocytosis
A patch of cell membrane forms a vesicle that sinks into the cytoplasm.
Cell takes “in” molecules
A special type is called “phagocytosis”

27. Phagocytosis or Cell Eating
Active (requires ATP)
Changes in microfilaments change cell shape to form a bulging lobe that surrounds target and forms a vesicle
edible
bacterium
amoeba

28. Exocytosis – A Type of Active Transport
A cytoplasmic vesicle fuses with the cell membrane and its contents are released outside.
Cell membrane
cytoplasm