1. Cell (Plasma) Membrane & Cell Transport

2. 7-3 Cell Boundaries
All cells are surrounded by a thin, flexible barrier known as the cell membrane.
Many cells also produce a strong supporting layer around the membrane known as a cell wall.
Copyright Pearson Prentice Hall

5. Homeostasis Balanced internal condition of cells
Also called equilibrium
Maintained by plasma membrane controlling what enters & leaves the cell

6. Functions of Plasma Membrane
Protective barrier
Regulate transport in & out of cell (selectively permeable)
Allow cell recognition
Provide anchoring sites for filaments of cytoskeleton
Provide a binding site for enzymes
Interlocking surfaces bind cells together (junctions)
Contains the cytoplasm (fluid in cell)

7. Phospholipid Makes up the cell membrane – 2 layers bilayer
Phosphate Head – hydrophilic – water loving
Fatty acid Tail – hydrophobic – water fearing
Makes the membrane “Selective” in what crosses

9. Semipermeable Membrane
Small molecules and Hydrophobic molecules flow easily through.
Examples: Oxygen, Carbon dioxide and Water

10. Semipermeable Membrane
Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own.

11. Types of Cell Transport
Passive and Active

12. Passive Transport Requires NO energy
The Plasma Membrane
6/2/2018
Passive Transport
Requires NO energy
Molecules move from area of HIGH to LOW concentration
G. Podgorski, Biol. 1010

13. The Plasma Membrane
6/2/2018
DIFFUSION
Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY
Moves DOWN the concentration gradient
G. Podgorski, Biol. 1010

14. Diffusion of Liquids

15. The Plasma Membrane
6/2/2018
Simple Diffusion
Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out.
G. Podgorski, Biol. 1010

16. Facilitated Diffusion
The Plasma Membrane
6/2/2018
Facilitated Diffusion
Doesn’t require energy
Uses transport proteins to move high to low concentration
Examples: Glucose or amino acids moving from blood into a cell.
G. Podgorski, Biol. 1010

18. Diffusion across a membrane Semipermeable membrane
The Plasma Membrane
6/2/2018
Osmosis
Diffusion across a membrane
Diffusion of water across a membrane
Moves from HIGH water potential (low solute) to LOW water potential (high solute)
Semipermeable membrane
G. Podgorski, Biol. 1010

23. Active Transport Requires energy or ATP
The Plasma Membrane
6/2/2018
Active Transport
Requires energy or ATP
Moves materials from LOW to HIGH concentration
AGAINST concentration gradient
G. Podgorski, Biol. 1010

25. Example of Active Transport: Sodium-Potassium Pump

26. Endocytosis – Brings into cell

27. Pinocytosis Called “Cell Drinking” Involves LIQUIDS
The Plasma Membrane
6/2/2018
Pinocytosis
Called “Cell Drinking”
Involves LIQUIDS
G. Podgorski, Biol. 1010

28. Phagocytosis – “Cell Eating” – Involves SOLIDS

29. Exocytosis – Releases from the Cell