1. Cell Transport / Membrane Notes
It is the job of the plasma membrane to be a boundary that regulate what enters and leaves the cell. This model of a membrane is called the fluid-mosaic model because it is a combination (mosaic) of molecules suspended in a fluid-like framework.

2. Note: 3 of the 4 biomolecules comprise the membrane.

3. Parts of the Plasma Membrane
Phospholipid bilayer – main component
Phosphate head – hydrophilic (water-loving), water soluble – dissolves in water
Lipid tails – hydrophobic (fear of water), water insoluble – does NOT dissolve in water

4. Protein - protein channels for transport
Carbohydrates - identification markers- can be attached to phospholipid or protein
Cholesterol - stabilizes the membrane

5. Movement through Cell Boundaries: Selectively Permeable Membrane
The membrane is selectively or semi-permeable – some materials can pass thru, others cannot
(= membrane is impermeable to them).
Permeability depends on:
particle size – small molecules such as O2, CO2 and H2O pass through
shape of molecules – for protein channels
charge of ions (some ions are repelled)

6. Passive Transport
Requires no energy (E) because it relies upon random particle movements.
Goes with concentration gradient = (difference in concentration on either side of membrane) until equilibrium is reached (same concentration on both sides of membrane)
Molecules are constantly moving, so they will move naturally with the concentration gradient.

7. 3 Types of Passive Transport
Diffusion – any material, except H2O moving from high to low concentration thru bilayer

8. Passive Transport continued…
2. Facilitated Diffusion – uses protein channels to enter / leave cells
ex: glucose can only enter this way
It is fast, specific and requires no energy

9. Passive Transport continued…
Osmosis – the diffusion of H2O
Only water moving from a high to a low concentration until solution reaches equilibrium
Osmotic pressure – pressure exerted on membrane when water moves across
Note: Penicillin works because it weakens cell walls, osmotic pressure increases and causes bacteria membranes to burst.

10. Osmosis

11. Solutions (terms only apply to water movement = osmosis)
Isotonic – equal conc. of solute molecules on either side of membrane; no net movement of water
Hypertonic – more solute outside of cell, water moves out of cell, cell shrinks; in plants it causes plasmolysis (loss of turgor pressure)
Hypotonic – less solute outside of cell, water enters cell, cell could burst.

12. Osmosis: Maintaining Homeostasis
- the process by which organisms maintain a relatively stable, internal environment

15. http://highered. mcgraw-hill

16. Cell Water Balance

17. Active Transport
Molecules move against the concentration gradient; from low concentration to high concentration
Requires energy (E) = ATP
ATP (adenosine triphosphate) is the E molecule
chemical produced and used by your cells

18. Bulk Transport – Vesicles / Vacuoles
Endocytosis – cells take in particles by membrane forming a “pocket” - a vesicle / vacuole
Exocytosis – releasing materials from cells in vesicles that fuse with membrane
ex: vesicles of hormones, enzymes, wastes
ex: vacuoles removing water or wastes; contractile vacuole in protist pump out extra water
Requires ATP!