1. 1. Structure of Plasma membrane
* Two-layered structure:
lipid bilayer
*Made of lipid molecules
with protein molecules in
the lipid layer.
**PROTEINS aid in the movement of materials through the membrane

2. extracellular fluid (watery environment) phospholipid hydrophilic
heads
hydrophobic
tails
bilayer
Figure: 03-00UN02
Title:
Phospholipid bilayer.
Caption:
hydrophilic
heads
cytoplasm
(watery environment)

3. Polar Head Non-Polar Tails tails (hydrophobic) head (hydrophilic)
Figure: 03-00UN01
Title:
A phospholipid.
Caption:
A phospholipid has a polar hydrophic head and a pair of nonpolar hydrophobic tails.
tails
(hydrophobic)
head
(hydrophilic)

4. * Bilayer can be considered a liquid
FLUID MOSAIC MODEL: plasma membrane : made up of molecules that are free to flow among one another.
Kinds and arrangements of proteins + lipids vary from one membrane to another and give each type of membrane specific permeability properties.

5. Fluid Mosaic Model of the cell membrane
Polar heads love water & dissolve.
Fluid Mosaic Model of the cell membrane
Membrane movement animation
Non-polar tails hide from water.
Carbohydrate cell markers
Proteins

6. Structure of the Cell Membrane
Outside of cell
Carbohydrate
chains
Proteins
Lipid
Bilayer
Transport
Protein
Phospholipids
Animations
of membrane structure
Inside of cell
(cytoplasm)
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7. 1. Maintaining a BALANCE in a CELL
Cells Maintain HOMEOSTASIS : internal balance
Semi Permeable : allows
some materials to pass through
membrane while rejecting others.

8. Diffusion
Movement of molecules high concentration to lower concentration
Example: skunk, perfume, night after a dinner at Taco Bell!

9. Diffusion animation 2 Dye molecules diffuse into the water; water
into the dye.
3 Both dye molecules
and water molecules
are evenly dispersed.
1 A drop of dye is
placed in water.
drop of dye
Figure: 03-02
Title:
Diffusion of a dye in water.
Caption:
pure water
Diffusion animation

10. Osmosis
The diffusion of Water from areas of high concentration to areas of low concentration
Animation: How Osmosis Works

11. Transport across membranes
Passive transport of water by Osmosis
a. Isotonic
b. Hypertonic
c. Hypotonic

12. Isotonic Solution:
Solution concentration of water (solvent) outside of the cell is the same as concentration inside the cell (Animal cell normal / plant flaccid)

13. Hypotonic Solution: concentration of water (solvent) outside the cell is higher than concentration inside the cell. Water rushes into the cell!
Ø Turgor pressure: Pressure that builds in a plant cell as a result of osmosis. Makes a plant cell firm. (Turgid) Plant cells are healthiest in a hypotonic environment.
Ø Lysed: pressure builds in animal cell (burst)

14. Hypertonic Solution: concentration of water (solvent) outside cell is lower than concentration inside the cell. Water rushes out of the cell!
ØØ Plasmolysis: loss of water from within a plant cell, causing cytoplasm to shrink, pulling inner plasma membrane away from cell wall. (wilting of plants)
ØØ Crenation: (crenates: shrinks) animal cell loses water and it shrinks (collapses)

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

17. (b) hypertonic solution (c) hypotonic solution
10 micrometers
(a) isotonic solution
(b) hypertonic solution
(c) hypotonic solution
Figure: 03-05
Title:
The effects of osmosis.
Caption:
Red blood cells are normally suspended in the fluid environment of the blood. (a) If red blood cells are immersed in an isotonic salt solution, which has the same concentration of dissolved substances as the blood cells do, there is no net movement of water across the plasma membrane. The red blood cells keep their characteristic dimpled disk shape. (b) A hypertonic solution, with too much salt, causes water to leave the cells, shriveling them up. (c) A hypotonic solution, with less salt than is in the cells, causes water to enter, and the cells swell.
equal movement of water
into and out of cells
net water movement
out of cells
net water movement
into cells

18. 5. PASSIVE TRANSPORT: No energy required for this to happen
Passive transport : movement of substances across plasma membranes without additional energy
Facilitated diffusion: diffusion of materials across a plasma membrane by transport (channel) proteins.

19. Active Transport : gradient from low to high. Energy is required.
6. ACTIVE TRANSPORT: Requires energy in the form of ATP
Active Transport : gradient from low to high. Energy is required.
Proteins throughout the membrane are “carriers” used for this purpose.

20. Sodium-potassium pump
Na  out K  in
ACTIVE TRANSPORT = ATP
Na+ ions: moved out of cell
K+ ions: moved by the same carrier into the cell
(This process is important in nerve and muscle function.)

21. Animation of transport across a membrane

22. 7. TRANSPORT of LARGE PARTICLES
· Endocytosis (Endo = In): cell surrounds and takes in material from environment. Material does not pass through the membrane; instead, it is engulfed and closed by a portion of membrane and cytoplasm.
Ø Pinocytosis: water
Ø Phagocytosis: food/ minerals/ large particles
· Exocytosis (Exo = Out): transport of materials out of cell across cell membrane.

23. Exocytosis
Outside of the cell
Inside of the cell

24. (extracellular fluid)
Animated Review of Phagocytosis, Pinocytosis and Receptor Mediated Endocytosis.
Click on Active Transport, watch the brief overview of Active Transport and then click on Endocytosis in the bar below the animation
pinocytosis
(extracellular fluid) 1 3 3 2
vesicle containing
extracellular
fluid
(cytoplasm)
Figure: 03-07
Title:
Two types of endocytosis.
Caption:
(a) To capture drops of liquid, a dimple in the plasma membrane deepens and eventually pinches off as a fluid-filled vesicle, which contains a random sampling of the extracellular fluid. (b) Pseudopodia encircle an extracellular particle. The ends of the pseudopodia fuse, forming a large vesicle that contains the engulfed particle.
cell
(b)
phagocytosis
food particle
pseudopod 1 2 3
particle
enclosed in vesicle