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
3. Polar Head
Non-Polar 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. Polar heads Fluid Mosaic Model
love water & of the cell
dissolve. membrane
Non-polar Membrane
movement
tails hide animation
from water.
Carbohydrate cell
markers
Proteins
6. Structure of the Cell Membrane
Outside of cell
Carbohydrate
Proteins chains
Lipid
Bilayer
Transport
Protein Phospholipids
Animations
of membrane Inside of cell
structure (cytoplasm)
Go to
Section:
7. 1. Maintaining a BALANCE in a
CELL
Cells Maintain HOMEOSTASIS : internal balance
Selective permeability : 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. 2 Dye molecules
diffuse into the 3 Both dye molecules
1 A drop of dye is water; water and water molecules
placed in water. molecules diffuse are evenly dispersed.
into the dye.
drop of dye
pure water
Diffusion animation
10. Osmosis
The diffusion of
Water from areas
of high
concentration to
areas of low
concentration
Animation: How Osmosis Works
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!
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.
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!
Plasmolysis: loss of water from within a plant cell,
causing cytoplasm to shrink, pulling inner plasma membrane
away from cell wall. (wilting of plants)
Crenation: (crenates: shrinks) animal cell loses water
and it shrinks (collapses)
15.
16. What type of solution are these cells in?
A B C
Hypertonic Isotonic Hypotonic
17. 10 micrometers
(a) isotonic solution (b) hypertonic solution (c) hypotonic solution
equal movement of water net water movement net water movement
into and out of cells out of cells 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. 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. 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.
Pinocytosis: water
Phagocytosis: food/ minerals/
large particles
• Exocytosis (Exo = Out):
transport of materials out of cell
across cell membrane.
23. (a)
Animated Review of Phagocytosis,
Pinocytosis and Receptor Mediated
pinocytosis
(extracellular fluid) Endocytosis.
Click on Active Transport, watch the
brief overview of Active Transport and
1 then click on Endocytosis in the bar below
the animation
3
2
vesicle containing
extracellular
(cytoplasm) fluid
cell (b)
phagocytosis
food particle
pseudopod
1 2 3
particle
enclosed in vesicle
Figure: 03-00UN01 Title: A phospholipid. Caption: A phospholipid has a polar hydrophic head and a pair of nonpolar hydrophobic tails.
Figure: 03-02 Title: Diffusion of a dye in water. Caption: Diffusion of a dye in water.
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.
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.