Cell Membrane and Transport
On the left side of your IntNB,
draw the set-up of the
demonstration once it has been
explained to you.
Make an hypothesis as to which
direction the liquid will flow.
The plasma/cell membrane is selectively
permeable
~only certain substances are allowed to
pass through
What can and can not pass
through the membrane?
CAN PASS THROUGH
• Things that can
dissolve in fat
• Small molecules
• Water
CAN NOT PASS THROUGH
1. Things that can dissolve in
water
2. Large molecules
3. Ions: Molecules with plus
(+) or minus (-) charges
CH2OH
OH
What is an Isotonic Solution?
• [Water] inside cell =
[Water] outside cell
• Cell is at equilibrium
– Molecules are equally
distributed in end
• The amount of water
entering the cell = the
amount of water
leaving the cell
95%
water
95%
water
What is a hypotonic solution?
• A solution that has
MORE water, and
LESS solute
• The cell can lyse or
burst if left in a
hypotonic solution
100%
water
95%
water
What is a hypertonic solution?
• A solution that has
LESS water and MORE
solute
• The cell will dehydrate
90%
water
95%
water
What can pass through a
membrane? (p. 253)
Can pass through
Cannot pass
membrane
through membrane
Solubility?
Fat soluble
Water soluble
Size?
Small
Large
Charge?
Uncharged
Molecules
Ions (H+, Na+,
HCO3-, K+…)
The Plasma Membrane (p. 251)
Carbohydrate side chains
Glycoprotein
Proteins
Outside of Cell
Hydrophilic Region
Hydrophobic Region
Hydrophilic Region
Inside of Cell
Phospholipid
TEM of a red blood cell
There are three types…
No energy is used
[High]  [Low] (it’s the natural flow)
This means it goes down a concentration gradient
Passive Transport: Diffusion
[High]  [Low]
Passive Transport: Osmosis (Diffusion of water)
Osmosis
+
CH2OH
Facilitated Diffusion
OH
Passive Transport: Facilitated Diffusion
There are three types…
Energy is used
[Low]  [High]
This means it goes up or against a
concentration gradient
Active Transport: Protein Pumps
Protein Pumps
Protein Pumps: proteins use energy to pull or
pump materials into or out of the cell to
stockpile or store substances the cell needs
Different Types of Membrane
Proteins (page 252)
TRANSPORTERS
RECEPTORS
ENZYMES
SIGNAL/
RECOGNITION
Different Types of Membrane
Proteins (page 252)
signal/recognition
Enzymes
receptor
transporter
Active Transport: Endocytosis
Endocytosis
•
•
When cells engulf particles into the cell
2 types
1. Phagocytosis: When a cell wraps part of its
membrane around
a large particle
forming a “pocket”
or vesicle
2. Pinocytosis: The
same process,
but with smaller
particles or liquids
Active Transport: Exocytosis
Exocytosis
1. A vesicle carrying a
substance
2. fuses with the cell
membrane
3. and releases the
substance