The Plasma Membrane:
Membrane transport
Megan White
Silver King
Haeran Yu
Interstitial Fluid
• Cells are bathed in interstitial fluid which is
d i d from
derived
f
the
h blood.
bl d This
hi fluid
fl id contains
i
amino acids, sugars, fatty acids, vitamins,
regulatory substances.
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Selectively Permeable
• Allows some substances to pass while
excluding
l di other.
th
• Passive Processes
– Without any energy input
• Active Processes
– ATP needed
Passive Processes
• Two types of passive processes;
Diffusion, Osmosis
2
Diffusion
• When the molecules or ions move from an area
off high
hi h concentration
i to area off low
l
concentration, down their concentration
gradient.
Diffusion
• Simple diffusion
– Non-polar and lipid soluble substances diffuse directly
thru the lipid bilayer.
– Oxygen, carbon dioxide, fat soluble, vitamins
• Facilitated diffusion
– Transported passively even though they are unable to
pass
– Glucose, other sugars, some amino acids, ions
3
Osmosis
• The diffusion of a solvent such as water thru a
selectively
l i l permeable
bl substance
b
– Occurs whenever the water concentration differs
on two sides of a membrane
http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf
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Osmosis
• Osmolarity
– The total concentration of all solute particles in a solution
• Hydrostatic Pressure
– Is the point in which the back pressure exerted by water
against the membrane cell is equal to
• Osmotic Pressure
– At this point, there is no further water entry
Tonicity
• The ability of a solution to change the shape or tone
off cells
ll by
b altering
lt i their
th i internal
i t
l water
t volume
l
• Isotonic: Concentration of both sides are same
• Hypotonic: Low concentration of solute
• Hypertonic: High concentration of solute
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Tonicity
• The ability of a solution to change the shape or tone
off cells
ll by
b altering
lt i their
th i internal
i t
l water
t volume
l
• Isotonic
• Hypotonic
• Hypertonic
Active Processes
• Two major means of active membrane
t
transport
t
– Active Transport, Vesicular Transport
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Active Transport
• Move solutes ions, sodium, calcium,
potassium,
t i
against
i t a concentration
t ti gradient
di t
with the help of ATP
• Primary
– Energy comes from hydrolysis of ATP
• Secondary
– Energy stored in ionic gradient
Primary Active Transport
• Sodium-Potassium pump
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Secondary Active Transport
• They move more than one substance at a time
– Symport systems
when the two substances move at a same time
– Antiport system
when the two substances move in opposites directions
Vesicular Transport
• Large particles are transported across cellular
membranes
b
via
i sacs calls
ll vesicles
i l
• Exocytosis
• Endocytosis
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Vesicular Transport
• Exocytosis
–S
Substances
bt
are ejected
j t d from
f
cell
ll into
i t the
th
extracelluar fluid
• Endocytosis
– Substances are move from the outside into inside
the cell
Endocytosis
• Phagocytosis
– Eating
E ti cells
ll
• Pinocytosis (Fluid-phases)
– Cell drinking
• Receptor-mediated
– External substance binds to membrane receptors
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Quiz Time!
1. What is the fluid derived from the blood that surrounds the outside
of the cell?
Interstitial Fluid
2 What is the difference between Endocytosis and Exocytosis?
2.
Endocytosis: Substances are move from the outside into inside
the cell
Exocytosis: Substances are ejected from cell into the
extracelluar fluid
3. What is osmotic pressure?
There is no further water entry
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4. What is the difference between Isotonic, Hypotonic, Hypertonic
solutions?
Isotonic: Concentration of both sides are same
Hypotonic: Low concentration of solute
Hypertonic: High concentration of solute
5. What are the 2 types of active processes?
Active Transport, Vesicular Transport
6 What
6.
Wh t is
i the
th difference
diff
between
b t
Symport
S
t andd Antiport?
A ti t?
Symport: When the two substances move at a same time
Antiport: When the two move in opposites directions
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