Transcript cell transport notes

Cell Transport





Osmosis
Diffusion
Isotonic, Hypotonic, Hypertonic
Facilitated Diffusion
Active Transport
The Cell Membrane



Maintains homeostasis for the cell by
allowing waste and other products to
leave the cell.
Selectively Permeable – allows only
some materials in and out of the cell.
Water and oxygen move freely across
the cell's membrane.
Structure of Cell Membrane

Has a phospholipid bilayer (2 layers of
fat).

The phospholipids have a:
– hydrophilic head (water loving)
– two hydrophobic tails (water fearing)
Cell Membrane

The Cell Membrane is also called
“The Fluid Mosaic Model”
– Because the membrane is flexible and the
lipids move within the membrane. (like
water molecules move in the currents of
a lake).
– Also because proteins create a “mosaic”
or pattern on the surface of the
membrane.
Passive Transport


No energy is required for the
molecules to move into or out of the
cell.
Three Types:
– Diffusion
– Osmosis
– Facilitated Diffusion
Diffusion



DIFFUSION - MOLECULES move from
areas of high concentration to areas of
low concentration.
EQUILIBRIUM- when the molecules
are even throughout a space.
Concentration gradient - a difference
between concentrations in a space.
Osmosis



OSMOSIS - the movement of water across
the cell membrane from high concentration
to low concentration.
A simple rule to remember is:
Salt is a solute. When it is concentrated
inside or outside the cell, it will draw the
water in its direction. This is also why you
get thirsty after eating something salty.
Three Types of Solutions
 Isotonic
 Hypotonic
 Hypertonic
Isotonic Solution“ISO” means same

If the concentration of solute (salt)
is equal on both sides, the water
will move back and forth equally.
Hypotonic Solution“HYPO” means less


There are less solute (salt) molecules outside the
cell (since salt sucks) water will move into the cell.
The cell will gain water and grow larger.
In plant cells, the central vacuoles
will fill and the plant becomes stiff
and rigid, the cell wall keeps the
plant from bursting.
In animal cells, the cell may
be in danger of bursting,
organelles called CONTRACTILE
VACUOLES
will pump water out of the cell to prevent this.
Hypertonic Solution“Hyper” means more
There are more solute (salt) molecules
outside the cell, so the water is sucked
out of the cell.
 The cells shrink,
causes cell to die.

Can Drinking Salt Water
Hurt You?



Yes! This is why it is dangerous to drink sea
water.
Its a myth that drinking sea water will cause
you to go insane, but people marooned at
sea will speed up dehydration (and death)
by drinking sea water.
This is also why "salting fields" was a
common tactic during war. It would kill the
crops in the field, thus causing food
shortages.
Facilitated Diffusion


Movement of large molecules across
the cell membrane using PROTEINS!!
Molecules move from high to low
concentration (no energy required) but
are "helped" by carrier proteins.
Active Transport- REQUIRES
ENERGY b/c materials are moving against
the concentration gradient!

Active Transport – moving
molecules from an area of LOW
concentration to a HIGH
concentration.
Types of Active Transport

Endocytosis- moving large particles
INTO the cell by the cell membrane
engulfing them.
– Phagocytosis: engulf large food particles
– Pinocytosis: engulf large fluid particles

Exocytosis – moving large particles
OUT of the cell.