Transcript Section 2 cont.

Section 1 cont.
Turgor pressure- the
pressure that water
molecules exert against
the cell wall
Do the cells of this plant
have turgor pressure?

Plasymolysis- when a plant doesn’t receive
enough water and the cell membrane
shrinks from the cell wall; turgor pressure
is not maintained
Facilitated Diffusion

A type of passive transport that is used for
1) molecules too large to pass through
the cell membrane
2) molecules that do not dissolve in lipids
Facilitated diffusion uses a carrier protein.
What might this
molecule be?
Facilitated
Diffusion
1.
2.
3.
4.
Molecule
attaches to
protein.
Protein
changes
shape.
Molecule is
released to
other side.
Protein
returns to
original
shape.
Ion Channels

Membrane proteins move Na+, K+, Ca+2,
Cl- across the cell membrane
Three kinds of stimuli determine
whether “gates” are open:



1) stretching of the cell membrane
2) electrical signals
3) chemical signals
Section 2: Active Transport
-requires energy
-moves materials
up the
concentration
gradient (from
low to high
concentration)
The Sodium-Potassium Pump

Moves 3 sodium (Na) out and 2 potassium
(K) in…
Since there’s already more
sodium on the outside, energy
is required…
It’s like bailing
water out of a
boat that
continues to fill
The sodiumpotassium pump
moves 3 positive ions
Hmmm…
out for every 2
positive ions in;
which side of the cell
membrane is slightly
more negative than
the other??
The inside…


The inside of a cell (like a nerve cell) is
slightly more negative than the outside
This electrical gradient (difference in
charges) enables impulses to be sent
along nerve cells
Movement in Vesicles
Endocytosis
 Two types:
A. pinocytosis- a cell
takes in fluids or solutes
B. phagocytosis- a cell
takes in large particles or
whole cells
Exocytosis
 A process by which a
substance is released
from a cell
- toxins
-proteins
-waste products
Endocytosis
A color-enhanced transmission electron
micrograph of an amoeba engulfing green
algal cell for food.
An amoeba and endocytosis…
Many unicellular organisms feed by phagocytosis…
Phagocytes
-Your white
blood cells
ingest
bacteria
and viruses
Exocytosis