Transcript Cell Transport/Membrane

Cell Transport/Membrane
Cell Membranes
Functions:
a. Controls what enters and
exits the cell to maintain an
internal balance called
homeostasis
b.The “bouncer of the cell”, as
it is selectively
permeable
3. Structure of Membrane:
Phospholipid Bilayer
Phosphate head
Fatty acid tails
Hydrophilic = water loving
Hydrophobic = water fearing
Fluid Mosaic Model
Membrane
movement
animation
What do you think are things the cell needs?
-Water
-Sodium and calcium ions
-Nutrients
What do you think are things the cell doesn’t need?
-Harmful
ions
-Removes excess nutrients if the levels get too high
-Removes waste products
•Animations of Active
Transport & Passive
Transport
Types of Cellular Transport

Passive Transport
cell doesn’t use energy
1. Diffusion
2. Facilitated Diffusion
3. Osmosis

Weeee!!!
high
low
Active Transport
cell does use energy
1. Protein Pumps
2. Endocytosis
3. Exocytosis
This is
gonna be
hard
work!!
high
low
Passive Transport:
1.
Simple Diffusion
Animation
Diffusion: random movement of
particles from an area of high
concentration to an area of
low concentration until
equilibrium is reached
http://bio.winona.edu/berg/Free.htm
Diffusion in our capillaries…

Why does the CO2 leave the blood stream and O2 enter?...
Diffusion!
Rate of Diffusion
What do you think are the three factors that affect diffusion?
1. Concentration: The most important factor. The more the
concentrated the substances, the faster diffusion occurs.
2. Temperature: Increased
temperature can speed
diffusion because of
more rapid molecular
movement
3. Pressure: Increased
pressure will accelerate
molecular movement
and speed up diffusion.
Passive Transport:
2. Facilitated diffusion:
diffusion of specific particles
through transport proteins
found in the membrane
a. Allows certain molecules
to cross the membrane
b. Transports larger or
charged molecules
• Channel Proteins
animations
A
B
Facilitated
diffusion
(Protein
Channel)
Diffusion
(Lipid
Bilayer)
HIGH
LOW
Channel
Passive Transport:
3. Osmosis:
diffusion of water through
a selectively permeable membrane
Osmosis
animation
*Water will flow “down” the
concentration gradient to the side of
the membrane where the water
concentration is lower
•Water moves freely through
membrane while solutes can’t
Type of Solutions

Hypertonic: solution has a higher
concentration of solutes than inside the
cell.
Types of Solutions

Hypotonic: solution has a lower
concentration of solutes than inside the
cell.
Types of Solutions

Isotonic: cell environment has an equal
concentration of solutes as inside the cell
Red Blood Cells
Lysis
Plant Cells
What type of solution are these cells in?
A
B
C
Hypertonic
Isotonic
Hypotonic
Diffusion and Osmosis in the kidney

Maintaining water balance in the kidney can be inhibited
by a diuretic, a substance that causes the kidneys to allow
excess water loss. A very common diuretic is caffeine.
◦ Diuretics block the production of the hormone vasopressin,
an anti-diuretic hormone (ADH). When the blood has a
high concentration of sodium ions, the hypothalamus and
pituitary gland (both in the brain) triggers the release of
ADH which would tell the kidneys to reabsorb more water
to help rehydrate the body.
Basically, caffeine messes up the osmosis in your kidneys! It
makes you release more of the water you need to keep.
Therefore, your cells become dehydrated.
Digestion
Osmosis occurs in both the small and large intestines, with
the majority of osmosis occurring in the large intestine. As your
body processes food, it moves from the esophagus to the
stomach and then to the small intestine. While there, your body
absorbs important nutrients via osmosis. As food leaves the small
intestine, it travels to the large intestine, and some osmosis can
occur here as well.
The water “carries” the nutrients across the barrier.
Active Transport
Active Transport
 Protein
Pumps - transport of molecules/ions across
the membrane which requires energy.
Transported AGAINST the concentration gradient
 Example: H+ ion pump and Na+ K+ pump
Active Transport

Endocytosis: very large particles of material
are wrapped with plasma membrane and
moved into the cell in the form of vesicles.
Phagocytosis = “cell eating”
Pinocytosis = “cell drinking”
Active Transport

Exocytosis: reverse; quantities of material
are expelled from the cell without ever
passing through the membrane as
individual molecules
Endocytosis &
Exocytosis
 Hormone release, waste
animations