Transcript The Plasma Membrane - Lamar County School District

I. The Plasma Membrane
Quiz:
Cell Membrane
1. Controls what comes in and out of the cell. It
is selectively permeable.
2. Protects and separates the cell from
its environment
3. It is often called a fluid mosaic
model
b. Made of a phospholipid bilayer
• i. Two layers of phospholipids
• ii. Arranged tail to tail
ii.
Has various proteins, carbohydrates
and cholesterol mixed in
Figure 6-1
Simple Plasma Membrane
• proteins are imbedded in the plasma
membrane like raisins in raisin bread
II. Passive Transport- the
movement of particles in and
out of the cell without using the
cell’s energy.
• A. Diffusion - movement of particle- like gases
across the cell membrane.
• B. Makes use of a concentration gradient- the
SOLUTE always moves from HIGH
concentration to low concentration.
Will continue until dynamic equilibrium
is reached

•Can make use of transport proteins- which are
selective for certain particles.
Diffusion of Oxygen
C. Facilitated Diffusion
• c. Facilitated diffusion- process of moving
particles across the cell membrane using
transport proteins.
– i. Transport proteins-found in the cell membrane
• 1. Allow some types of ions, sugars and amino acids to
pass through the cell membrane
• 2. There are different types -each is selective - specific
for certain particles
– ii. Move particles from areas of HIGH concentration to
areas of LOW concentration-moves down the concentration
gradient
– iii. Form of passive transport ---no energy
Facilitated diffusion Fig. 6-3
d. Osmosis-type of passive diffusion -it does not
use the cell’s energy
 1. It is always the
movement of WATER
particles
 2. It moves WATER
molecules across a
selectively
permeable
membrane through
which the solute
(dissolved particles)
cannot pass
• ii. Makes use of a concentration gradient always moves from HIGH concentration to
low concentration
• Iii. Will continue until dynamic equilibrium of
the solute is reached.
Osmosis the movement of water
Osmosis can create 3 types of solutions:
•
3. Hypotonic solution
1. Isotonic Solution
2. Hypertonic Solution
• 1. Isotonic solution -the solution on the
outside of the plasma membrane has the
same concentration as the solution on the
inside of the membrane.
– a. There is no NET movement of WATER
molecules
– b. Water will move in and out of the cell at the
same rate
– c. The cell will remain the same size
– d. Animal cells do best in isotonic solution
Isotonic Solution
2. Hypertonic solutions--the solution outside
the cell has less water and more solute than the
solution inside the cell.
http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm
• a. Water rushes out of the cell
• b. Cell shrivels up
• c. Causes plasmolysis in plants, plants wilt
Ex: slugs
• 3. Hypotonic solution - the solution on
the inside of the cell membrane has less
water and more solute than the solution
outside of the cell.
http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm
• a. Water rushes into the cell
• b. Cell swells like a big
O
c. Plant cells become turgid due to water pressing outward
against cell wall---creates turgor pressure
d. Plant cells do best in a hypotonic solution.
• e. Animal cells swell & burst (lyse) if they take in too much
water
III. Active Transport- transport proteins,
endocytosis and exocytois
• A. Moves molecules in and out of the cell
– Moves materials AGAINST the concentration
gradient
– Requires the cell’s energy-- $$$$$$
• iii. Uses transport proteins to help move
materials in and out of the cell—3 types
include:
1. Carrier Proteins
2. GATE Proteins
3. Channel Proteins-like a straw things can
pass through
b. Endocytosis-the process of taking in
large particles
i. surrounds the particles with the cell membrane
ii. Requires cell energy --$$$$$
iii. “en” - means “ enter”
2 types of endocytosis
• 1. Phagocytosis- process of engulfing solid
particles to create vesicles
• 2. Pinocytosis- the process of engulfing liquid
particles
c. Exocytosis - process of removing
large particles
i. Used to get rid of wastes, undigested food or to
release hormones
ii. In the cell the material is enclosed in a vesicle,
vesicle fuses with the cell membrane and the
material is released outside of the cell
iii. “ex” - means “exit”
• 1. Look at the diagram below. The
animal cell has a concentration of
0.7% inside the cell membrane and it
is placed in a salt solution with a
concentration of 18.5 %. What will
happen if the cell remains in the
solution? Explain your answer in
terms of osmosis.
18. 5%
0.7%
• 2. A red blood cell contains a 0.9%
concentration of salt inside the cell.
If the red blood cell is placed in a
solution that is pure water, what will
happen to the cell? Is the solution
hypertonic, hypotonic, or isotonic?
• 3. A plant cell contains a 1%
concentration of solute inside the
cell. If the plant cell is placed in a
solution that is 5% solute, what will
happen to the cell? It the solution
hypertonic, hypotonic or isotonic?
• Saturated fats
Unsaturated fats