Download 8_SEMIPERMEABLEMemb

FL #8 Cell Membranes and
Semipermeability
Cell Biology Standard 1A
Know that cells are enclosed
within semipermeable
membranes that regulate what
enter and leave the cell.
October 22-23, 2003
Tony Gonzales
(Cell Biology 1A) The function of
the cell membrane?
A. Breaks down lipids, carbohydrates, and proteins
from food.
B. Stores water, salts, proteins, and carbohydrates.
C. Keeps the cell wall in place.
D. Regulates which materials enter
and leave the cell.
Cellular Components
1. Plasma (cell) membrane
Each eukaryotic cell has a cytoplasmic matrix
containing specialized membrane-bound components
called organelles. The cell or plasma membrane is a
lipid bilayer containing proteins, cholesterol, and
functions to
regulate what goes in and out of
the cell. The plasma membrane, by limiting the
oligosaccharides that
transport of some things and facilitating the movement
of others helps to maintain the internal environment of
the cell,
The following slides show
the different means by
which materials move in
and out of the cell and
other semi-permeable
membrane.
The cartoon to the right illustrates passive
diffusion. Diffusion is when material
moves from high to low
concentration.The dashed line is intended
to indicate a membrane that is permeable to
the molecules or ions illustrated as red dots.
Initially all of the red dots are within the
membrane. As time passes, there is net
diffusion of the red dots out of the
membrane, following their concentration
gradient. When the concentration of red dots
is the same inside and outside of the
membrane the net diffusion ceases. However,
the red dots still diffuse into and out of the
membrane, but the rates of the inward and
outward diffusion are the same resulting in a
net diffusion of O.
Shown to the right is an
animation which illustrates
protein mediated,
facilitated diffusion out
of a cell.
Facilitated diffusion=
Is when proteins act as
channels to facilitate the
movement of material in or
out of the cell.
Facilitated Diffusion
Shown to the right is an animation illustrating how secretion vesicles approach the
plasma membrane, fuse with the plasma membrane and dump their soluble
contents outside of the cell. This process is called exocytosis and it is mechanism by
which cells can secrete molecules like proteins. For example, the epithelial cells in
the breast use secretion vesicles to put the major protein of milk (casein) outside of
the cell which synthesized it.
Active Transport-When materials move
across a cell membrane against a
concentration difference. When materials
move from an area of low concentration
to an area of high concentration.
1. (Cell Biology 1A) An animal cell
that is surrounded by fresh
water will burst because the
osmotic pressure causes?
A. Water to move into the cell through the cell membrane.
B. Water to move out of the cell through the cell membrane.
C. Solutes to move into the cell through the cell membrane.
D. Solutes to move out of the cell through the cell membrane.
Cell
Osmosis- is when water move
from high to low concentration
across a membrane.
2. (Cell Biology 1A) Which of the
following is a function of the cell
membrane?
A. Breaks down lipids, carbohydrates, and proteins
from food.
B. Stores water, salts, proteins, and carbohydrates.
C. Keeps the cell wall in place.
D. Regulates which materials enter
and leave the cell.
Cellular Components
1. Plasma (cell) membrane
Each eukaryotic cell has a cytoplasmic matrix
containing specialized membrane-bound components
called organelles. The cell or plasma membrane is a
lipid bilayer containing proteins, cholesterol, and
functions to
regulate what goes in and out of
the cell. The plasma membrane, by limiting the
oligosaccharides that
transport of some things and facilitating the movement
of others helps to maintain the internal environment of
the cell,
3. (Cell Biology 1A) During
diffusion materials move?
A. From high to low concentration.
B. From low to high concentration.
C. Across the membrane with the assistance of a protein.
D. Across the membrane with the assistance of a lipid.
4. (Cell Biology 1A) Active
transport moves materials?
A. From high to low concentration.
B. From low to high concentration.
C. Across the membrane with the assistance of a protein.
D. Across the membrane with the assistance of a lipid.
5. (Cell Biology 1A) Facilitated
diffusion is when materials
move?
A. From high to low concentration.
B. From low to high concentration.
C. Across the membrane with the assistance of a protein.
D. Across the membrane with the assistance of a lipid.