Download Movement Through the cell Membrane

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•The cell membrane regulates what enters and leaves
the cell and also provides the protection and support.
The cell takes in food and water and eliminates wastes through
the cell membrane.
Structure of the Cell Membrane: The
cell membrane is
actually a double layered sheet called the lipid
bilayer (remember lipid is another name for fat).
This bilayer forms a strong flexible structure that acts as a
barrier between the cell and its surroundings.
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• There
are two types of proteins associated with
the membrane integral and peripheral. Integral
membrane proteins are tightly bound to the membrane
and usually extend all the way through the membrane
(transmembrane proteins). These proteins act as
channels that allow certain substance to move from
the exterior to the interior of the cell. Peripheral
proteins are not totally embedded in the membrane. These
proteins can function as receptors.
Diffusion: Diffusion is a simple
process where molecules move
from a high concentration to a
low concentration.
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If a substance is small enough to move
through a cell membrane, then it will move
from a high concentration to a low
concentration until there are equal amounts
on both sides, this is called equilibrium.
Even after equilibrium is reached the molecules will continue to
move across the membrane. Roughly the same number of
molecule will move in each direction.
Solutions: In chemistry and
biology, a solution is a homogeneous
mixture composed of two or more
substances. In such a mixture, a
solute is dissolved in another
substance, known as a solvent. A
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Biology
common example is a solid, such as salt or sugar, dissolved in
water, a liquid.
There are three different ways to
classify a solution.
Hypotonic: contain a low concentration of
solute relative to another solution (e.g.
the cell's cytoplasm). When a cell is placed in a
hypotonic solution, the water diffuses into the cell, causing the
cell to swell and possibly explode.
Isotonic Solutions: contain the same
concentration of solute as an another
solution (e.g. the cell's cytoplasm). When a
cell is placed in an isotonic solution, the water diffuses into and
out of the cell at the same rate. The fluid that surrounds the
body cells is isotonic.
Hypertonic Solutions: contain a high
concentration of solute relative to
another solution (e.g. the cell's cytoplasm). When a
cell is placed in a hypertonic solution, the water diffuses out of
the cell, causing the cell to shrivel.
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Biology
Osmosis: Most biological membranes are selectively permeable;
this means that some substances can pass through it and others
. Osmosis is the diffusion of
water through a selectively
permeable membrane, this means
that water moves from a high
concentration to a low concentration
across a membrane.
can not
The inside of a cell is not just made of pure water it is a solution
that has many different things dissolved in it, such as sugar. If
there is a large amount of water on the outside of the cell in
which direction does the water want to go?
The water goes from an area of high concentration to an area of
low concentration until equilibrium is reached. There is no energy
required for diffusion to occur.
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Biology
Facilitated Diffusion: As we have seen some molecules are able
to pass directly through the cell membrane i.e. water. Other
molecules that are too big or have a charge are unable to diffuse
directly through the membrane, they need help.
This is where the embedded proteins come into play. The
membrane proteins act as channels that let molecules diffuse
from high to low concentrations, this is facilitated diffusion.
This process does not require energy.
Active Transport:
Active transport is a
process that requires
energy. This process
requires energy
because the protein
membranes are moving
things from low to high
concentration. Because
this action is pumping
against the gradient it
requires energy.
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Biology