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LESSON 2.pptx
1.
2. The plasma membrane, or the cell
membrane, provides protection for a
cell. It also provides a fixed
environment inside the cell. And that
membrane has a several different
function.
One of the great wonders of the cell
membranes is its ability to regulate the
concentration of substances inside the
cell.
What will happen if cell membrane
does not work properly?
3. The plasma membrane is composed of
phospholipids(fats) and proteins.
The phospholipids are arranged in a
double layer with a large protein
molecules dotted about in the membrane.
Some of the protein molecules form tiny
channels in the membrane.
4.
5. Substance need to pass through the
membrane to enter or leave the cell and
they do so in a number of ways. Some of
this process require no energy i.e they are
passive, while others require energy i.e
they active.
Passive transport is the movement of
substances across the membrane that
does not require the use of energy. In the
case of plasma membrane, only relatively
small, non polar materials can move
through the lipid bilayer.
Passive process include: Diffusion and
Osmosis
6. Diffusion causes small molecules that are
in a high concentration on one side of the
cell membrane to move across the
membrane until they are present in equal
concentrations on both sides.
7.
8. Let us discuss some examples of diffusion
in daily life.
Diffusion of perfume fragrance.
If you spray perfume or a room spray you
have witnessed the diffusion of the
fragrance in the entire room. Molecules in
the spray escape from the can (high
concentration) and spread evenly towards
the region with low concentration.
9. Diffusion of cream in coffee
When you add cream to a hot coffee, the
cream will diffuse throughout the cup of
coffee. Concentrated cream particles on
the top of coffee will condense near one
another.
10. In the animals body diffusion
is important for moving
oxygen and carbon dioxide
between the lungs and the
blood, for moving digested
food molecules from the gut
into the blood and for the
removal of waste products
from the cell.
11. Osmosis is the spontaneous net
movement of solvent molecules (usually
water) through a selectively permeable
membrane into a region of higher
concentration, in the direction that tends
to equalize the solute concentrations on
the two sides.
12.
13. What happens when red blood cells are placed in a
hypertonic solution?
When a red blood cell is placed in a
hypertonic solution, it shrinks as water is
drawn out of the cell and into
surrounding solution. If the same blood
cell is placed in a hypotonic solution, the
blood cell grows in size due to inflow of
water from the surrounding. Blood cells
in isotonic solutions do not shrink or
swell.
