1. The net movement of particles from an
area of high concentration to an area of
low concentration
Due to the random movement of particles
A passive process which means that no
energy is needed
3. Dissolved substances have to pass through
the par tially permeable cell membrane
to get into or out of a cell.
Diffusion is one of the processes that allows
this to happen..
What substances are
we talking about?
4. All living cells rely on diffusion to live.
They use it for:
Getting raw materials for
respiration (dissolved
substances and gases)
Removing waste products (eg. from respiration)
Plants use of photosynthesis (raw materials
in, waste products out)
Examples…
5. Oxygen in inhaled air diffuses
through the lungs and into the
bloodstream. The oxygen is
then transported throughout
the body.
Carbon dioxide is the waste gas
produced
by
respiration.
Carbon dioxide diffuses from
body
tissues
into
the
bloodstream and is exhaled via
the lungs.
6. Movement of glucose from small intestine lumen into blood
capillaried of villi
capillary network
Villi
small intestine
blood vessels
The villi and microvilli result in a LARGE SURFACE AREA, for maximum absorption.
7. A synapse is a junction between two neurones across
which electrical signals must pass.
Neurotransmitter molecules diffuse from vesicles towards
the neurotransmitter receptors, moving from an area of high
concentration to low concentration.
8. •The placenta is an organ
that develops in the uterus
during pregnancy.
•The umbilical cord connects
the placenta to the foetus.
•It enables nutrients and oxygen to
pass from the mother to the foetus by
diffusion, and waste substances to
diffuse from the foetus back to the
mother.
9. •The placenta can stop
certain molecules and
bacteria from diffusing through
•It is unable to stop many
harmful substances such as
alcohol, chemicals and some
types of virus from diffusing
through, reaching the foetus.
10. How does the placenta work?
umbilica
l
cord
umbilica
l
artery
umbilical
vein
11. carbon dioxide + water → oxygen + glucose
Carbon dioxide diffuses
in through the stomata
Oxygen and water diffuse
out of the stomata
During photosynthesis, the
level of CO2 is low inside the
leaf
This creates a big
concentration gradient so CO2
12. movement of water molecules across a selectively
permeable membrane from a region of higher water
concentration to a region of lower water concentration.
movement of water molecules across a selectively
permeable membrane from a region of lesser solute
concentration to a region of higher solute
concentration.
a specialized case of diffusion in which the
microscopic holes of membranes were so small that
they allow the passage of water molecules but not the
sugar molecules.
13. If the area outside the cell has more salt
– then water will be sucked out of the
cell
18. Cell may burst, or
organelles called
“contractile vacuoles”
remove excess water
19. Cell will shrink or die,
plants wilt
Why is it dangerous
to drink sea water?
Why does pouring
salt on a slug kill it?
20. h
res
w
ter
a
There is low concentration of
There is low concentration of
F
solutes in extracellular fluids
solutes in extracellular fluids
than in cells. As a reault, water
than in cells. As a reault, water
Hypotonic –"HYPO" means less, less solute, Dilute,
tend to move first inside cell
tend to move first inside cell
higher water potential
and then inside vacuole. When
and then inside vacuole. When
Hypertonic – "HYPER" means more,more solute,
vacuole increases in size,
vacuole increases in size,
cytoplasm presses against the
concentrated, low water potential cytoplasm presses against the
interior of cell wall, which
interior of cell wall,
Isotonic - "ISO" means the same when both solutions which
expand a little. Due to strong
expand a little. Due to strong
have the same water potential (‘iso’: sameplant cell does not
as;
cell wall plant cell does not
cell wall
‘tonicity’: strength of solution).
repture but instead become
repture but instead become
This is why it is dangerous to drink
rigid or turgid.
rigid or turgid.
sea most- plant cell live in_________environment.
water its a myth that drinking
sea water will cause you to go
insane, but people marooned at
sea will speed up dehydration (and
sea water
death) by drinking sea water.
/ocean
This is also why "salting fields" was
a common tactic during war, it
would kill the crops in the field,
thus causing food shortages.
21.
Hypotonic Solutions : contain a low concentration of solute relative to
another solution (e.g. the cell's cytoplasm). When a cell is placed in
ahypotonic solution, the water diffuses into the cell, causing the cell to swell
and
possibly
explode.
Hyper tonic 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.
Isotonic Solutions : contain the same concentration of solute as an
another solution (e.g. the cell's cytoplasm). When a cell is placed in
anisotonic solution, the water diffuses into and out of the cell at the same
rate. The fluid that surrounds the body cells is isotonic.
22. Water enter plant
(root) cells by______,
because in the rootswater
the
The solution in the roots
The solution
of potential hypertonic,
soil is
of the plants is hypertonic,
the plants is of
drawing in water from the
drawing in water from the
usually higher
surrounding hypotonic soil. than
surrounding hypotonic soil.
Roots are designed as
Roots are designed as
the water potential of
selectively permeable
selectively permeable
a plant‘s cell sap.
membranes, admitting not
membranes, admitting not
only water, but some
only water, but some
useful solutes.
useful solutes.
23.
Xylem tissue: Water and ions
travel upwards
Phloem tissue: Sucrose and
other assimilates travel upwards
and downwards
Movement of water in the xylem
and phloem is by mass flow.
Everything travels in the same
direction within each of column of
xylem or phloem
Note that neither plant transport
system carries O2 or CO2
Xylem tissue
vessel element
tracheids
Start as living cells
(nucleus, cell wall)
Then differentiated into
specialised structures
and died
No living material
Just empty shells
24.
sometimes fatal medical condition known as water intoxication
occurs when people drink a large amount of water very rapidly,
causing a dilution of the water which flows freely through their
bodies. This diluted solution is capable of pushing through the
cell membranes, thanks to osmosis, and it can cause cells to
explode as they expand to accommodate the water.
Conversely, when people become dehydrated, cells shrivel and
dehydrated
die as the free-flowing water in the body becomes highly
concentrated with solutes, causing water to flow out of the cells
in an attempt to reach an isotonic state.
25.
A 5% urea solution is hypotonic to a 10% urea
solution.
yes
no
26. Reverse
osmosis
is
a
separation process that uses
pressure to force a solvent
through a membrane that
retains the solute on one side
and allows the pure solvent to
pass to the other side,
meaning it allows the passage
of solvent but not of solute. In
reverse osmosis, the idea is
to use the membrane to act
like an extremely fine filter to
create drinkable water from
salty water.
The membranes used
for reverse osmosis
have a dense barrier
layer in the polymer
matrix
where
most
separation occurs.
