movement in and out of the cell for o level and igcse students.pdf

this ppt is about the movement of molecules through the processes of diffusion, osmosis and active transport.

1. MOVEMENT IN AND OUT
OF THE CELL
Diffusion
Osmosis
Active Transport

2. DIFFUSION

3. DIFFUSION
•Diffusion is movement of molecules from a region of higher concentration to the region of lower concentration.
•Moleculesmoves down theconcentration gradientas a result of its randommovements.
Higher
Concentration Lower Concentration

5. DIFFUSION IN LIVING ORGANISMS
•Forliving cells, the principle of the movement down a concentration gradient is the same, but the cell is surrounded by
acell membranewhich canrestrict the free movement of the molecules
•The cell membrane is apartially permeable membrane-this means it allows some molecules to cross easily, but
others with difficulty or not at all
•The simplest sort of selection is based on the size of the molecules
•Diffusion helps living organisms to:
•obtain many of theirrequirements
•get rid of many of theirwaste products
•carry outgas exchange for respiration
•Plantsrequire oxygen for respiration at all times, as well ascarbon dioxide for photosynthesiswhen conditions
for photosynthesis are right (e.g. enough light and a suitable temperature)
•Co2 will diffuse into the alveolus;alveolus will diffuse out oxygen into the red blood cell; blood turns into oxygenated
blood

7. BROWNIAN MOTION
•All particles move randomly at all
times
•This is known as Brownian
motion
•The energy for diffusion comes
from the kinetic energy of this
random movement of molecules
and ions

8. FACTORS THAT INFLUENCE
DIFFUSION
•SURFACE AREA TO VOLUME RATIO:
•The bigger the cell or structure is, the smaller the
surface area to volume ratio.
•Slows down the rateat whichsubstancesmoves
across the surface.
•Cells adapted todiffusionalways have increased
surface area.

9. VILLI AND ROOT HAIR CELL

10. FACTORS THAT EFFECT DIFFUSION
•MEMBRANES
(DISTANCE)
•The smaller the distance
molecules have to cover, the
faster will be the rateof
diffusion.
•The walls of capillaries and
alveoli are one cell thick only to
ensure thefastest possible
transport ofgaseous exchange.

11. FACTORS THAT EFFECT DIFFUSION
•TEMPREATURE:
•The higher the temperature the
faster the molecules move as they
have more energy (Brownian
motion)
•The higher the temperature, the
more the collisions hence there
will be the faster rate of diffusion
across the membrane.

12. FACTORS THAT EFFECT DIFFUSION
•CONCENTRATION
GRADIENT:
•The more the concentration
difference in either side of the
membrane the faster the movement
across the membrane will occur.
•This is because theside of the
membrane with higher
concentrationwill have more number
of random collisionsagainst the
membrane, hence more diffusion.

13. QUESTIONS
•Q1)Define diffusion as the movement of molecules from a region of their
higher concentration to a region of their lower concentration, down a
concentration gradient
•Diffusion: Movement of molecules of a substance down the
concentration gradient. No energy required Can occur in liquids and
gases. Can be through or not through a partially permeable membrane
When a concentration gradient exists, diffusion will contnue until the
particles are evenly distributed throughout the region

14. OSMOSIS

15. OSMOSIS
•All cells are surrounded by a partially
permeable membrane
•Water moves in and out of the cells
through osmosis.
•Osmosis is the netmovementof water
molecules from a region of high water
potentialto a region of low water potential,
down theconcentration gradient.
•Cell membrane is partially permeable
membrane, so it allows only small
molecules (water) to pass through as
compared to largesolute molecules.

16. OSMOSIS
•High water potential region is a dilute
solution
•Low water potential region is a
concentrated solution.
•The right waytoexplainthe process of
osmosis is the use of termwater
potentialsince we are talking about
thewatermoleculesand
thetermconcentration is used when
talking about the solute molecules.

17. THE TONICITY
•The HypotonicSolutions: hashigh water potential and low
concentrationofsolutes.
•The Hypertonic Solutions: has low water potential and high concentration
ofsolutes.
•The IsotonicSolutions: has equal water potential and
equalsoluteconcentration in both thesolutions.

18. SOLUTION WITH HIGH WATER POTENTIAL
(HYPOTONIC SOLUTION)
PLANT CELL
•Cell sap has low water potential than the
solution outside the cell.
•Vacuoleincreases in size; pushes the cell
contents against the cell wall.
•Strong elastic cell
wall;preventsoverexpansionofcellby
exertingand opposingpressure as water
enters the cell.
•Whenplant cell expands it swollen or
turgid. Cell doesn't burstas it is
protectedby cell wall. This turgidity of cell
is called turgor. The pressure exerted by
water on the cell is calledturgor pressure
ANIMAL CELL
•Animal cell has low water potential as
compared to the solution outside the cell.
•The cellkeeps on expanding and swelling
as the water enters through partially
permeablemembrane.
•Animal cell have no cell wall, hence,
thecellisnot protected and bursts.
•This is because of the osmoticimbalance
in the cell, hencethe process, cytolysis or
osmotic lysis.

19. Cytolysis/ Osmotic Lysis of
Red Blood Cell
CYTO: Cell
LYSIS: breakage or rupture of cell
wall or cell membrane

20. SOLUTION WITH LOW WATER POTENTIAL
(HYPERTONIC SOLUTION)
PLANT CELL
•Cell sap has high water potential as
compared to the water potential of the
solution.
•Water leaves thecellthrough osmosis.
Cell loseswater; vacuoledecreases in
size; cytoplasm shrinksaway from the
cell wall.
•The shrinking away of the cytoplasm
from the cell wall is known as
plasmolysis of cell. The cell is said to
be plasmolyzed.
ANIMAL CELL
•Cytoplasm has high water potential as
compared to the water potential of the
solution.
•Water leaves the cell through osmosis.
•The animal cellshrinks and little spikes
appear on the cell membrane. The cell
is said to be crenated.
•Red blood cells is one example of
animal cell which undergo crenation.

21. THE PROCESS OF CRENATION
•Cells are usually in an isotonic solution inside the body meaning there is same concentration level
of solute and water, in and out of the cell.
•The equilibrium allows the cells to maintain their shapes, with water moving in and out of the
cellat a constant rateand maintainingsame osmotic pressure throughout across the
semipermeable membrane.
•When the equilibrium is disrupted by the higherconcentration of solute in the solution, it creates
hypertonicenvironmentwhich causes the intracellular water dodiffuse out throughosmosis.
•The cellsstart to shrivel and dry upand form abnormal spikesand notches on the cell
membrane.
•This process is called crenation.

22. SOLUTION WITH EQUAL WATER POTENTIAL
(ISOTONIC SOLUTION)
•Cells immersed in a solution with same
water potential does not change their
shape or size, neither do they undergo
crenation nor do they have to experience
cytolysis/osmotic lysis.
•This is because the cellhave same water
potential as thesolutionoutside the
cell,so is the concentration level ofthe
soluteand the cell.

23. EXPERIMENTS OF OSMOSIS
EXPERIMENT 1
•AIM: TO SHOW OSMOSIS
•APPARATUS: Beaker;Retord stand; Thistle funnel;
Water;Sucrose solution; Cellophane paper
•PROCEDURE:
•Tie a piece od cellophane paper tightly over the mouth of
thistle funnel. Fill the funnel with 5% sucrose solution and
mark the level of the solution.
•Lower the funnel into the beaker ofwater such that the
liquid levelsinside and outside the funnel are same.
•Set up the second experiment the same waybut with
distilled waterinside the funnel instead of sucrose solution.
•Observe and note the level ofthe solution inside
eachfunnel
•OBSERVATIONS:
•EXPERIMENT A) Water potential was high in
the beaker and water potential was low in the
thistle funnel, so, water move from the beaker to
the thistle funnel by the process of osmosis and
the level of the concentration in the thistle funnel
increases.
•EXPERIMENT B)Water potential was high
inthe thistle funnel and water potential was low in
thebeaker, so, water move from the thistle funnel
tothe beaker by the process of osmosis andthe
level of the concentration in the thistle
funneldecreases.

24. Oxygenated blood
•High concentration of oxygen
•Alveoli diffuse out oxygen into the
red blood cells
Deoxygenated blood
•High concentration of
carbondioxide
•Red blood cells diffuse out
carbondioxide into the alveoli