Plasma MEMBRANE structure and function.ppt

For science subjecf specifically cell and molecular biology

1. PLASMA MEMBRANEPLASMA MEMBRANE

2. Plasma Membrane
•Boundary that separates the living cellliving cell from
it’s non-livingnon-living surroundings.
•Phospholipid bilayerPhospholipid bilayer
•AmphipathicAmphipathic - having both:
hydrophilic heads
hydrophobic tails
•~8 nm thick
PhospholipidPhospholipid

3. Plasma Membrane - cont.Plasma Membrane - cont.
•Controls trafficControls traffic into and out of the cell with
phospholipidsphospholipids and and transport proteinstransport proteins..
•Selectively permeableSelectively permeable
Transport proteinTransport protein

4. Selective PermeabilitySelective Permeability
•The propertyproperty of biological membranesbiological membranes
which allows some substances to cross more
easily than others.

5. Fluid MosaicFluid Mosaic
•1972 - SingerSinger and NicolsonNicolson called the
membrane a “Fluid Mosaic Model”.
•Mosaic:Mosaic:different proteins embedded in
the phospholipids.
•Fluid:Fluid:proteins and phospholipids can
move freely in the
membrane.

6. Fluid Mosaic - cont.Fluid Mosaic - cont.
•Components of a phospholipid bilayer.
1.1.phospholipidsphospholipids
2.2.proteins - proteins - enzymes, receptors, enzymes, receptors,
transport.transport.
3.3.glycolipidsglycolipids
4.4.glycoproteinsglycoproteins
5.5.carbohydratescarbohydrates
6.6.cholesterolcholesterol

7. Transport ProteinsTransport Proteins
•TransportsTransports moleculesmolecules or ionsions across
biological membranes
•3 types of transport proteins3 types of transport proteins:
11.uniportuniport
22.symportsymport
33.antiportantiport

8. Uniport Transport ProteinUniport Transport Protein
•Carries a single solutesingle solute across the membrane.
extracellular
fluid
intracellular
fluid

9. Symport Transport ProteinSymport Transport Protein
•Translocate 2 different solutesTranslocate 2 different solutes simultaneously
in same direction.
intracellular
fluid
extracellular
fluid

10. Antiport Transport ProteinAntiport Transport Protein
•Exchanges 2 solutesExchanges 2 solutes by transporting them in
opposite directionsopposite directions.
intracellular
fluid
extracellular
fluid

11. DiffusionDiffusion
•The net movement of a substance (molecules)
down a concentrationconcentration gradientgradient from an area of
highhigh concentrationconcentration to an area of lowlow
concentrationconcentration.
•passive transport:passive transport:NONO energyenergy is expended.
•facilitated diffusion: facilitated diffusion: type of passive transportpassive transport
which uses transport proteins.transport proteins.

12. OsmosisOsmosis
•The movement of waterwater across selectively selectively
permeable membranespermeable membranes.
•The waterwater moves from a high concentrationhigh concentration
to low concentrationlow concentration.

13. Question:Question:
What’s in a Solution?What’s in a Solution?
Answer:Answer:
•solutesolute+solventsolventsolutionsolution
•NaClNaCl +HH
2200 saltwatersaltwater

14. HypertonicHypertonic
•A solutionsolution with a greater solutegreater solute
concentrationconcentration compared to another solutionsolution.
3% NaCl
97% H
2O
Red Blood Cell
5% NaCl
95% H
2
O
solutionsolution

15. HypotonicHypotonic
•A solutionsolution with a lower solute concentrationlower solute concentration
compared to another solutionsolution.
3% Na
97% H
2O
Red Blood Cell
1% Na
99% H
2
O
solutionsolution

16. IsotonicIsotonic
•A solutionsolution with an equal solute concentrationequal solute concentration
compared to another solutionsolution.
3% Na
97% H
2
O
Red Blood Cell
3% Na
97% H
2
O
solutionsolution

17. Movement of HMovement of H
22OO
•Water will “ALWAYS”“ALWAYS” diffuses down a
concentration gradient from a HYPOTONICHYPOTONIC
solutionsolution to a HYPERTONICHYPERTONIC solutionsolution.
““ALWAYS REMEMBER”ALWAYS REMEMBER”
•HYPOTONICHYPOTONIC  HYPERTONICHYPERTONIC

18. Animal CellsAnimal Cells
•Animal cellsAnimal cells placed into a hypotonic solution
will HEMOLYSIS (EXPLODE).HEMOLYSIS (EXPLODE).
•Animal cellsAnimal cells placed into a hypertonic solutionhypertonic solution
will CRENATE (SHRIVEL).CRENATE (SHRIVEL).
Hemolysis
Crenation
RedRed
BloodBlood
CellsCells

19. Plant CellsPlant Cells
•Firmness or tension (vacuole full)(vacuole full) that is found
in plant cells (cell wall) that are in a hypotonic
environment is called TURGIDTURGID..
•This process is called TURGOR PRESSURE.TURGOR PRESSURE.
Water
Water
Cell
Wall
Water
Central
Vacuole

20. Plant CellsPlant Cells
•When the plasma membraneplasma membrane pulls away from
the cell wallcell wall (vacuole empty)(vacuole empty) in a hypertonic hypertonic
environmentenvironment (loss of water)(loss of water) is called
PLASMOLYSIS.
Water
Water
Cell
Wall
Water
plasma membraneplasma membrane

21. Active TransportActive Transport
•The movement of moleculesmovement of molecules (small or large)
across the plasma membraneplasma membrane in which energy energy
(ATP)(ATP) is requiredrequired.
•Examples:Examples:
1.1. Sodium (Na) - Potassium (K) PumpSodium (Na) - Potassium (K) Pump
2.2. ExocytosisExocytosis
3.3. EndocytosisEndocytosis

22. Sodium-Potassium Pump
•The mechanism that uses energy (active transport)energy (active transport)
released from splitting ATPsplitting ATP to transport Sodium Sodium
(Na(Na
++
)) out out of and Potassium (KPotassium (K
++
) into cells. ) into cells.
extracellular
fluid
intracellular
fluid
Na
+
Na
+
K
+ K
+

23. Question:Question:
•How are large molecules transported into How are large molecules transported into
and out of the plasma membranes?and out of the plasma membranes?

24. Answer:Answer:
•Exocytosis and EndocytosisExocytosis and Endocytosis

25. ExocytosisExocytosis
•Cell Cell secretes macromoleculessecretes macromolecules (proteins and (proteins and
other biochemicals) other biochemicals) outout of cell. of cell.
•Part of the Endomembrane System:Part of the Endomembrane System: the
fusion of transport vesicles with plasma
membrane.

26. EndocytosisEndocytosis
•The energyenergy requiring movementmovement of particlesparticles
(foreign or natural)(foreign or natural) intointo the cell.
•3 types of endocytosis:3 types of endocytosis:
A.A.PhagocytosisPhagocytosis
B.B.PinocytosisPinocytosis
C.C.Receptor-mediated endocytosisReceptor-mediated endocytosis

27. A. A. Phagocytosis
•Cell eating:Cell eating: cells engulf particles with
pseudopodiapseudopodia and pinches off a food pinches off a food
vacuolevacuole..
•Two examples:Two examples:
1.1.White Blood CellWhite Blood Cell
2.2.AmoebaAmoeba
FoodFood
VacuoleVacuole White Blood Cell
Bacteria

28. B. PinocytosisB. Pinocytosis
•Cell drinking: droplets of extracellular fluid
are absorbedabsorbed intointo the cell by small vesiclessmall vesicles.
•Example:Example:
1.1.FungiFungi
Food Particles
Hyphae

29. C. Receptor-Mediated EndocytosisC. Receptor-Mediated Endocytosis
•Importing specific macromolecules (hormones) specific macromolecules (hormones)
intointo the cell by the inward budding of vesiclesinward budding of vesicles
formed from coated pits (receptors).
Hormones
Receptors
Liver Cell