1. PLASMA MEMBRANE

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

3. Plasma Membrane - cont.
• Controls traffic into and out of the cell with
phospholipids and transport proteins.
• Selectively permeable
Transport protein

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

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

6. Fluid Mosaic - cont.
• Components of a phospholipid bilayer.
1. phospholipids
2. proteins - enzymes, receptors, transport.
3. glycolipids
4. glycoproteins
5. carbohydrates
6. cholesterol

7. Transport Proteins
• Transports molecules or ions across
biological membranes
• 3 types of transport proteins:
proteins
1. uniport
2. symport
3. antiport

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

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

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

11. Diffusion
• The net movement of a substance (molecules)
down a concentration gradient from an area of
high concentration to an area of low
concentration.
concentration
• passive transport: NO energy is expended.
• facilitated diffusion: type of passive transport
which uses transport proteins.

12. Osmosis
• The movement of water across selectively
permeable membranes.
membranes
• The water moves from a high concentration
to low concentration.
concentration

13. Question:
What’s in a Solution?
Answer:
• solute + solvent → solution
• NaCl + H20 → saltwater

14. Hypertonic
• A solution with a greater solute
concentration compared to another solution.
solution
3% NaCl solution
97% H2O 5% NaCl
95% H2O
Red Blood Cell

15. Hypotonic
• A solution with a lower solute concentration
compared to another solution.
solution
3% Na solution
97% H2O
1% Na
99% H2O
Red Blood Cell

16. Isotonic
• A solution with an equal solute concentration
compared to another solution.
solution
3% Na solution
97% H2O 3% Na
97% H2O
Red Blood Cell

17. Movement of H2O
• Water will “ALWAYS” diffuses down a
concentration gradient from a HYPOTONIC
solution to a HYPERTONIC solution.
solution
“ALWAYS REMEMBER”
• HYPOTONIC → HYPERTONIC

18. Animal Cells
• Animal cells placed into a hypotonic solution
will HEMOLYSIS (EXPLODE).
• Animal cells placed into a hypertonic solution
will CRENATE (SHRIVEL).
Hemolysis
Crenation
Red
Blood
Cells

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

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

21. Active Transport
• The movement of molecules (small or large)
across the plasma membrane in which energy
(ATP) is required.
required
• Examples:
1. Sodium (Na) - Potassium (K) Pump
2. Exocytosis
3. Endocytosis

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

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

24. Answer:
• Exocytosis and Endocytosis

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

26. Endocytosis
• The energy requiring movement of particles
(foreign or natural) into the cell.
• 3 types of endocytosis:
A. Phagocytosis
B. Pinocytosis
C. Receptor-mediated endocytosis

27. A. Phagocytosis
• Cell eating: cells engulf particles with
pseudopodia and pinches off a food
vacuole. Bacteria
• Two examples:
1. White Blood Cell
2. Amoeba
Food
Vacuole White Blood Cell

28. B. Pinocytosis
• Cell drinking: droplets of extracellular fluid
are absorbed into the cell by small vesicles.
vesicles
• Example:
1. Fungi
Food Particles
Hyphae

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