Fluid Mosaic Model
• Current model of the membrane structure.
• Phospholipids fluid sea in embedded with a
wide variety of protein molecules.
Cell Membrane
• The cell membrane is also known as:
–Phospholipids bi-layer
–Plasma membrane
–Fluid mosaic membrane
What is a Solution?
• Is a homogeneous mixture
• A combination of a Solute and
Solvent.
• Large part is the solvent (water)
• Small part is the solute
What is a [ ] Gradient?
• Is the process of particles, which
the solutes is moving through a
solution from an area of higher
number of particles to an area of
lower number of particles.
[ High ] to [Low]
Concentration Gradient
High
Down
Low
Protein
Carrier
Carrier molecule
What can diffuse through?
• Small & nonpolar molecules
can diffuse through the cell
membrane
•CO2
•O2
Understanding solutions
• More Solvent
• Less Solute
• Less solvent
• More Solute
solute
solvent
Understanding solutions
Hypotonic solution
Hypertonic Solution
solute
solvent
Understanding solutions
• Hypotonic Solution
• Hypertonic solution
Cell
solute
solvent
Understanding solutions
• The solution has solvent and solute
• The cell has solvent and solute too.
solute
Who has more solute?
25% solute
75% solute
What type of solution is this cell in?
What will happen to this cell?
H 2O
Cell
Shrinks
Who has more solute?
85% solute
15% solute
What type of solution is this cell in?
Lysis
H2O
Cell
Swells or burst
Who has more solute?
40% solute
40% solute
What type of solution is this cell in?
Isotonic solution
60% water
40% solute
60% water
60% water
40% solute
60% water
The cell stays the same
Hypertonic Solution
Plant Cells
Animal Cells
Hydrophobic vs Hydrophilic
• Hydrophilic (attracted to water)
• Hydrophobic (not attracted to water but are attracted to
other hydrophobic tails)
• They have a hydrophilic phosphate head and two
hydrophobic hydrocarbon tails.
• Cell membranes are made up of a double layer of these
phospholipid molecules.
• The phospholipid bilayer makes the membrane very stable
but also allows flexibility.
• The phospholipid in the membrane are in a fluid state
which allows the cell to change it’s shape easily.
Osmotic Pressure
• The pressure of water moving
across a membranes cause by
a concentration gradient.
Turgor Pressure
• Is a hydrostatic pressure due to a
plant cell being placed in a
hypotonic solution.
• Is pressure on inside of a cell against
the cell wall.
• Only in plant cells
What is Plasmolysis?
• The Shrinking of cell membrane from
cell wall in a plant or bacterial cell,
caused by loss of water through
osmosis.
• from Greek lusis, a loosening.
What is Crenation?
• Crenation is the contraction of a cell after
exposure to a hypertonic solution, due to the
loss of water through osmosis.
• Crenation occurs because in a hypertonic
environment, osmosis .
• As a result the cell shrinks and forms
abnormal notchings around its edges.
What is cytolysis?
• Cytolysis, or osmotic lysis, occurs when a cell
bursts due to an osmotic imbalance that has
caused excess water to move into the cell.
• It occurs in a hypotonic environment.
• Where water moves into the cell by osmosis
where the volume exceeds the membrane's
capacity and the cell bursts.
• The presence of a cell wall prevents the
membrane from bursting, so cytolysis only occurs
in animal and protozoa cells which do not have
cell walls.
Active or Passive Transport
•
•
•
•
•
•
•
•
•
•
Active
Endocytosis
Diffusion Passive
Exocytosis Active
Osmosis Passive
Passive
Oxygen
Carbon dioxide Passive
Sugar Passive
Water Passive
Pinocytosis Active
Phagocytosis Active
Leaf Anatomy