Transcript Transport and Osmosis PPT

OPEN UP TO YOUR
OSMOSIS AND
WATER POTENTIAL
TUTORIAL
The value for ψ in a plant cell was found to be -4 bars.
You place this plant cell in a 0.1M NaCl solution at 20⁰C in an open beaker…
1. What is the ψs of the solution?
2. What is the overall ψ of the solution?
3. Will the net flow of water be in or out of the cell?
Diffusion
 Diffusion

movement of molecules from HIGH  LOW
concentration (until equilibrium is reached)
diffusion
Transport
•
Passive Transport
– The passing of materials through the membrane
without using energy
– Going with the flow
(concentration gradient: high to low concentration)
Concentration Gradient
Simple Diffusion
• Type of Passive Transport
• When small, hydrophobic molecules can pass through the lipid bilayer rapidly
• Does not to use a protein
• Easy because the hydrophobic molecules don’t get rejected when
passing through the hydrophobic region.
– Examples: O₂, and CO₂
Facilitated Diffusion
 Type of Passive Transport
 Uses a CHANNEL or CARRIER PROTEIN to transport ions and
hydrophilic molecules across the plasma membrane
 Examples: Aquaporins that carry water
HIGH
facilitated = with help
open channel = fast transport
LOW
Passive Transport
- Does NOT use energy
- “Goes with the flow”
- Some types use proteins/others do not
• In a cell, water always moves across the membrane
toward a higher concentration of materials in order to
dilute it…or lessen the concentration.
• The diffusion of water across a selectively permeable
membrane is called osmosis.
• During osmosis, water diffuses across a selectively
permeable membrane to even out
CONCENTRATION of dissolved particles.
A cell always works
to make the
concentration of
dissolved material
equal on both
sides of the
membrane.
What do you
notice about
the amount of
dissolved
material
(concentration
of red dots) on
each side?
Selectively
permeable
membrane
Decide with your
neighbor which
way the water
would need to flow
in order for that to
happen?
• Notice the number of dissolved molecules did not change on
each side, but the amount of water changed.
• The CONCENTRATION on both sides is now more equal
ISOTONIC
• An isotonic solution has the
same concentration of
dissolved substances on
either side of the plasma
membrane.
Water Molecule
Dissolved Molecule
Isotonic solution = same concentration on both
sides
ISOTONIC
• This plant cell has its
normal shape and
pressure in an isotonic
solution.
• This is an animal blood
cell in an isotonic
solution.
• Water moves in and out
at an equal rate
HYPOTONIC
Hypotonic solution = Low concentration of solute
• If a cell is placed in a
hypotonic solution, the
concentration of
dissolved substances is
lower in the solution than
the concentration inside
the cell.
HYPOTONIC
• Plant cells swell
beyond their normal
size as pressure
increases(become turgid, full)
• Since animal cells don’t
have a hard cell wall
like plants, they could
burst if too much water
enters
HYPERTONIC
• If a cell is placed in a
hypertonic solution, the
concentration of
dissolved particles in
the solution is higher
than inside the cell.
Hypertonic solution = Higher concentration of solute
HYPERTONIC
• Plant cells lose
pressure as the
plasma membrane
shrinks away from the
cell wall.
(plasmolysis = wilt)
***can recover***
• Animal cells shrink up
like raisins.
DISCUSS WITH YOUR NEIGHBOR HOW EACH SOLUTION AFFECTS CELLS.
In Isotonic solution
In Hypotonic solution
In Hypertonic solution
Active Transport
- Requires energy
- “Goes AGAINST the flow” (Low to High Concentration)
- Must use a specific protein/ or enters as bulk flow
How about large molecules?
• Moving large molecules or bulk material into &
out of cell
– through vesicles
– endocytosis
– exocytosis
exocytosis
TRANSPORT of LARGE
MOLECULES
 Endo-cytosis is a process by which a cell membrane
surrounds and takes material INTO the CYTOPLASM.
TRANSPORT of LARGE
MOLECULES
 The material is engulfed and enclosed by a
portion of the cell’s plasma membrane.
TRANSPORT of LARGE
MOLECULES
 Exo-cytosis is the expulsion or secretion of large or
a bulk of materials from a cell.
Inside the cell
Outside the cell