Anticipatory Set 9-15-11
Anticipatory Set 9-21-11 L2&3
Cellular Transport
Selective Permeability
⌂ Selective permeability- the cell
membrane’s ability to allow some
substances to enter/ exit but not all.
⌂ Two processes that allow substances
to enter/exit:
• Passive transport – energy from kinetic
energy and concentration gradient.
• Active transport-ATP
Diffusion
⌂ Process depends on concentration gradient.
• Particles will never stop moving, but when
equilibrium is reached there will be no net change
in their concentration.
• Movement of particles is from [high] to [low]
concentration.
• Dependent on four factors: diameter,
temperature, electrical charge (when applicable),
and the concentration gradient.
• Majority of materials enter cell through
diffusion…energy conservation for other
processes.
Cell Membrane & Diffusion
⌂ diffusion animation
Osmosis
⌂ Diffusion of water.
⌂ Water always travels
from hypotonic to
hypertonic
⌂ Solute always travels
in opposite direction
of water.
⌂ Osmosis Animation
Isotonic Solutions
⌂ Isotonic solutions-the
same amount of
solute exists inside
and outside the cell.
⌂ Water moves in and
out at the same rate.
Hypertonic Solutions
⌂ Hypertonic solutionshave more solutes in
solution than inside
the cell.
⌂ Water moves out of
the cell to achieve
equilibrium.
Hypotonic Solutions
⌂ Hypotonic solutionshave less solutes in
them than inside the
cell.
⌂ Water will enter the cell
to try and achieve
equilibrium.
⌂ Cells may lyse if too
much water enters.
⌂ Plants combat this risk
with their cell wall, and
turgor pressure results.
Data Set 9
Level 1 and 1
Level 1 & 2
Level 1, 1, 2
Osmoregulation-water control
⌂ Turgid- enough water,
plant cell rigid
⌂ Flaccid- lacking
water, plant cell limp
⌂ Plasmolysis- cell
membrane is ripped
from cell wall
.
Hypotonic solution
Isotonic solution
Hypertonic solution
Animal
cell
H2O
H2O
Turgid (normal)
H2O
H 2O
Flaccid
H2O
Shriveled
Normal
Lysed
Plant
cell
H2O
H2O
H2O
Plasmolyzed
Water Potential- water’s ability to do
work when going through the C.M.
⌂ Pressure Potential
• Positive pressure is the
cell being pushed
• Negative Pressure- the
cell being pulled (eg
transpiration)
⌂ Solute Potentialbased on solute
concentration
Positive Pressure Potential
Positive Pressure
Potential
Negative Pressure Potential
Negative Pressure
Potential
Solute Potential
ΨS = -iCRT
-i (ionization constant)
C (molar concentration)
R (pressure constant)
T (temperature in Kelvin)
Turgor pressure is ~100psi, much more than a
tire. The pressure is so great that plant cells
would detach from one another if not for
adhesive molecules known as pectins.
Facilitated Diffusion with Channel
Proteins
⌂ Facilitated diffusionwithin the cell membrane
are channel proteins that
allow materials to pass
into the cell.
⌂ Aquaporins- channel
proteins that allow water
to pass through, in
addition to simple
diffusion.
• In kidneys and plants where
water is essential
• Channel Protein Animation
FD with Ion Channel Proteins
⌂ Channel protein let in ions.
⌂ When the protein shape changes, the gate
will open.
⌂ Ions pass through based on size and charge.
⌂ Can be ligand gated or voltage gated.
⌂ Voltage gated channels depend on two
things:
• Concentration gradient of K
 Concentration of K (usually higher inside cell)
• Membrane potential due to charge imbalance.
Anticipatory Set 9-22-11
Level 3
Facilitated Diffusion with Carrier
Proteins
⌂ Carrier proteins
transport polar
substances like amino
acids and sugars.
⌂ When the carrier
proteins become
saturated the rate of
diffusion is maxed out.
⌂ Animation: How
Facilitated Diffusion
Works
Figure 5.12 A Carrier Protein Facilitates Diffusion (Part 1)
Filtration
⌂ Filtration- pressure
driven system that
pushes water and
nutrients across cell
membranes.
⌂ This is how urine is
produced
⌂ Does not require
energy.
Active Transport
Active Transport is Directional
⌂ Active transport always works against the
concentration gradient. Going from a lower
to higher concentration.
⌂ Requires energy.
⌂ Two types: primary and secondary active
transport.
Membrane Proteins associated with
Active Transport
⌂ Cell Pumps:
⌂ Uniports move a single substance in one
direction.
⌂ Symports – move two substances in the same
direction.
⌂ Antiports - move two substances in opposite
directions. One into the cell, and one out of the
cell.
• e.g. NaK pump
• Coupled transporters are those that move two
substances. Which of these are coupled?
Figure 5.13 Three Types of Proteins for Active Transport
Primary Active Transport
⌂ ATP is hydrolyzed and drives the movement of
ions against the concentration gradient.
⌂ Sodium potassium pump is an example of 1AT.
Because the ions move against the concentration
gradient. (Na leaves cell, although more Na
outside cell, same with K more in cell, but K still
enters)
⌂ NaK Pump located in all animal cells; antiport;
coupled transporter
⌂ NaK Pump Simple Animation
⌂ Na K Pump Animation
Figure 5.14 Primary Active Transport: The Sodium–Potassium Pump
Membrane Potential
⌂ Membrane Potential aka Voltage
Gradient allows the cell to do work.
⌂ DNA is negative inside cell(-), NaK
pumps extra Na out of the cell (+).
⌂ Difference in charge allows
molecules to be transported using
ATP.
⌂ E.g. glucose enters through because
of membrane potential
⌂ Secondary AT Animation
H Pumps
⌂ Most important pump for cell
respiration and photosynthesis.
⌂ H+ pumped out of cell, and ions
can now diffuse in
⌂ Pumping H requires little
energy, and they help sugars
enter the cell by AT
What if the macromolecules are too
large, charged, or polar to enter
through the membrane?
⌂ Is this a good problem or not?
⌂ Which organelle is responsible for substance
transport?
Endocytosis
⌂ Processes that bring substances
into the cell such as
macromolecules and smaller cells.
⌂ Three types of endocytosis:
• Phagocytosis
• Pinocytosis
• Receptor-Mediated Endocytosis
Figure 5.16 Endocytosis and Exocytosis (A)
Phagocytosis
• Cell eating
• Part of cell membrane engulfs particles/cells
• Phagosome fuses with a lysosome and digestion occurs
Endocytosis
⌂ Phagocytosis- process fairly nonspecific
⌂ Only a few cells can do this ex. WBC
• Must be able to change shape and form
pseudopodia.
• WBC will attach to bacteria engulf bacteria
with pseudopodia lysosomes with enzymes
digest it residual waste is exocytosed.
• Pinocytosis- same process just with liquids.
Also fairly nonspecific.
• WBC and Phagocytosis Animation
Receptor-Mediated Endocytosis
⌂ Specific process that utilizes integral membrane
proteins to bind to specific molecules in the cell’s
environment.
⌂ Receptor proteins are substance specific, aka
coated pits. Coated with protein , formed by CM
depressions.
⌂ When a ligand binds to the receptor protein, it
invaginates and forms a vesicle.
⌂ E.g. cholesterol uptake in mammals rd. 113-114
Figure 5.17 Formation of a Coated Vesicle (Part 1)
Figure 5.17 Formation of a Coated Vesicle (Part 2)
Receptors will form a new
vesicle and be recycled back to
plasma membrane.
Exocytosis
⌂ Anything that comes in must go
out.
⌂ Materials are packaged into
vesicles, which fuse with the cell
membrane via a membrane
protein.
⌂ The two membranes fuse, contents
expelled, and the CM incorporates
vesicle membrane.
Endocytosis and
Exocytosis Animation
Hyper,Hypo,Iso
Other Cell Membrane
Functions
⌂ Some organelle membranes help
transform energy.
⌂ Some membrane proteins organize
chemical reactions.
⌂ Some membrane proteins process
information.
Plasmolysis
⌂ Net loss of a cell’s volume due to a
hypertonic environment.
⌂ Plasmolysis Animation
Water Potential
⌂ Tendency of water to leave one place in favor of
another.
⌂ Always moves from higher to lower water potential.
⌂ Affected by pressure and solute
⌂ Water potential () = pressure potential (p) + solute
potential (s)
⌂ Solute Potential = s=–iCRT
• i = The number of particles the molecule will make in
water; for NaCl this would be 2; for sucrose or glucose, this
number is 1
• C = Molar concentration (from your experimental data)
• R = Pressure constant = 0.0831 liter bar/mole K
• T = Temperature in degrees Kelvin = 273 + °C of solution
⌂
Water Pot. and
Plasmolysis
Lab: Plasmolysis
⌂ Perform a serial dilution of salt (100, 50, 25,
0% solution)
⌂ Predict which solution will yield the fastest
plasmolysis results.
⌂ Perform Experiment with each solution and
time results.
Lab: Water Potential
⌂ Perform a serial dilution of sugar ( 100, 50,
25, 0). Label solutions.
⌂ Core equal lengths of 2 vegetables.
⌂ Record lengths, mass, and vegetable type in
table.
⌂ Predict what will happen to length and
mass by tomorrow.
Anticipatory Set 10-10-11 Level 2