Transcript Plasma Membrane

Plasma Membrane
Phospholipid
• Phospholipid Animations (3)
Phospho head
– polar
Lipid tail nonpolar
Phospholipid Bilayer
• Hydrophilic heads (water-loving)
Hydrophobic tails (water-hating)
Fluid Mosaic Model
• BBC Education - AS Guru - Biology - Cells
- Pathways - Plasma Membranes
Proteins in Membrane
Cholesterol: add stability to
membrane in higher temperatures
Carbohydrate Chain
Carbohydrate Chain: Used as
Identification Markers
PROTEIN JOBS:
attaches to cytoskeleton
PROTEIN JOBS:
• Enzymes which are catalytic teams for
molecular assembly lines
• A Biochemical Pathway (click on
animation)
• Biochemical Pathway Animation II (CLICKALSO CLICK ON ARROWS)
PROTEIN JOBS-Receptors:
enable cells to detect chemical
messages from other cells
PROTEIN JOB: Signal
Transduction
• Receptor binds to trigger a chain reaction
• EXAMPLE ANIMATION (CLICK ON
START AND NEXT) MAP Kinase Signal
Transduction Animation by Dr. Vic Lemas
at BioCreations
• Another Signal Transduction Animation
Interactive Concepts in Biochemistry Interactive Animations
Signal Transduction Diagram
Diffusion
• Movement of a substance
from a region of higher
concentration to a region of
lower concentration
Diffusion
• Scientific Method (diffusion animation)
Facilitated Diffusion
• A protein helps the substance (like an ion)
across the membrane
Facilitated Transport
• Facilitated diffusion involves the use of a
protein to facilitate the movement of
molecules across the membrane.
• Cell Animations (scroll down to Carriermediated passive transport Facilitated
transport)
Passive Transport
• Cell does not need to use energy
• Movement of molecules goes “down the
gradient” (from high to low concentration)
– Diffusion
– osmosis
– Facilitated diffusion
Active Transport
• During active transport, cell needs to use energy
(ATP) as molecules against a concentration
gradient (low concentration to high
concentration).
– endocytosis
– Exocytosis
– Pumps (USE ATP)
• Cell Animations (scroll down to active transport)
Comparing Active and Passive
Transport
• Shockwave Click here
Endocytosis
• The process by which a cell engulfs
material to bring it into the cell is called
endocytosis. A vacuole is formed that
contains the material that has been
engulfed.
Exocytosis
• Vesicle fuses with plasma membrane to
exit the material outside the cell
• (cell pooping)
Endocytosis Animation
• Endocytosis and Exocytosis Animation
• What is the difference between the two?
Which brings material in and which brings
materials out of the cell?
• Endocytosis is in
• Exocytosis is out
Diffusion: flow from high to low
concentration
• Also facilitated diffusion (protein channel)
Diffusion
Things that can pass freely through
the plasma membrane
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Hydrophobic molecules (oil soluble)
O2
N2
Nonpolar
Benzene
Small uncharged Polar molecules
H2O
CO2
Molecules that don’t pass
through the phospholipid bilayer
easily...
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Large uncharged
Glucose
Polar molecules
Sucrose
Ions (charged) H+ , Na+ , HCO3 , K+,
Ca+2,Cl- , Mg+2
So what three characteristics of a
molecule determine the
permeability of the membrane?
• Charge
• Size
• Polarity
• However: some molecules
which we would think
should (or should not) cross
the plasma membrane do (or don't) because of the
presence of the membrane
proteins.
Osmosis
• Osmosis is the movement of water
from a region of high water
concentration to a region of lower
water concentration through a
selectively permeable membrane.
• The Cell: Passive Transport
Osmosis - Learning - click
Solution Vocabulary
Solution = solvent + solute
Solute- what is
being dissolved
EX: salt
Solvent –
what is
doing the
dissolving
EX: water
Osmosis
• Scientific Method (animation)
Hypotonic Solution
• Osmosis (click for animation)
• A hypotonic solution is one
that has less solute (more
water).
• Cells in hypotonic solution
tend to gain water.
Isotonic Solution
• Osmosis (click for animation)
• the concentration of solute is the
same on both sides of the membrane
(inside the cell and outside).
• A cell placed in an isotonic solution
neither gains or loses water. Most
cells in the body are in an isotonic
solution.
Drag the bag
• Osmosis (predict what will happen)
• LabBench (do a little experiment)
Hypertonic Solution
• Osmosis (click for animation)
• A hypertonic solution is one
that has a high solute
concentration.
• Cells in a hypertonic solution
will lose water.
Plasmolysis
• Plant cells placed in
a hypertonic solution
will undergo
plasmolysis, a
condition where the
plasma membrane
pulls away from the
cell wall as the cell
shrinks.
• The cell wall is rigid
and does not shrink. before
Osmosis Lab
• Use grams on the scale.
• Be very careful when carrying (use a
spoon) and drying the egg (gently with a
paper towel).
• Two set-ups per lab table. (If one side
breaks, you have a back-up.)
• WHEN FINISHED: Clean beakers. Dry off
scale and turn off.
•Watch the
chloroplasts
• Plasmolysis of Elodea
• Also scroll down for
rehydration of elodea
Plant Cell Plasmolysis
Stiff Cell wall
Plasmolysis:
Flaccid:
Sunken in
Normal pressure
Cell wall
on cell wall
Turgid:
Lots of pressure
on cell wall
Can you tell which is the
plasmolyzed and which is normal
elodea?
Compare Plant Cells
Plasmolysis
• NORMAL CELL
water moves toward the area with
a higher solute concentration
because it has a lower water
concentration.
water moves from hypotonic to
hypertonic solution.
Red Blood Cells p. 83
Solutions
• If a cell is in
a Hypotonic
solution, the
cell will…
• lose water
• If a cell is in a
Hypertonic
solution, the
cell will…
• gain water
Turgor: pressure of water vacuole
on the cell wall of a plant
Active Transport
• Active Transport Animation
• Cell needs energy to move
particles “against the gradient” from low to high concentration
Active Transport
Active Transport
• "pumps" materials across the membrane
against the concentration gradient. i.e.
,from low concentration to high
concentration (therefore it requires
energy).
Endocytosis
• Endocytosis: Large materials transported
into the cell.
• Endocytosis includes three slightly
different processes:
– Phagocytosis
– Pinocytosis
– Receptor-mediated
Endocytosis
• Endocytosis - "to enter the cell"
• Phagocytosis - large particles - membrane
"reaches out" - phago = eat"
• Pinocytosis - solutes in fluids - membrane folds
in to form a pouch known as a vesicle. - pino =
drinking"
• Receptor mediated endocytosis - receptors on
the membrane attach to large molecules like
hormones and folds them inside.
Phagocytosis
• Animations:
• Phagocytosis
Engulfing large particles
“Cell eating”
• Phagocytosis |
Flash simulation,
Animation,
Illustration,
Picture, Diagram eduMedia
Pinocytosis
• “Cell drinking”
• Engulfing
small liquid
droplets
Receptor-Mediated Endocytosis
• Receptor Mediated
Endocytosis
• Specialized receptor
that just fits a specific
substance
• EX: LDL
• Hormones
• insulin
Receptor Mediated Endocytosis
Exocytosis
• Material (wastes etc.) are
expelled from the cell
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•
Table 8.2: Five processes by which substances move across cell membranes.
Simple
Diffusion
Facilitated
Diffusion
Particle
Movement
High to low
High to low
Active
Transport
Low to high
Exocytosis
Intracellularl to extracellular
Endocytosis Extracellular to intracellular
•
Protein
Carrier
Energy
Required
No
No
Yes
No
Yes
Yes
No, occurs by fusion
of vesicles with
cell membrane.
No,
occurs by involution of cell
membrane.
Exocytosis