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Cell Membrane Structure
Lipid bi-layerProteins imbedded as channels for transfers
Selective PermeabilitySelective Permeability
Property of cell membrane
Allows some substances in/out
Cells need nutrients/oxygen in
Cells need carbon dioxide/wastes out
Particles of matter in constant motion.
Solid particles move less than liquids & gases.
Particles move from crowded areas to less crowded areas until equilibrium is reached (evenly dispersed)
Background Information
- net movement of molecules from areas of HIGH concentration to LOW concentration
Diffusion Definition
Diffusion Example
Diffusion of perfume in a classroom!
The Diffusion Applet
Facilitated Diffusion
Carrier protein: molecules in cell membrane that “help” substances move in/out of cell
Specific protein for each moleculeType of Passive TransportUsed for:
– Molecules too large for fluid membrane– Molecules not soluble in lipid bilayer
animation
Osmosis
Osmosis:Osmosis: movement of water across cell membrane
• from high concentration to area of lower concentration
-AKA the diffusion of water.
Osmosis: Diffusion of Water
“Solution” for your Transport
Solution is:– A solute dissolved in a solvent
Solvent is:– Generally is water in living systems
Solute is:– Glucose, oxygen, salt etc; that which is dissolved in
the solvent
WHAT IS THE SOLVENT AND WHAT IS THE SOLUTE WHEN YOU MAKE JELLO???
What is concentration?
Mass of solute in a given volume. (example: g/L)– 30 grams of solute in 2 liters of water: 30 g/ 2 L OR 15
g/L
Which of the three has the greatest concentration?– 30 grams of sugar in 5 L of water– 20 grams of sugar in 40 L of water – 50 grams of sugar in 25 L of water?
Concentration Gradient
The difference in the concentration of molecules across a space.
Molecules are said to move down a concentration gradient.
What happened here?
Draw a sketch of the solutions:
Hyper vs. Hypo
Hypertonic – The solution with a higher concentration of solute in it. Hypotonic – The solution with a lower concentration of solute in it.
Isotonic – solutions which have equal concentrations of solute.
Direction of OsmosisIsotonic: Cell and environment have equal concentration of solute
Hypotonic: Cell has a lower concentration of solute than the environment
Hypertonic: Environment has higher concentration of solute than the cell
20% salt
80% salt
Plasmolysis
O Shrinkage cytoplasm inside the cell membrane
O Due to the loss of water from a plant cell
O Causes plants to wilt - Loss of inside cell pressure: Turgor Pressure
Dealing With Osmosis
Contractile Vacuoles (protozoa)– Pumps excess water out
Plasmolysis (plant cells)– Water loss; turgor pressure drops
Cytolysis (animal cells)– High turgor pressure; cell explodes
Passive TransportPassive Transport
movement down concentration gradient
cells do not use energy;- particles move by kinetic energy
includes: diffusion, osmosis, facilitated diffusion
Active TransportActive Transport
- Movement from LOW concentration to HIGH concentration (UP concentration gradient!)
- Cells use energy (ATP)
Example: plant roots pull in minerals from soil
Active v.s. Passive Transport
EndocytosisEndocytosis
- Cell membrane:o surrounds a substanceo pinches offo forms a vesicleo brings substance IN
-Includes:o Phagocytosis o Pinocytosis
Phagocytosis 1 2 3
Phagocytosis
ExocytosisExocytosis
Vesicle contents are released at the cell membrane
Application of Diffusion / Osmosis
Dialysis
o Kidney job: filter wastes from your blood
o Damaged kidney hook patient up to dialysis
- Blood is run from body to dialysis machine
- Machine filters out wastes by diffusion.
- Cleansed blood is returned to the body
Kidneys
Fish Gill FunctionThis is a close-up of a thin channel in the fish's gills. Water flows through it and is surrounded by blood vessels, that flow in opposite direction. The oxygen leaves the
water, and goes into the blood. From there, it is carried all around the body of the fish!