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!