CELL TRANSPORT

HomeostasisMembrane permeability

EquilibriumTransport

Homeostasis:Maintaining a Balance

Organisms must adjust to changes in their environment.

If not…DEATH!

What Maintains Homeostasis?

The PLASMA MEMBRANE maintains the proper concentrations of materials by controlling the passage.

Characteristics of the Cell

Membrane

Selectively Permeableaka Semipermeable

1.Water, oxygen, nitrogen, carbon dioxide and other small nonpolar molecules can diffuse directly

2.Allows some things in and others not

Plasma Membrane-Structure

1. Phospholipid Bilayer-2. 2 fatty acids and 1 phosphate group

attached to a glycerol3. Polar Heads (water

soluble)4. Non Polar -Fatty acid

chain (not water soluble)

REVIEW NOTES FROM THE CELL!

The cell The cell membrane also membrane also has has proteins proteins floating in it floating in it that do many that do many things. Some things. Some are gates to let are gates to let substances in substances in and out. and out.

Protein in Protein in membranemembrane

Plasma Membrane Function-Proteins

• The cell membrane's function, in general, revolves around membrane proteins.1. Receptor proteins which allow cells to communicate

2. Transport or channel proteins regulate what enters or leaves the

cell

3. Marker proteins which identify the cell

Cellular Transport

NO ENERGY REQUIRED• Diffusion (passive)• Facilitated Diffusion (passive)• Osmosis-Diffusion of Water (passive)

ENERGY REQUIRED• Active Transport

DiffusionDiffusion - the process by which molecules spread from areas of high concentration, to areas of low concentration.

Passive Transport-requires no energy

•Concentration gradient - a difference between concentrations in a space.

• C. When the molecules are even throughout a space - it is called Dynamic EQUILIBRIUM

About this diagram: this represents a cell in a solution. The cell will not let the red particles pass through the membrane. The green molecules can pass through, as can water molecules. The arrows show the direction of particle movement. The green particles are moving in to the cell where their concentration is lower, and water is moving out of the cell because its concentration is higher inside

osmosis

diffusion

OsmosisA. Osmosis - the diffusion of watermolecules through a selectively permeable membrane. Passive Transport

Ex.Water will move in the direction

where there is a high concentration of solute (and hence a lower

concentration of water).

Isotonic Solution

•Concentration of solute in cell and solution is equal

•No net movement into or out of cell

Hypotonic Solution

There are less solute (salt) molecules in the solution.

Water will move into the cell.

Cell will swell Cell could burst Plant cells have

vacuoles to collect extra water

Hypertonic Solution

A.There are more solute (salt) molecules in solution, which causes the water to leave the cell

B.Plants wilt and animal cell shrink-Plasmolysis. In both cases, the cell may die.

Crenated red blood cells in hypertonic salt solution

X 1000

Notice that the cells have shrunk.

Red blood cells in isotonic solution

X 1000

Note that all the cells appear normal.

Red blood cells in hypotonic solution

X 1000

Note that the pinkish cells have swollen (the little dip in the middle of a normal rbc is not visible and one side bows out).

Facilitated Diffusion (Transport Proteins, passive)

• Moves substances down the concentration gradient without using cell’s energy

• Use of carrier proteins located in membrane

Animations of cell processes:

Diffusion & Osmosis:

http://www.biologycorner.com/bio1/diffusion.html#

Osmosis Examples

http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm

Hypotonic, Hypertonic, Isotonic Interactive Quiz

http://www2.nl.edu/jste/osmosis.htm#Osmosis

Active Transport

Move particles from a region of lesser concentration to a region of greater concentration. Move against the concentration gradient. Must use energy (ATP)

Sodium-Potassium Pump

Sodium/Potassium pump:

3 Na+ out of cell

2 K + into cell

Here the energy of a phosphate (shown in red) is used to exchange sodium atoms for potassium atoms.

Endocytosis and Exocytosis

Cells can also move things in and out by using pieces of membrane. Look at the animations on the link to

view these processes:

Endocytosis:

pinocytosis – cellular drinking phagocytosis – cellular eating

Exocytosis:

- can involve getting rid of waste, or can involve secreting cell products (such as hormones or other important compounds)

Active TransportExocytosis

Exocytosis- substances inside a vesicle are released from a cell as the vesicle fuses with the cell membrane

• Requires Energy

Endocytosis

Substances are moved into a cell by a vesicle that pinches off from the cell membrane

Phagocytosis-cell “eating” engulfs food

Pinocytosis- cell “drinking” Requires energy

ATP