Transport through the

Cell Membrane

Passive TransportMovement across a cell membrane that does not require energy

2 examples:Diffusion

Osmosis

DiffusionMovement of a substance from areas of higher concentrations to areas of lower concentrations

Ex. Food coloring in water

Concentration GradientDifference in the concentration of a substance

Equilibrium

Concentration of a substance is equal throughout an area

Facilitated DiffusionType of passive transport that uses proteins to move substances down their concentration gradient.

Ex: There are specific proteins that help move sugars into the cell

Ion Channels

OsmosisDiffusion of water

http://www.watchknow.org/Video.aspx?VideoID=5165 - Osmosis in lettuce

Why should you gargle with salt water when you have a sore throat?

Answer

Pain caused by swelling of throat tissues (these contain water)

Salt water has a lower concentration of water than the throat tissues.

When a person gargles with salt water, the water from the throat tissues moves to the salt water.

Loss of water from throat tissue results in less swelling and pain.

Question

Why do plants along side of the road die after a winter where roads were heavily salted? Explain in terms of osmosis.

Answer

The higher than normal amount of salt in the plants’ environment causes their cells to lose water through osmosis.

Their leaves begin to look they have been through a very hot, dry summer.

Eventually the plants die because they do not have enough water to live.

Question

Why do wooden drawers of a dresser become sticky after a rain storm or a high humidity day? Explain in terms of osmosis.

Answer

On very wet days, wooden drawers in dressers absorb water from the air because of osmosis. This absorption warps the wood, making the opening and closing of drawers difficult. In drier weather water is lost from the wood, and the drawers return to their normal size.

Movement of Water

Solute: the substance that is dissolved in a solution, the smaller amount.Solvent: dissolves the solute in a solution, the larger amount

Ex: Make a solution of saltwater.Solute: SaltSolvent: Water

Water is the universal solvent.

Hypertonic solution: solution is more concentrated (more solute), water moves out of the cell

Hypotonic solution: solution has a lower concentration (less solute) water moves into the cell

Isotonic: concentration is equal (equal amts of solute), no water movement

Hypertonic, Hypotonic and Isotonic Solutions

If the fluid outside the cell has……

ThenOutsideFluid is……

Waterdiffuses……

Effect on Cell

Higher solute concentration than the inside

Hypertonic Out of cell Cell Shrinks

Lower concentration than the inside

Hypotonic Into cell Cell swells

Equal concentration to the inside

Isotonic Equally Cell stays the same size

Questions

1. Why are green leafy vegetables sprinkled with water at the supermarket?

2. Why is salt sometimes used to preserve food?

3. Why should you not drink sea water?

Answers

1. This prevents them from wilting due to water loss

2. Because a salt solution is hypertonic , the microorganisms present on the foods shrink and die.

3. Sea water contains high concentrations of solutes. Cells in the body lose water because of osmosis, possibly causing death.

http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.html

Active TransportChapter 4.2

Active Transport

Transport of substances against their concentration gradient, uses energy

Energy is in the form of ATP Adenosine Triphosphate

Carrier proteins help move substances

Sodium-Potassium Pump

Transports sodium and potassium Ions against their concentration gradient

Chapter 4

Cells and Their Environment

Sodium-potassium pump

pumps three

sodium ions

out of the cell

pumps two

potassium ions

into the cell

Sodium Potassium Pump

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120068/bio03.swf::Sodium-Potassium%20Exchange%20Pump

Movement in Vesicles

Many substances, such as proteins and polysaccharides, are too large to be transported by carrier proteins.

These substances are moved across the cell membrane by vesicles.

Movement in Vesicles

Endocytosis: movement of a substance into the cell.

Cell membrane forms a pouch and pinches off

Exocytosis: movement of a substance out of the cell

Vesicles fuse with the cell membrane and empty their contents outside the cell.

Endocytosis

Exocytosis

Review of Cell Processes

http://highered.mcgraw-hill.com/olc/dl/120068/bio02.swf Exo and Endo animation

http://www.classzone.com/cz/books/bio_07/get_chapter_group.htm?cin=2&rg=animated_biology&at=animated_biology&var=animated_biology

http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.html