AS Biology. Foundation. Cell membranes and Transport

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Methods of Transport Across Membranes

1. Diffusion

2. Osmosis

3. Facilitated Diffusion

4. Active Transport

AS Biology. Foundation. Cell membranes and Transport

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Solution Review

Solutions are made of solute and a solvent

Solvent - the liquid into which the solute is poured and dissolved. We will use water as our solvent today.

Solute - substance that is dissolved or put into the solvent. Salt and sucrose are solutes.

AS Biology. Foundation. Cell membranes and Transport

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1.Passive transport = no energy used

2. Molecules move from high concentration to low concentration

Diffusion-movement of molecules down a concentration gradient

http://www.youtube.com/watch?v=VY0mZUDvbH4

AS Biology. Foundation. Cell membranes and Transport

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Osmosis- movement of water down a concentration gradient

1.Passive transport =no energy used

2. Water moves from high concentration to low concentration due to solute concentration

http://www.youtube.com/watch?v=w3_8FSrqc-I

http://leukophobia.files.wordpress.com/2008/01/gummi-bear.jpg

AS Biology. Foundation. Cell membranes and Transport

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Hypotonic Solution - solution has a lower concentration of solute outside of cell than inside cell.

Hypertonic Solution - solution has a higher concentration of solute outside the cell than inside cell.

Isotonic Solution - both solutions have same concentrations of solute.

*Predict what will happen to an animal and plant cell when put into each solution.

Examples of Osmosis

http://www.biologycorner.com/resources/beakers_solutions_ABC.png

isotonic hypotonic hypertonic

AS Biology. Foundation. Cell membranes and Transport

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Plant and Animal Cells put into various solutions

Facilitated DiffusionNo use of energy

It requires protein molecules to transport molecules across the membrane

Proteins are specific to the molecules they transport

The molecules move from an area of high concentration to an area of low concentration.

-SUGAR and charged molecules pass across the cell membrane by this method of transport

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

Carrier Proteins Carry Molecules Across the Membrane

Good Example - transport of Glucose into the cell

Affects on the Rate of Diffusion

Temperature

Medium in which diffusion takes place

Size of solute concentration

http://www.austincc.edu/biocr/1406/labm/ex5/images/Diffusion_animated.gif

“Yellow food coloring diffusing through water. The glass on the left contains hot water, while the glass on the right contains cold water. The food coloring was added to the cold water slightly before the coloring was added to the hot water, yet after a few seconds it has diffused more thoroughly through the hot water. The frames are roughly 1 second apart (so the animation is roughly 2x real-time).”

Active Transport11

Active transport-requires energy – ATP is used directly or indirectly to fuel active transport-moves substances from low to high concentration-requires the use of carrier proteins

Active Transport12

1. Protein pump-an active transport mechanism

-ATP energy is used to change the conformation of the carrier protein

- large ions (Na+ or K+) are carried across the membrane that are traveling from low to high concentration

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

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Bulk Transport- Active14

2. Endocytosis occurs when the plasma membrane envelops food particles and liquids.

Phagocytosis (particles)Pinocytosis (liquids)

3. Exocytosis occurs when material is discharged from the cell.

-vesicles in the cytoplasm fuse with the cell membrane and release their contents to the exterior of the cell

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Endocytosis (white blood cell takes in bacteria to destroy it

16Exocytosis- let big bulk items out of the cell

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120068/bio02.swf::Endocytosis%20and%20Exocytosis