Unit #4Cellular Transport

The blue sections summarize key information and vocabulary terms are underlined.

Plasma MembraneTextbook Reference pg. 176-177

http://droualb.faculty.mjc.edu/images/Anatomy/Cytology/FG02_05.jpg

Video

http://www.theresedesjardinstudio.com/images-art-paintings-prints/Dons-images-graphics-photo/8MOSAIC.BIRD.OF.PARADISE-1A.jpg

Fluid Mosaic Model

Textbook Reference pg. 178

Plasma membranes are commonly described as a fluid mosaic model; it is made of various molecules in a complicated phospholipid bilayer.

The plasma membrane is fluid, embedded with trans-membrane proteins, cholesterol, carbohydrate chains. – Proteins are used in transport– Cholesterol stabilizes the

phospholipids– Carbohydrate chains are

markers, think “ID” tags

Solutes versus Solvents Textbook Reference pg. 149

Cells have to move things through membranes on a regular basis (food, water, waste, etc.).

The concentration measures the amount of solute in a solvent (stuff in it, EX sugar in tea).Simulation

http://universe-review.ca/I12-18-solution.jpg

What is diffusion?Textbook Reference pg. 154-156, 198-199

In a solution, the particles are moving constantly (in a glass of water, molecules are still moving).

Diffusion is the movement of particles from a high concentration to a lower concentration to reach equilibrium (relatively the same or equal on all sides).

Facilitated diffusion is the process by which cells uses channel proteins or carrier proteins imbedded in the plasma membrane as “doorways”.

http://www.okc.cc.ok.us/biologylabs/Images/Cells_Membranes/diffusion.gif

Knowledge Check

Take a deep breath! How does oxygen get into your blood

stream? List your thoughts on the above question.

Your answer must include:: – Where is oxygen MOST concentrated? – Where is oxygen LEAST concentrated? – Where will the O2 diffuse? Why?

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What is osmosis? Textbook Reference pg. 195-196

Water is one of the most important items that cells need in order to function.

Osmosis is the diffusion of water through a selectively permeable (to permeate is to pass through) membrane.

The rate of osmosis is controlled by the concentration of solutes in a cell’s environment.

Water will move easily, until the concentration is relatively equal on both sides of the cell membrane.

http://www.okc.cc.ok.us/biologylabs/Images/Cells_Membranes/osmosis.gif

Hypotonic solution has a higher solute concentration inside the cell, so water will travel in to the cell (grow).

An isotonic solution (or “same strength”) is one where the concentration inside the cell matches the outside of the cell – there is equitable movement in and out.

Hypertonic solution has a higher solute concentration outside the cell, so water will move out of the cell and it will shrink.

http://biology.unm.edu/ccouncil/Biology_124/Images/tonicity1.jpeg

Solutions and Cells Textbook Reference pg. 196-197

Sketch the graphics (be sure to include the arrows!!!) Click on the simulations to view diffusion and osmosis. Simulation #1

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Hyp”O”tonic Solutions – The cell gr”O”ws!

Hype”R”tonic Solutions – The cell sh”R”inks!

I”S”otonic = “S”ame!

Knowledge Check Examine the diagram to

the right. Turn to your neighbor

and answer the following questions: : – Where is water

MOST concentrated in the top cell?

– Where is water MOST concentrated in the bottom cell?

– How will the cells change in the next as a result of the above?

"Osmosis, cellular process of." Experiment Central. U*X*L, 2010. Science In Context. Web. 26 Sept. 2013.

Passive Transport vsActive Transport

Textbook Reference pg. 198-199

Diffusion and osmosis are processes within the cell that occur naturally, without the need for energy; they are forms of passive transport.

Active transport is a process by which cells uses energy to move molecules against the concentration gradient . – Carrier proteins within the plasma membrane act as

“doorways” to move molecules and substances in and out of the cell against the gradient (from a low concentration to a high concentration). Video

http://www.daviddarling.info/

images/active_transport.jpg

What is phagocytosis? Textbook Reference pg. 200

Phagocytosis: the process when cells move shift the cytoplasm to surround a substance; means “cell eating”– Endocytosis = cell surrounds and takes in material – Exocytosis = cell expels wastes

Video

http://static.howstuffworks.com/gif/artificial-blood-8.jpg

Limitations to Cell Size Textbook Reference

pg. 200-203

In order for cells to diffuse materials easily in and out of their membranes, their size has to remain relatively small.

1. Diffusion - if cells are too large, it would take entirely too long for the materials to diffuse and reach their destinations.

http://cnx.org/content/m44406/latest/Figure_04_02_02.jpg

Size Limitations Cont.

2. Proteins - The nucleus within eukaryotic cells carries genetic information embedded with the DNA molecule to make proteins; these proteins are needed throughout the cell (in almost all organelles) and for important functions.

The cell must stay small because proteins could not be made quickly enough to meet the demands for a large cell.

http://2.bp.blogspot.com/_hhUdKwzDmA4/S7dXzoiCGiI/AAAAAAAAAhM/XiFyUjna6NQ/s1600/nucleic+acid.jpg

Size Limitations Cont.

3. Surface Area - As cells increase in size, the volume within them increases as well (the surface area to volume ratio).

The surface area is the sum of all the areas of all the shapes that cover the surface of the object.

As the volume increases, the need for materials is much greater than the surface area available to diffuse oxygen, nutrients, and expel wastes.

Cells must, therefore, remain small.

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