Cellular Transport

On the following slides, the blue sections highlight the main points; summarize the slides for your notes. Underlined words = vocabulary!

Plasma MembraneAKA Cell Membrane

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

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:– Proteins are used in

transport– Cholesterol stabilizes the

phospholipids– Carbohydrate chains are

markers, think “ID” tags

What is a concentration gradient?

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

The concentration gradient measures the amount of solutes in the fluid within and out of a cell Simulation

http://cnx.org/resources/160ffab563fb667fb2ab5475bde02fb1/Figure_03_05_01.jpg

What is diffusion? 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 or carrier proteins imbedded in the plasma membrane as “doorways”.

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

What is osmosis? Water is one of the most

important nutrient that cells need in order to function.

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

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

Passive vs Active Transport

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

Active transport is when cells uses energy to move molecules against the concentration gradient . – Carrier proteins act as

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

http://www.daviddarling.info/images/active_transport.jpg

http://iws.collin.edu/biopage/faculty/mcculloch/1406/outlines/chapter%208/8-14.jpg

Label: High vs low

concentration for each of the three scenarios

Diffusion Facilitated

diffusion Active

transport

Knowledge Check

Take a deep breath! How does oxygen get into

your blood stream? How does it “diffuse”?

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?

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

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 travel out and it will shrink.

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

Solutions and Cells

Sketch the graphics (be sure to include the H2O arrows!!!)

http://2.bp.blogspot.com/_10M5kCPMTYM/S-1kTAlmmrI/AAAAAAAAABc/Duc-LSzYgyU/s1600/Bio+hypotonic,+Isotonic,+Hypertonic.gif

I”S”otonic = “S”ame!

Hype”R”tonic – The cell

sh”R”inks!

Hyp”O”tonic – The cell

gr”O”ws!

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.

What is phagocytosis? 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

Video1 Video 2

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

Limitations to Cell Size

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 DNA, instructions 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).

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.

http://highered.mcgraw-hill.com/sites/dl/free/0078757134/383917/bz.gif