HOMEOSTASIS and CELL TRANSPORT Chapter 5
Cells get things in and out using two methods PASSIVE TRANSPORT does NOT use energy ACTIVE TRANSPORT does use energy (ATP)
Passive Transport & Cell Membrane Cell membranes help organisms maintain homeostasis by controlling what may enter or leave. Selective Permeability only certain substance can go in and out http://connected.mcgraw-hill.com/connected/permlink.do?ced_pl_id=7jvn7g@3g52sg05pq@ztfmtv9@
Structure and Function The way the cell membrane is built determines what is allowed to go through Visit this site http://learn.genetics.utah.edu/ content/begin/cells/membrane s/
Molecules that can move (diffuse) across the membrane Some go straight through the bilayer*, others need to go through proteins Water Oxygen* Nitrogen* Carbon Dioxide* Small, non polar molecules* http://www.teachersdomain.org/asset/ tdc02_int_membraneweb/
What is the fluid mosaic model? Explain why the cell membrane is described as being BOTH FLUID AND MOSAIC. HINT do not google what is the fluid mosaic model? I did and the answers were unclear, confusing, unhelpful and not what we are looking for What SHOULD we search for?
What is the fluid mosaic model? Phrase used to describe the plasma membrane Fluid bcs the molecules are moving Mosaic bcs there are different parts that form patterns
Left Side Create Your Own diagram of the cell membrane This should be an original drawing of the cell membrane incorporating information from any worksheets or notes up to this points While it should be accurate you should also include common/analogy items to your picture to help you remember what is going on. For example next to the receptor proteins I may draw an old TV antenna going through the cell membrane (for you young ins you used to need an antenna to get good reception, it would receive the TV signal). What else sends or receives messages? Before you begin, organize your info what do you need to include?
The assignments must include color There should be a combination of pictures an explanations with text.
Remember use pictures, words and sentences to explain Glycoprotein Pore Fibrous proteins Cholesterol Channel Phospholipid (head, tail) water loving, water hating Selective permeability What substances can go through?
Illustrations can get complicated break it down into what you already know
PASSIVE TRANSPORT substances can cross the membrane without using energy Two types 1.Diffusion 2.Osmosis
PASSIVE TRANSPORT: DIFFUSION All molecules move constantly and randomly Concentration: amount of substance in an area You can tell how particles will tend to move if you know how crowded they are Particles will spread out until they are uniformly distributed Equilibrium concentration of molecules will be the same through the space
PASSIVE TRANSPORT: DIFFUSION Diffusion movement of molecules from an area of higher concentration to an area of lower concentration.
examples of diffusion
Demonstrations Diffusion in a Liquid Demonstration Use your sniffer
PASSIVE TRANSPORT: DIFFUSION CONT. http://www.johnkyrk.com/diffusion.html Not currently working. http://www.biosci.ohiou.edu/introbioslab/bios170/dif fusion/diffusion.html
PASSIVE TRANSPORT: DIFFUSION CONT. Interactive Learning at ewart.org.uk
OSMOSIS A Type of Passive Transport
Definition Osmosis The diffusion of WATER from an area of high WATER concentration to an area of low WATER concentration Most cells undergo osmosis because they are surrounded by watery solutions There are different concentrations of particles inside & outside of the cell Sugars, amino acids, ions
Movement of water Water will move from where this is a lot of water (conc) to where there is a little water (conc) The concentration of water will equalize on both sides but there will be more water molecules on one side
A simple rule to remember. SALT SUCKS!!!! Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty
Types of Solutions When you put a plant or animal cell into a liquid containing water, one of three things will happen 1. Cell will swell 2. Cell will stay the same size 3. Cell will shrink
ISOTONIC A cell in an isotonic solution has the same concentration in its cytoplasm as its surrounding environment Water will move through the plasma membrane but it enters AND leaves at the same rate "ISO" means the same
HYPOTONIC If the solution has a lower concentration of substances than inside the cell the solution is hypotonic More salt inside, more water outside. Since salt sucks, water will move into the cell. Water from high water to low water conc. The cell will gain water and grow larger. Swell
HYPTERTONIC If the solution has a higher concentration of substances than inside the cell the solution is hypertonic More salt outside, more water inside. Since salt sucks, water will move out of the cell. Water from high water to low water conc. The cell will lose water and shrivel. SHRINK Hyper kids go OUT to play
PASSIVE TRANSPORT: FACILITATED DIFFUSION Facilitated Diffusion moves molecules that cannot readily diffuse through cell membrane even though there is a concentration gradient Still moving from high to low Movement is assisted by carrier proteins Does not require energy
Hypotonic In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from bursting
Hypotonic In animal cells (& other cells), the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES will pump water out of the cell to prevent this.
This is why it is dangerous to drink sea water - its a myth that drinking sea water will cause you to go insane, but people marooned at sea will speed up dehydration (and death) by drinking sea water. This is also why "salting fields" was a common tactic during war, it would kill the crops in the field, thus causing food shortages.