In This Lesson: Cell Membranes and Cell Transport (Lesson 3 of 5) Today is Friday (!),October 11th, 2013 Pre-Class: Today is our first look at the cell. First, choose one of the following to answer in your notes: What do the terms diffusion, osmosis, or passive/active transport mean to you? Have you ever had Aquafina or Dasani water? Why is it different from Poland Spring, for example? Do you know the name of the process? Also, take a worksheet from the turn-in box and get a paper towel for your pair.
Today’s • Cell membrane [Part 1] • Form • Brief aside on blood type • Cell transport [Part 2] • Function • Doodling on whiteboards • Yes, you will be making pictures. • Where is this in my book? • Academic: P. 182-189 • Honors: P. 79 and following… http://www.greatscopes.com/objectives.jpg
But First, a Word About Size… • Ye OldeBioScale • What It Looks Like • Scale of the Universe
Osmosis and DiffusionPre-Class • What did you come up with? • We will talk about the details of these processes today and later in the week. • One other thing… • When you hear me mention an organic molecule today, raise your hand. • Keep your ears open!
The Cell Membrane • Like the “shell” of the cell. • Also called the plasma membrane. • Double layer of phospholipids called a bilayer. • Separates the cell’s cytoplasm from the extra-cellular matrix. • ECM • Which one is outside, which is inside? http://api.ning.com/files/bjQpqLaT64H6U9Rm1cTtQzE8e7iMnMN*e7NCiUPA*ly2QfxrMD-yIx3-4bZ494uPFWMBd4jtn3cnGophzG2Rj1i*8RZJLtZh/et2.jpg
Permeability • Some things are “impermeable:” • Raincoats, balloons, brick walls. • Some things are “permeable:” • Air, water. • Some things are “semi-permeable:” • Nets, gates, cell membranes. • Semi-permeability is sometimes called selective permeability.
The PhospholipidBilayer • Most plant and animal cells have a double-layered cell membrane called a phospholipidbilayer. • The phospholipidbilayer acts as its own gate. • Because the cell is in and made of water, a polar substance, the non-polar tails stay on the inside of the layer. • This polar/non-polar deal makes the phospholipidamphipathic. Polar -----------> Non-Polar Polar -----------> http://textbookofbacteriology.net/themicrobialworld/phospholipid_bilayer.jpg
P Phospholipids? • Fun fact: A phospholipid is actually just like a triglyceride molecule… • …but it’s usually unsaturated… • …missing a fatty acid chain (diglyceride)… • …and with a phosphate group. Glycerol Molecule Fatty Acid Chains http://bioweb.wku.edu/courses/biol115/wyatt/biochem/lipid/P-lipid.gif
What It Looks Like http://micro.magnet.fsu.edu/cells/plasmamembrane/images/plasmamembranefigure1.jpg
Modeling the Cell Membrane • Time for a class bonding experience. • The Classroom Cell! • So to summarize, you are a phospholipid. • You have a polar [hydrophilic] “head” (your upper body) and a non-polar [hydrophobic] “tail” (your legs). • The desks are like the imaginary dividing line between polar and non-polar. Polar Non-Polar Non-Polar Polar http://textbookofbacteriology.net/themicrobialworld/phospholipid_bilayer.jpg http://farm1.static.flickr.com/76/174946884_64a0b8b304.jpg
Now for the Proteins • Membrane proteins are embedded in some places in the cell membrane. They might have one of many jobs: • Marker Proteins • Receptor Proteins • Enzymes • Transport Proteins http://library.thinkquest.org/C004535/media/cell_membrane.gif
And we return to the model… • More “Classroom Cell!” Embedded Protein!
There’s more… • Attached to some proteins are carbohydrates (remember them?) that help in cell-cell recognition.
And we return to the model one last time… • More “Classroom Cell!”
Okay, one last thing… • Cell membranes are fluid. • What does this mean? • The cell’s phospholipids and embedded proteins flow around the membrane and are in motion. • Called the Fluid Mosaic Model. • A certain lipid (actually, a steroid) can slow down or stop this fluidity. • Do you know what it is? http://www.herdaily.com/blogimg/health/c----.bmp
Fluid Mosaic Model • Remember, it moves!
Challenge Question • We know that carbohydrates are attached to proteins in the cell membrane so that other cells can identify them. • What do you think might happen if a cell lost its carbohydrate receptors in your body?
Blood Type • For a look at how important these small signal molecules are, we’ll look at blood type. • Anyone know their blood type in here? • We’re going to keep blood type simple for today, so let’s assume there are only four total blood types: • A, B, O, and AB.
Blood Type • Each red blood cell (except O) has a specific kind of receptor on it (in this case called an antigen). http://lomalindahealth.org/health-library/graphics/images/en/19450.jpg
White Blood Cells • You also have white blood cells (leukocytes) – they’re like angry policemen in your blood vessels. Receptor Receptor Receptor Receptor Receptor Receptor Receptor Receptor Receptor Receptor Receptor Receptor Receptor Receptor Receptor Receptor Receptor http://www.journaldunet.com/science/biologie/dossiers/07/immunite/lymphocyte.jpg
Blood Type • The wrong type of blood cell receptors causes agglutination (clumping) . • Example: My dad has Type A blood. If you give him Type B blood, the white blood cells will treat it as an invader. • Type O blood has no antigens so anyone can receive it. • More on blood when we get to the Genetics unit.
Micro Assignment • Tear a small piece of paper out of your notebook, write your name on it, and answer this question: • Which organic molecules play a role in the cell membrane? What roles do they play?
Molecular Transport [Part 2] Question: You have a sealed container holding one liter of pure oxygen (O2). You set the container on a table and leave it alone. After one week, are the oxygen molecules moving? Why or why not? http://www.electronichealing.co.uk/resources/Image/oxygen_drops.jpg
Molecular Movement • Molecules are always in motion. • Gas, liquid, and solid. • Molecules only stop moving at absolute zero. • So, even after a week (or two or three), the oxygen molecules would still be bouncing around.
Predictive Doodling • Today we’re going to do something I’m calling “Predictive Doodling.” • It’s like the Challenge Questions we do on the whiteboards, only you’ll be drawing instead of writing. • I’ll give you the “before,” you give me the “after.”
Before • Your whiteboard is a square container of water. • The dots are dissolved solutes. • What happens next? Talk to your partner – then draw it.
Diffusion Analogy • Imagine for a second that at the beginning of class I jammed all of you into the corner of the room. • Then, I just said, “Okay, relax,” and let you do what you wanted. • Would all of you stay put or would you spread out?
Note Organizer • Use this Cell Transport worksheet in place of your notebook for now…
Now let’s take a look atwhat the science says… • Diffusion is the passive “spreading out” of particles of a substance until the particles are spread out equally. • “Passive” meaning “no energy required.” • Diffusion is a form of passive transport. • Heat generally makes diffusion go faster. • Let’s try a little demo or two…
Diffusion Demos • Diffusion in Water • Diffusion in Air
Concentration Gradient • Concentration refers to the amount of a substance in a certain area. • Particles diffusedown their concentration gradient. • What does that mean? • In passive transport, particles always go from an area of high concentration to an area of low concentration.
Concentration Gradient High Warning: Steep Grade Low
Concentration Gradient High Concentration In Passive Transport, particles move from areas of high concentration to areas of low concentration. Substance Concentration Gradient Low Concentration
Predictive Doodling Again • The line in the middle is permeable to water, but not to solute. What happens next?
Osmosis • Osmosis is basically the same thing as diffusion, only with water molecules and some form of a barrier. • Osmosis is another form of passive transport. • Just like in diffusion, in osmosis, water moves from areas of high water concentration to low water concentration. • Or, water moves from areas of low solute concentration to areas of high soluteconcentration.
Osmosis • Which drink has more liquid in it? ICE ICE ICE ICE Drink A Drink B
Osmosis in a U-Tube Side A Side B Which side has more water on it? http://www.biologycorner.com/resources/osmosis.jpg
Osmosis in Carrots • Remember when I put the carrots in these beakers? • They were roughly equal carrots at the time. • For the carrot in the salt water, there is more solute outside the carrot than inside the carrot. • Which way does the water go? • What kind of change can we expect to find in the carrots?
Tonicity • Hypertonic solution • Relativelymore solute than surroundings. • Water flows TOWARD a hypertonic solution. • Hypotonic solution • Relatively less solute than surroundings. • Water flows AWAY FROM a hypotonic solution. • Isotonic solution • The same amount of solute as the surroundings. • No net water change.
Isotonic Solutions • Water does not experience a net movement in isotonic solutions. • There is no concentration gradient. Substance No concentration gradient No net movement of water
And now, I present to you… • …the key to EVERYTHING!!!!!!* • *osmosis-related. • Draw this in your notebook. Make it BIG. Hypotonic Hypertonic H2O Flow
What’s the connection? Blood hypertonic, surroundings hypotonic Isotonic solutions Blood hypotonic, surroundings hypertonic http://upload.wikimedia.org/wikipedia/commons/thumb/e/e3/Erythrozyten_und_Osmotischer_Druck.svg/450px-Erythrozyten_und_Osmotischer_Druck.svg.png
Osmosis Videos • Egg Osmosis • Onion Osmosis • Gummi Bear Osmosis
Osmosis in Plant Cells http://upload.wikimedia.org/wikipedia/commons/thumb/a/ab/Turgor_pressure_on_plant_cells_diagram.svg/2000px-Turgor_pressure_on_plant_cells_diagram.svg.png
Osmosis in Plant Cells • As we will soon learn, plant cells are good at holding water. • If they’re placed in a hypertonic solution, however, they lose water and wilt. • Their cells undergo plasmolysis. • Place them in a hypotonic solution and they will swell slightly, like a garden hose with water. • Their cells become turgid. • In animal cells, without a cell wall, the cell may burst in a process called cytolysis.
Osmosis in Kidneys http://classes.midlandstech.edu/carterp/Courses/bio211/chap25/Slide18.GIF
Osmosis in Kidneys • The proximal Loop of Henle is the part of the nephron (kidney component) responsible for re-absorbing water from urine. • With this in mind, would you guess that desert animals have larger or smaller Loops of Henle than other animals?
Osmosis in Kidneys http://www.answersingenesis.org/assets/images/articles/cm/v26/i3/rats.jpg
Osmosis in Merriam’s Kangaroo Rats http://www.bio.davidson.edu/Courses/anphys/1999/Chisholm/nephron1copy.wc2.jpg