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Cell Transport

Cell Transport. Homeostasis Cell Membrane Vocabulary Diffusion and Osmosis Active vs. Passive Transport. Homeostasis. Homeostasis means maintaining a balance internally (inside a cell or organism) despite what is going on externally (outside the cell or organism).

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Cell Transport

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  1. Cell Transport Homeostasis Cell Membrane Vocabulary Diffusion and Osmosis Active vs. Passive Transport

  2. Homeostasis • Homeostasis means maintaining a balance internally (inside a cell or organism) despite what is going on externally (outside the cell or organism). • Organisms must adjust to changes in the environment in order to survive or they could die!

  3. Homeostasis • For example, when you need to drink water, your brain tells your kidneys to use less water in making urine so you can keep your blood flowing nicely (and then your brain tells you that you’re thirsty!)

  4. Homeostasis • Another example, if it is below freezing outside, you must put on a heavy coat, gloves, double socks, a warm hat, ear muffs, and lots and lots of layers to maintain a healthy INTERNAL body temperature despite the EXTERNAL temperature

  5. Homeostasis The Cell Membrane • What structure maintains homeostasis in our cells? • How does it maintain homeostasis? • How? By controlling the passage of molecules, such as water, salts (ions), amino acids, carbohydrates, etc in and out of the cell. (it regulates what enters and leaves) -through passive transport, & active transport -cell to cell communication!

  6. The Cell Membrane The Cell Membrane is: • A phospholipidbilayer • Two layers made of proteins and lipids Phospholipid Structure: • Polar Head (hydrophilic—”water loving”) • Nonpolar Tails—(hydrophobic—”water fearing”) Draw:

  7. The Cell Membrane • proteins embedded in the phospholipid layers • some go all the way through both layers (integral) • some are just on the inside of the membrane or just on the outside of the membrane (peripheral) • cholesterol is a second lipid that’s also found inbedded in the phospholipidbilayer • helps keep the membrane fluid

  8. The Cell Membrane • Bilayer arrangement • Draw:

  9. The Cell Membrane • There are 3 types of membrane proteins imbedded or “floating” in the lipid bilayer, each with a different function: • transport—help molecules enter or leave the cell • marker—identify the cell • receptor—allow cells to communicate (send and receive messages)

  10. The Cell Membrane 1. Transport Proteins • function as “gates/passageway” • allow sugars, salts (ions), amino acids and carbohydrates to cross the membrane • channel proteins • gated ion channels—gates that open/close in response to charged particles • these are important in nerve cell function, but we will not study them in detail • carrier proteins—change shape to allow specific molecule to pass through the membrane when it binds to the carrier protein; some require energy (ATP), others do not require energy • carrier proteins are important in getting glucose into the cells http://personal.tmlp.com/Jimr57/textbook/chapter3/cms2.htm

  11. The Cell Membrane Marker Proteins • Cell’s “Name Tag” • Protein sticks out of phospholipid layer • Often has carbohydrates attached to outside end • Functions in cell identification to identify the cell to other cells and molecules • Important in • immunity—so various white blood cells in your body do not mistake your cells for foreign cells - blood typing – so you can’t receive just any ol’ type of blood

  12. Blood Typing Continued • each blood type is based on the glycoproteins (protein-carbohydrate molecule) that stick up from the cell membrane. • type A – has a glycoprotein named antigen A • type B – has a glycoprotein named antigen B • type AB – has both antigen A and antigen B • type O – has no marker proteins (no glycoproteins/antigens)

  13. The Cell Membrane Receptor Proteins- primary molecules involved in cell communication • Function as messengers • Receive information from the environment (extracellular fluid, blood, interstitial fluid) and transmit that info to the inside of the cell • Protein has specific shape/charge to only allow certain molecules (like hormones) to bond • Triggers a response in cell http://personal.tmlp.com/Jimr57/textbook/chapter3/cms2.htm

  14. http://www.d.umn.edu/~sdowning/Membranes/signalinganim.html Click, hold, and drag slider to move forward, bckword, or slow down

  15. Cell Membrane • in step 1 a signal molecule (sometimes called a ligand) binds to a receptor protein in the cell membrane • examples of signal molecules include insulin and testosterone • in step 2 the receptor protein has changed shape as a result of the signal molecule binding, which can cause additional changes or reactions inside the cell • after step 2, there are 2 possibilities: • step 3 says “cellular response” – an example of a cellular response is an enzyme being activated to make a reaction happen • for example, insulin binding to a receptor in a liver or muscle cell membrane would tell the cell to start hooking together glucose into glycogen for storage • step 4 says “change in gene expression” – this means that a gene in the DNA is going to be “read” and mRNA made (transcription will occur); this will ultimately result in the cell producing a particular protein • for example, testosterone binding to a receptor protein in a skin cell could tell the cell to begin producing hair and a male would then begin growing a beard

  16. Cell Membrane • it’s important to note that the binding of the signal molecule (like insulin or testosterone) to the receptor is temporary; when it unbinds, the signal stops and the cell response (enzyme reaction or gene expression) stops; this is another way organisms maintain homeostasis (you don’t always want to store sugar, sometimes you want to break it down, so insulin is not always bound to your cells but is only released into the blood from the pancreas when blood sugar levels are high; when they’re low, another molecule called glucagon is released and would tell the cells to break down glycogen and release the glucose)

  17. The Cell Membrane The Cell Membrane is: • Selectively permeable/semipermeable • permeable means particles, like molecules, can travel through • selectively or semi permeable means it only allows SOME things through and not others

  18. The Cell Membrane • This represents a selectively permeable membrane. • It allows (selects) certain things to pass through it. • Is the membrane permeable to ? • Is the membrane permeable to ?

  19. The Cell Membrane • Molecules pass through the cell membrane in one of two general ways: • Passive Transport • Diffusion • Facilitated Diffusion • Osmosis • Active Transport • Vesicles • Pumps

  20. Cell Transport Vocabulary • Molecule- the smallest unit of a compound/substance • Cannot be seen with the naked eye • 1 drop of water has 16,700,000,000,000,000,000,000 molecules of H20 • 1 grain of salt has 120,000,000,000,000,000 molecules of salt

  21. Cell Transport Vocabulary • Concentration Gradient- an area of high concentration next to an area of low concentration High Concentration of Molecules Low Concentration of Molecules

  22. Cell Transport Vocabulary • Equilibrium is when there is an EQUAL amount of molecules on each side of the membrane • There is no net movement of molecules (you won’t SEE a change) but there is continuous movement of molecules back and forth through the membrane.

  23. Passive Transport • Passive Transport is when molecules move from an area of HIGH concentration to an area of LOW concentration until equilibrium is reached. • Requires NO ENERGY! • Examples: • Diffusion • Osmosis • Facilitated Diffusion

  24. Passive Transport • Diffusion- the process by which molecules (“stuff”) spread from areas of high concentration, to areas of low concentration • Molecules are said to go “down” or “with” the concentration gradient. • Requires no energy

  25. Air Freshener Diffusion in a Classroom

  26. Where is the least concentration of cows? Where is the greatest concentration of cows? What will happen when the gate is opened?

  27. This process is called… diffusion

  28. Passive Transport • Facilitated Diffusion • What does facilitate mean? • When substances move from high to low concentration (down the concentration gradient) using channel/carrier proteins located in membrane • Does not require energy

  29. Facilitated Diffusion Animation http://www.d.umn.edu/~sdowning/Membranes/diffusionanimation.html Click, hold, and drag slider to move forward, bckword, or slow down

  30. Passive Transport • Osmosis- a special type of diffusion • the process by which WATER molecules move from an area with a high concentration of water to an area of low concentration of water across a membrane • the “diffusion of water” • Requires no energy

  31. Passive Transport Osmosis- • may be the passing of water through pores • (spaces between the molecules of) in the membrane • -may be the passing of water through special • channel proteins called aquaporins (2003 Nobel Prize • to Agre & McKinnon for this discovery)

  32. Osmosis • in biological systems, water is often the only substance that can pass through a membrane • water moves INTO a solution with a HIGHER concentration of SOLUTE (molecules/particles) • water moves OUT OF a solution with a LOWER concentration of SOLUTE

  33. Passive Transport • water will move in where there is a low concentration of SOLVENT (water), and a high concentration of SOLUTE (water) • A solute = “stuff” (ions, glucose) • A solvent = “water” (you’ll learn about different solvents in chemistry, but in biology the solvent is almost always water)

  34. Osmosis Semi-

  35. Click to open web page with interactive animation

  36. How osmosis works (click here or picture to go to video)

  37. Passive Transport Animation http://sites.sinauer.com/cooper5e/animation0202.html

  38. Passive Transport • There are three words use to compare and describe solutions: • Hypotonic- water moves INTO a cell and the cell swells (gets bigger) • Hypertonic – water moves OUT of a cell and the cell shrinks (gets smaller) • Isotonic- water moves into AND out of a cell at an equal rate (remember- molecules are constantly moving)

  39. Passive Transport Hypotonic- • describes a solution that is less CONCENTRATED (has less solute, more water) • when a cell is placed in a hypotonic solution, the cell will swell as water moves INTO the cell • there is more solvent/less solute on the outside of the cell than the inside • the solvent (water) moves to an area of low solvent (water) concentration • the cell could burst (lyse)

  40. Passive Transport Hypertonic- • describes a solution that is more CONCENTRATED (has more solute, less water) • when a cell is placed in a hypertonic solution, water moves OUT of a cell and the cell shrinks(gets smaller) • there is less solvent/more solute on the outside of the cell than the outside • the solvent (water) moves to an area of low solvent (water) concentration

  41. Passive Transport Isotonic: • describes a solution that is of equal concentration to another • water moves into AND out of a cell at an equal rate (remember- molecules are constantly moving) • No change in the size of the cell will be observed • the concentration of solvent and solute on the inside of the cell is equal to the concentration of solvent and solute on the outside of the cell

  42. Practice • Draw arrows to show the flow of water • Label at the top if the solution is isotonic, hypotonic or hypertonic

  43. Where is the greatest concentration of solvent? Outside of the bag Which way does the water move? Into the Bag What type of solution is this? 100% distilled water Hypotonic selectively permeable membrane

  44. 90% water 10% salt Where is the greatest concentration of solvent? In the bag Which way does the water move? Out of the bag What type of solution is this? 80% distilled water Hypertonic selectively permeable membrane

  45. What happens to the bag? 90 % solvent 10% salt 80% distilled water selectively permeable membrane

  46. What happens to the bag? 90 % solvent 10% salt 80% distilled water selectively permeable membrane

  47. What happens to the bag? 90 % solvent 10% salt 80% distilled water selectively permeable membrane

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