2.  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.  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.  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.  What structure maintains homeostasis in our cells?  How does it maintain homeostasis?  How? The Cell Membrane 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 is:  A phospholipid bilayer  Two layers made of proteins and lipids Phospholipid Structure:  Polar Head (hydrophilic—”water loving”)  Nonpolar Tails—(hydrophobic—”water fearing”) Draw:

7.  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 phospholipid bilayer › helps keep the membrane fluid

9.  Bilayer arrangement  Draw:

10.  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)

11. 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

12. 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

13.  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)

14. 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

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

16.  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

17.  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)

18. 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

19.  This represents a selectively permeable membrane.  It allows (selects) certain things to pass through it.  Is the membrane permeable to ?

20.  Molecules pass through the cell membrane in one of two general ways: › Passive Transport  Diffusion  Facilitated Diffusion  Osmosis › Active Transport  Vesicles  Pumps

21.  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 H 2 0 › 1 grain of salt has 120,000,000,000,000,000 molecules of salt

22.  Concentration Gradient- an area of high concentration next to an area of low concentration Low Concentration of Molecules High Concentration of Molecules

23.  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.

24.  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

25.  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

26. Air Freshener Diffusion in a Classroom

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

29. This process is called… diffusion

31.  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

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

33.  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

34. 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)

35.  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

36.  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)

38. Semi-

39. Click to open web page with interactive animation

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

41. http://sites.sinauer.com/cooper5e/animation0202. html

42.  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)

43. 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)

44. 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

45. 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

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

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

48. 10% salt 90% water Where is the greatest concentration of solvent? In the bag selectively permeable membrane Which way does the water move? Out of the bag What type of solution is this? Hypertonic

49. What happens to the bag? selectively permeable membrane 90 % solvent 10% salt

50. What happens to the bag? selectively permeable membrane 90 % solvent 10% salt

51. What happens to the bag? selectively permeable membrane 90 % solvent 10% salt

52. What happens to the bag? The bag shrinks. selectively permeable membrane 90 % solvent 10% salt

54.  Passive transport: › requires no energy › moves from high concentrations to low concentrations › Moves down the concentration gradient › Includes diffusion, facilitated diffusion and osmosis

55.  When molecules are moved from a low concentration to a high concentration they must use active transport › Cells must transport certain amino acids, sugars, etc. into their cytoplasm from the surrounding fluid. › Some of these substances, however, are already in higher concentrations inside versus outside.  Forcing molecules to move against their concentration gradient requires energy (ATP!)

56.  Vesicles can transport molecules across the cell membrane through: › Endocytosis- moving INTO the cell › Exocytosis- moving OUT of the cell  Requires energy

57.  Exocytosis can help get rid of wastes or secrete products like hormones or insulin  Requires energy

59. Pinocytosis (drinking)Phagocytosis (eating)

60.  Pumps force molecules to travel against their concentration gradient  For example, the sodium/potassium pump actively transports sodium molecules and potassium molecules through the cell membrane  Requires energy

61. http://www.goldiesroom.org/Note%20Packets/06%20Transport/00%20Transport--WHOLE.htm

62.  Na + pumped out of a cell  K + pumped into a cell  Important because it prevents cells from bursting by lowering the sodium inside causing less water to enter through osmosis.  Requires energy

63. Sodium Potassium Pump

65.  Cell transport involves proteins that require ATP for energy  These carrier proteins change shape to move molecules across the membrane  Another important way to move glucose into the cell uses transport proteins combined with an ion pump, this is called coupled transport

66.  Opposite of Passive Transport  Molecules go against the concentration gradient  Energy is provided by the ATP made in the mitochondria  Active transport can involve pumps or vesicles  Requires energy

67. http://www.goldiesroom.org/Note%20Packets/06%20Transport/00%20Transport--WHOLE.htm

71. http://www.wiley.com/legacy/college/boyer/0470003790/animations/membra ne_transport/membrane_transport.htm

72. 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

73.  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

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

76.  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

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

78. Click to open web page with interactive animation

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

80. http://sites.sinauer.com/cooper5e/animation0202. html

82. http://www.goldiesroom.org/Note%20Packets/06%20Transport/00%20Transport--WHOLE.htm

83. Sodium Potassium Pump

85. Pinocytosis (drinking)Phagocytosis (eating)

86. http://www.goldiesroom.org/Note%20Packets/06%20Transport/00%20Transport--WHOLE.htm