1. CELL MEMBRANE, DIFFUSION AND ACTIVE TRANSPORT

2. Cell Membranes are phospholipid bilayers, in fact all cellular membranes are phospholipid bilayers

4. Some substances are able to move through the cell membrane, others cannot

5. In part this is due to the phospholipid nature of the membrane.

6. The phosphate end of the molecule is hydrophilic and the lipid end is hydrophobic.

7. The phospholipid molecules naturally form a cell membrane.

9. Small molecules such as water can move between the phospholipid molecules into or out of the cell

10. Other molecules must be brought in or out of the cell by transmembrane proteins

11. Molecules can move through the cell membrane because of their kinetic molecular motion

12. Kinetic molecular motion is the movement of molecules because of temperature and molecular size. The higher the temperature the faster the movement.

13. Molecules move in a straight line until they hit another molecule.

14. Because of this random movement molecules travel farther in areas of low concentration and tend to spread out

15. This movement of molecules from areas of high concentration to areas of low concentration is called diffusion

16. If the molecule has enough energy it will pass through the fluid nature of the membrane’s phospholipids

17. If the molecule has enough energy it will pass through the fluid nature of the membrane’s phospholipids

18. Because not all molecules have enough energy to get through the cell membrane it is called a selectively permeable membrane

19. Molecules are moving in and out through the cell membrane because of molecular movement

20. Concentration is the comparison of the number of the solute to the number of molecules of the solvent.

22. If the blue circles represent water than water is the solvent

23. If the blue circles represent water than the yellow circles are the solute

24. Over time diffusion will cause the solutions on both sides of the membrane to have the same number of molecules. This condition is called equilibrium.

27. The greater the concentration gradient the more rapid the rate of diffusion

31. If sucrose cannot move through the membrane than the solution on the right has a higher concentration of water (100%)

32. The water will move from an area of high water concentration to an area of low water concentration

33. Water will move from an area of high water concentration to an area of low water concentration (if the solute cannot move through the membrane)

34. If there is a lower concentration of water in the cell than water will move into the cell

35. Until the concentration of water reaches equilibrium

37. Osmosis is the diffusion of water molecules

38. through a semi-permeable membrane

39. If the concentration of solute is the same inside the cell and outside the cell, the cell is said to be isotonic

41. If a cell is in a solution with a greater concentration than the cell, the solution is said to be hypertonic

42. If the concentration of the solute of the solution is greater than the concentration inside the cell, then the concentration of water in the solution is less than in the cell

43. If the solution outside the cell has a lower concentration than inside the cell, the solution is said to be hypotonic

44. If the concentration of the solution is hypotonic, then the solution has a greater concentration of water than in the cell.

46. Water will move into a cell in a hypotonic solution because the solution has a greater concentration of water.

47. Water will move out of the cell in a hypertonic solution, because the solution has a greater concentration of water than the cell

48. When water moves through a semi-permeable membrane into a cell, it increases the volume of the water

49. If a cell is in a hypotonic solution, it will swell

51. Diffusion of NaOH into an agar cube with phenophthalein

53. Rate = distance/time

54. Rate = distance/time
Distance = 0.2 cm = 2 mm

55. Rate = distance/time
Distance = 0.2 cm = 2 mm
Time = 12 minutes = 12minutes/60 minutes = 0.2 hr

56. Rate = distance/time
Distance = 0.2 cm = 2 mm
Time = 12 minutes = 12minutes/60 minutes = 0.2 hr
Rate = 2mm / 0.2hr = mm/hr

57. Volume of diffused area = Volume of entire cube – Volume of the cube without diffusion produces

58. Volume of diffused area = VD Volume of entire cube = VT Volume of cube without diffusion = VN

59. Volume of diffused area = VD

67. The cell phospholipid bilayer is selectively permeable.

68. Water, gases and some small organic molecules can move through the cell membrane because of molecular kinetic motion.

69. The Fluid-Mosaic Model of the cell membrane identifies the cell membrane as a selectively permeable membrane.

72. Imbedded in the membrane are channel proteins that funnel molecules through the membrane

73. The channel proteins provide a place for ions to go through the membrane because of the charge and kinetic molecular motion of the ion

74. Passive diffusion and Facilitated diffusion requires no use of energy on the part of the cell

76. Some transmembrane proteins require the use of ATP energy to pull certain molecules into the cell

82. Exocytosis-- Secretion from the cell by fusing the membrane of a vesicle with the cell membrane

83. Endocytosis Taking in a substance through the formation of a vesicle
Three types: Phagocytosis, Pinocytosis, Receptor-Mediated Endocytosis

84. Phagocytosis
Taking in a large food particle through the formation of a vesicle

85. Pinocytosis
Forming a vesicle around a liquid or a number of small particles

86. Receptor-Mediated Endocytosis
A form of pinocytosis which uses receptor proteins to bind the molecules first

87. The kidney is an organ made up of thousands of filters called nephrons

88. The filtering process begins when plasma is forced out of the blood in the network of small blood vessels called the glomerulus

89. The pressure of going from a wide artery to long, narrow capillaries forces water and small molecules through the cells into the glomerular capsule.

90. The water and small solutes then passes through the glomerulus of the tubules of the nephron

91. Because the loop of the nephron is longer in the kangaroo rat is able to absorb almost all the water in urine

92. As the liquid from the blood moves down the tubules water and important molecules are reabsorbed

93. The solution in the tubules is hypotonic, thus the water moves back into the blood by osmosis.

95. In the descending loop water diffuses out of the solution forced from the blood into the Bowman’s capsule.

97. Many large molecules, such as glucose, amino acids and hormones, are reabsorbed by active transport

98. In the proximal convoluted tubule salt is pumped back into the blood, making the blood hypertonic. The water moves by osmosis back into the blood.

99. Glucose and amino acids are returned to the blood by carrier proteins
Glucose and amino acids are returned to the blood by carrier proteins. If the blood is hypertonic for glucose, then the glucose remains in the urine.

102. Dialysis uses high pressure to force small molecules through the dialysis membrane.

103. Depending on the size of the holes in the membrane waste products can be forced out and then by making the holes smaller, smaller molecules can diffuse back into the blood.

104. The main difference between dialysis and kidney function is that the kidneys can remove molecules, such as potassium ions, from the blood and urine by active transport against the concentration gradient.