1. Cells and Homeostasis
There must be ways to transport materials into and out of the cell. Vital processes such as exchanging gases (usually CO2 and O2), taking in water, minerals, and food, and eliminating wastes require that molecules move through the membrane that surrounds the cell. This membrane is a complex structure that is a barrier separating the contents of the cell from its surroundings, for controlling the movement of materials into and out of the cell, and for interacting with the environment surrounding the cell.

2. Plasma (cell) membrane – the membrane at the boundary of every cell.
It is selectively permeable – meaning that it controls the substances entering and exiting the cell.

3. The plasma membrane is made up of a phospholipid bilayer.
The phospholipid bilayer is made up of single units called phospholipids.

4. A phospholipid is made up of:
A polar hydrophilic head (polar head - phosphate group and glycerol)
A non-polar hydrophobic tail
(2 chains of fatty acids)

6. The non-polar, hydrophobic tails position themselves in the middle region of the bilayer. The polar, hydrophilic heads positions facing outwards and interacts with the water.
OUTSIDE – EXTRACELLULAR MATRIX
PHOSPHOLIPID
BILAYER
INSIDE – CYTOPLASM

7. Fluid Mosaic Model
The fluid mosaic model describes the plasma membrane of animal cells, in which the membrane is a fluid structure with a “mosaic” of various proteins embedded or attached.

8. Integral proteins – are protein structures that completely spans the hydrophobic region of the plasma membrane.
Peripheral proteins – are protein structures that are attached to the surface of the plasma membrane and not embedded in the lipid bilayer.

10. This can be done in two ways:
Cells must maintain an internal balance of substances, and requires the ability to eliminate toxins and waste products produced within the cell.
This can be done in two ways:
Passive Transport
Active Transport

11. Passive Transport
Does not require energy for transport of materials into and out of the cell.
Examples:
Simple Diffusion
Osmosis
Facilitated diffusion

12. Solutes will move in the direction of higher concentration to lower concentration of a particular solute.
Bidirectional

14. Brownian motion – the random motion of molecules.
1:35 – 2:12

15. Simple Diffusion
Doesn’t require energy
Moves high to low concentration
Example: Oxygen diffusing into a cell and carbon dioxide diffusing out. 

16. Facilitated Diffusion
Doesn’t require energy
Uses transport proteins to move from high to low concentration
Examples: Glucose or amino acids moving from blood into a cell.

17. Osmosis - diffusion of water across the plasma membrane down its concentration gradient
Moves from HIGH water potential (low solute) to LOW water potential (high solute)

18. Diffusion of H2O Across A Membrane
The Plasma Membrane
2/16/2019
Diffusion of H2O Across A Membrane
High H2O potential Low solute concentration
Low H2O potential High solute concentration
G. Podgorski, Biol. 1010

19. Aquaporins Water Channels Protein pores used during OSMOSIS
The Plasma Membrane
2/16/2019
Aquaporins
Water Channels
Protein pores used during OSMOSIS
Speed up diffusion rate
WATER MOLECULES
G. Podgorski, Biol. 1010

20. Cell in Isotonic Solution
The Plasma Membrane
2/16/2019
Cell in Isotonic Solution
10% NaCL 90% H2O
ENVIRONMENT
CELL
NO NET MOVEMENT
10% NaCL
90% H2O
What is the direction of water movement?
equilibrium
The cell is at _______________.
G. Podgorski, Biol. 1010

21. Cell in Hypotonic Solution
The Plasma Membrane
2/16/2019
Cell in Hypotonic Solution
10% NaCL 90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water movement?
G. Podgorski, Biol. 1010

22. Cell in Hypertonic Solution
The Plasma Membrane
2/16/2019
Cell in Hypertonic Solution
15% NaCL 85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement?
G. Podgorski, Biol. 1010

23. Video

24. Cells in Solutions The Plasma Membrane 2/16/2019
G. Podgorski, Biol. 1010

25. NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
The Plasma Membrane
2/16/2019
Isotonic Solution
Hypotonic Solution
Hypertonic Solution
NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
CYTOLYSIS
PLASMOLYSIS
G. Podgorski, Biol. 1010

26. Cytolysis & Plasmolysis
The Plasma Membrane
2/16/2019
Cytolysis & Plasmolysis
Cytolysis
Plasmolysis
G. Podgorski, Biol. 1010

27. Osmosis in Red Blood Cells
The Plasma Membrane
2/16/2019
Osmosis in Red Blood Cells
Isotonic
Hypertonic
Hypotonic
G. Podgorski, Biol. 1010

28. What Happens to Blood Cells?

29. isotonic hypotonic hypertonic hypertonic isotonic hypotonic
The Plasma Membrane
2/16/2019
isotonic
hypotonic
hypertonic
hypertonic
isotonic
hypotonic
G. Podgorski, Biol. 1010

30. Active Transport Requires energy or ATP
Moves materials from LOW to HIGH concentration
AGAINST concentration gradient
Analogy of the bus for active transport
Ask students to think of their own analogy… think for a minute, then share with the class.

31. What is ATP?
Adenosine Triphosphate

32. Active transport
Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients.
Called Na+-K+ Pump

33. Sodium-Potassium Pump
3 Na+ pumped out for every 2 K+ pumped in; creates a membrane potential

34. Crash Course – In Da Club

35. Compare and Contrast
List as many things that are similar and as many things that are different about passive transport and active transport.

36. Quiz… Just for Fun  Question 1
In which type of transport are there carrier proteins?
Passive transport (facilitated diffusion, osmosis) and active transport

37. Quiz… Just for Fun  Question 2
Which type of transport is non-specific?
Simple diffusion

38. Quiz… Just for Fun  Question 3
Which type of transport works against the concentration gradient?
Active transport

39. Quiz… Just for Fun  Question 4
Which type(s) of transport is bilateral?
Passive transport

40. Quiz… Just for Fun  Question 5
Which type(s) of transport requires the use of energy in the form of ATP?
Active transport

41. Quiz… Just for Fun  Question 6
Which substances can cross the cell membrane through simple diffusion? Give examples.
Oxygen, carbon dioxide

42. Quiz… Just for Fun  Question 7
What does it mean by moving “down its concentration gradient”?
Moving from an area of high concentration to an area of low concentration

43. What is the net movement of water? Into the cell
= water molecule
hypotonic
hypertonic
What is the net movement of water?
Into the cell
What will happen to the cell as a result?
Burst - cytolysis

44. What is the net movement of water? Out of the cell
= water molecule
hypertonic
hypotonic
What is the net movement of water?
Out of the cell
What will happen to the cell as a result?
Shrivel - plasmolysis

45. What is the net movement of water? Equal movement into and out
= water molecule
isotonic
What is the net movement of water?
Equal movement into and out
What will happen to the cell as a result?
Cell is at equilibrium

46. What is the net movement of water? Out of the cell
= water molecule
= table salt molecule
hypertonic
hypotonic
What is the net movement of water?
Out of the cell
What will happen to the cell as a result?
Shrivel - plasmolysis

47. What is the net movement of water? Equal movement into and out
= water molecule
= table salt molecule
isotonic
What is the net movement of water?
Equal movement into and out
What will happen to the cell as a result?
Cell is at equilibrium

48. Movements of macromolecules, such as proteins are called bulk transport.
This occurs through either one of two processes called endocytosis or exocytosis.

49. Exocytosis Transport materials out of the cell.
Important for expulsion of waste materials and to secrete important macromolecules, such as, enzymes and hormones.
“exo” meaning exit

51. The Plasma Membrane
Exocytosis
2/16/2019
Exocytic vesicle immediately after fusion with plasma membrane.
G. Podgorski, Biol. 1010

52. Endocytosis Transport materials into the cell.
The opposite of exocytosis.
“endo” meaning enter

53. There are 3 types of endocytosis
Phagocytosis (cellular eating)
Pinocytosis (cellular drinking)
Receptor-mediated endocytosis
Pino = drink
Phago = eat

56. Endocytosis – Phagocytosis
The Plasma Membrane
2/16/2019
Endocytosis – Phagocytosis
Definition for pseudopodium
Used to engulf large particles such as food, bacteria, etc. into vesicles
Called “Cell Eating”
G. Podgorski, Biol. 1010

57. Pinocytosis Most common form of endocytosis.
The Plasma Membrane
Pinocytosis
2/16/2019
Most common form of endocytosis.
Takes in dissolved molecules as a vesicle.
G. Podgorski, Biol. 1010

58. Receptor-Mediated Endocytosis
The Plasma Membrane
2/16/2019
Receptor-Mediated Endocytosis
Some integral proteins have receptors on their surface to recognize, bind and take in hormones, cholesterol, etc.
G. Podgorski, Biol. 1010

60. Receptor-Mediated Endocytosis
The Plasma Membrane
Receptor-Mediated Endocytosis
2/16/2019
G. Podgorski, Biol. 1010

61. Animation

62. Receptor-mediated endocytosis
Receptors on the plasma membrane will only bind to specific molecules, called ligands, for ingestion.
Example: the uptake of cholesterol into the cell

63. PLEASE NOTE!
Both endocytosis and exocytosis processes require the use of energy in the form of ATP
Therefore, they are both forms of active transport

64. Quick Quiz
Question 1
What is the process by which materials are exported out of the cell?
Phagocytosis
Exocytosis
Endocytosis
Bulk transport

65. Quick Quiz
Question 2
Mammalian cells use _______ to import cholesterol.
Phagocytosis
Pinocytosis
Endocytosis
Receptor-mediated endocytosis

66. Quick Quiz
Question 3
Pinocytosis is the process of “cellular drinking”
True
False

67. Quick Quiz
Question 4
Phagosomes must fuse with lysosomes to digest imported materials.
True
False