1. HOMEOSTASIS and the PLASMA MEMBRANE
Chapter 7-3

2. Maintaining a Balance
All organisms are subject to changes in their environment; temperature, pressure, gas levels, sunlight, chemicals, etc.

3. Cells must be able to control what enters and what leaves while at the same time maintaining concentrations of water, salts, glucose, etc. as they eliminate wastes and other unnecessary materials.

4. STRUCTURE of the PLASMA MEMBRANE
The plasma membrane – which is “selectively permeable” – is responsible for this regulation.

6. 2 layers of phospholipids (phosphate heads with lipid tails)
Plasma Membrane
2 layers of phospholipids (phosphate heads with lipid tails)

7. “hydrophilic” heads facing watery environments
“hydrophobic” tails facing away from the watery environments
“hydrophilic” heads facing watery environments

8. The lipid layer is periodically embedded with two kinds of proteins:
integral proteins
peripheral proteins

10. Integral Proteins
Proteins that span the width of the cell membrane – from surface to surface act as channels to help ferry non-lipid soluble materials into the cell (glucose, amino acids, large molecules, etc.)

12. Proteins that are on one surface of the membrane only
Peripheral Proteins
Proteins that are on one surface of the membrane only
act as markers (“flags”) or as docking sites for other chemicals such as hormones and enzymes.

14. Fluid-Mosaic Model
Because the lipids are not bound together, they can move side-to-side in a fluid fashion.

15. peripheral protein
integral protein
peripheral protein

16. Cellular Transport

17. Molecules are constantly in motion and are always colliding with each other.

18. Movement of Materials Through a Cell Membrane
Passive Transport
Active Transport

19. PASSIVE TRANSPORT
Does NOT require energy from the cell - from HIGH to LOW concentration

20. Active Transport
A process that requires energy that enables material to move across the cell membrane AGAINST a concentration gradient

21. Passive Transport Diffusion:
Diffusion Simulation

22. The process by which molecules of a substance move from areas of high concentration to areas of low concentration.

24. Diffusion Gizmo | ExploreLearning

25. Osmosis
Diffusion of water molecules through a selectively permeable membrane.

27. The diffusion of water molecules.
OSMOSIS
The diffusion of water molecules.
Diffusion across a membrane (osmosis)

28. Effects of Osmosis on Cells
Isotonic – concentration of solutes is the SAME inside and outside cell membrane

30. Effects of Osmosis on Cells
Hypertonic – solution has HIGHER solute concentration than the cell

32. Effects of Osmosis on Cells
Hypotonic – solution has a LOWER solute concentration than the cell

34. Hypertonic, Hypotonic, Isotonic
Passive Transport

35. Facilitated diffusion
Movement of specific molecules through a cell membrane through protein channels

37. ACTIVE TRANSPORT
Requires ENERGY by the cell. From LOW to HIGH concentration

38. Individual molecules are carried through the membranes via proteins in the cell membrane.

39. Active transport

41. Endocytosis (Type 1)
the process of taking the material INTO the cell by infoldings of the cell membrane.

43. Two Types:
Phagocytosis: engulfing of large particles into the cell.

44. Two Types:
Pinocytosis: cell takes in fluid from the surrounding environment

45. Types of Endocytosis with sound

46. Exocytosis (Type 2)
Molecules are taken up by the cell forming pockets along the membranes to REMOVE molecules from the cell.

47. Exocytosis

49. Quiz

50. If you start with A, do you end up with B or C?

51. 1. Define diffusion.
2. Define osmosis.
3. Define active transport.
4. What is endocytosis and exocytosis?