The document discusses the structure and function of the plasma membrane and the movement of substances across it. The plasma membrane is a selectively permeable phospholipid bilayer that controls the movement of substances into and out of cells. Substances can move passively via simple diffusion, facilitated diffusion, or osmosis. Active transport requires energy and transports substances against a concentration gradient using carrier proteins.

1. movement of substances across the plasma membrane

2. what are the substances needed by the cells? how the needed substances move into the cells?

3. Substances needed by the cells Water Oxygen Nutrient Glucose Amino acid Mineral Fatty acid Vitamin The substances have to move across the membrane

4. Substances to be eliminate from the cells Carbon dioxide Urea Toxin

5. plasma membrane structure

6. Fluid Mosaic Model 1972 - Singer and Nicolson called the membrane a “Fluid Mosaic Model”. Mosaic: different proteins embedded in the phospholipids. Fluid: proteins and phospholipids can move freely in the membrane.

10. Components of a phospholipid bilayer. 1. phospholipids 2. proteins - enzymes, receptors, transport. 3. glycolipids 4. glycoproteins 5. carbohydrates 6. cholesterol

11. Plasma Membrane Boundary that separates the living cell from it’s non-living surroundings. Phospholipid bilayer Amphipathic - having both: hydrophilic heads hydrophobic tails ~8 nm thick Phospholipid

15. Controls traffic into and out of the cell with phospholipids and transport proteins . Selectively permeable >>> semi-permeable function Transport protein

16. What is Selective Permeability? The property of biological membranes which allows some substances to cross more easily than others.

17. Transport Proteins Transports molecules or ions across biological membranes Two types: Carrier proteins Pore proteins

18. Through phospholipids layer: Non polar molecules = Oxygen. Carbon dioxide, water , lipid soluble molecules By pore – proteins : water soluble molecules and ions By carrier- proteins and energy : ions. By carrier- proteins : glucose, amino acids.

19. Passive transport: NO energy is expended. Simple diffusion – gases, Osmosis – water facilitated diffusion : type of passive transport which uses transport proteins. – glucose and amino acid Active transport : Using carrier protein and energy – ions Movement of substances

20. Diffusion The net movement of a substance (molecules) down a concentration gradient from an area of high con centration to an area of low concentration .

23. Example:

26. Facilitated diffusion Allows diffusion of large, membrane insoluble compounds such as sugars and amino acids Does not require energy (passive) Highly Selective Substance binds to transport protein Fully reversible - molecules may enter the cell and leave the cell through the transport protein. Particles move from areas of high concentration to areas of low concentration. Movement rate of particles will saturate Maximum rate limited by number of transporters Once all transporters are operating at 100%, an increase in concentration will not increase rate

29. Active Transport Movement across membrane with an energy cost (usually against concentration Used to pump specific compounds in or out of the cell Requires energy to overcome the concentration gradient or to allow a large or charged particle to cross membrane Requires specific carrier proteins The energy requirement distinguishes active transport from facilitated diffusion

32. Osmosis The movement of water across selectively permeable membranes . The water moves from a low concentration area to high concentration area

37. Cell membranes are completely permeable to water, therefore, the environment the cell is exposed to can have a dramatic effect on the cell.

40. Hypotonic solution Less solute More water Compare to cytoplasm of the cell

41. Hypertonic solution More solute Less water Compare to cytoplasm of the cell

42. Isotonic solution Equal concentration compare to cytoplasm of the cell

43. Hypertonic Solution : Solute concentration of solution higher than cell More dissolved particles outside of cell than inside of cell Hyper = more (think hyperactive); Tonic = dissolved particles Water moves out of cell into solution Cell shrinks

44. Hypotonic Solution : Solute concentration of solution lower than cell Less dissolved particles outside of cell than inside of cell Hypo = less, under (think hypodermic, hypothermia); Tonic = dissolved particles Water moves into cell from solution Cell expands (and may burst)

45. Isotonic Solution : Solute concentration of solution equal to that of cell No net water movement

52. application of osmosis Why the use of excess fertilizer caused wilting in plant?

53. Explain these preservation process