Movement of Molecules through a Cell Membrane

1. Movement of Molecules through a Cell Membrane

2. What happened when the air freshener was sprayed into the air near the door? The molecules moved throughout the classroom until everyone in the room was able to detect the odor. Diffusion – the movement of molecules from an area of high concentration [ ], to an area of lower concentration. Animation High Concentration [Low]

3. Eventually, the air freshener particles will be spread out evenly throughout the room (until they reach a point called EQUILIBRIUM)

4. [high] [low] Potassium Permanganate crystals in a dish of water • Molecules move out from the center [high] to the outside of the Petri dish [Low] until it is evenly distributed throughout the dish EQUILIBRIUM

5. Passive transport • When molecules move from an area of [high] to an area of [Low], they move with the concentration gradient • No energy is need – like riding your bike downhill.

6. Active transport • When molecules move from an area of [low] to an area of [high], they move against the concentration gradient. • Energy is need – riding your bike back up the hill

7. [High] Concentration gradient [low]

8. Diffusion Animation • Diffusion across a (cell) membrane occurs if the membrane is selectively permeable (some things can diffuse, others can’t. This is determined by the size of the molecule and the pore.

9. Impermeable membrane – no diffusion occurring Selectively permeable membrane – diffusion occurring

10. Osmosis demonstration of osmosis • Movement of water molecules through a selectively permeable membrane. Regulated by Osmotic Pressure • Animation

11. Hypertonic Solution Hypertonic – higher solute concentration in the solution than inside the cell - Cell will lose water and shrink up - Plasmolysis Putting salt on a slug or when you drink high sugar foods and get very thirsty.

12. Elodea Plasmolysis* -  loss of cytoplasmic structure due to water.

14. Hypotonic Solution Hypotonic solution – lower solute concentration in the solution than inside the cell Cell will swell up due to water coming into the cell Cytolysis – bursting of cells. Cell expands Turgor in plants (keeps cell wall pushed out and plant from wilting) Putting wilted veggies into fresh water

15. Hypotonic

17. Isotonic Solution: • same concentration of solutes in the cell as outside the cell • No net water movement • Most cells exists in an isotonic external environment

19. Turgor Pressure Plasmyolysis

20. Quiz Facilitated Diffusion • Movement of molecules across a membrane but with the assistance of a carrier protein • No energy is needed • Typically occurs with Glucose that can’t diffuse fast enough • Substances move quicker than by normal diffusion • Like a people mover at an airport. Same amount of work but done faster Animation

21. Active Transport – Movement of molecules from [Low] to [High]. • Energy is needed • Sodium – Potassium pump • Carrier Proteins become cell membrane pumps • Iodine, Calcium, Sodium, Potassium, Chlorine ions

22. Endocytosis and Exocytosis Engulfing of macromolecules & food particles into the cell membrane Animation1 Animation 2

23. Endocytosis – Cells ingest macromolecules & small organisms such as bacteria, paramecium, yeast cells. • Cell membrane surrounds material into a pouch. • Cell membrane around pouch pinches together to form a vacuole. • Vacuole may fuse with lysosome for digestion

24. 2 Types of Endocytosis • Pinocytosis (cell drinking) if solutes or fluids are involved • Phagocytosis (cell eating) if large particles or whole cells are involved Another animation Occurs with bacteria, viruses or phagocytes (WBC)

25. Exocytosis • – Release of vacuoles thru cell membrane. • May be proteins, waste materials, or indigestibles. • Vacuole fuses with membrane, release contents into environment • Animation