Cell Membrane & Cell Transport

1. Cell Membrane & Cell Transport

2. Cell Membrane Cell Wall Cell membrane Cell membrane vs. cell wall All cells have cell membranes Flexible barrier Function: maintain homeostasis within the cell

3. protein channel Layer 1 Cell Membrane Layer 2 lipid bilayer protein pump Cell membrane structure • Many names… cell membrane, plasma membrane, phospholipid bilayer • Phospholipid bilayer – two layers of phospholipids with embedded proteins

4. Cell membrane structure Hydrophilic head – “water loving” attracts water Hydrophobic tail – “water fearing” repels water Creates a constant push and pull Phosopholipid Bilayer

5. Cell membrane structure Small materials can pass easily: Push and pull of water Porous nature Vibrating phospholipids, creating openings Phosopholipid Bilayer

6. Cell membrane structure “Fluid Mosaic Model”: explains the structure of the cell membrane Proteins and other embedded materials “float” within the cell membrane

7. Cell membrane structure Carbohydrate Chain Cholesterol Phospholipid Bilayer Membrane Protein Transport/Channel Proteins

8. Cell membrane Function • “Gatekeeper” • Semipermeable : Allows certain materials in and out of the cell • Nutrients IN • Waste OUT • CELL TRANSPORT: MOVEMENT OF MATERIALS IN AND OUT OF CELLS

9. Cell transport • The movement of materials in and out of cells (cell transport) … can be passive or active • Passive Transport: Does NOT require energy • Active Transport: Requires energy

10. Cell transport • Passive Transport • Does NOT require energy • Movement of materials from HIGH  LOW • “with the concentration gradient” • Diffusion, Osmosis, Facilitated Diffusion

11. Cell transport • Active Transport • REQUIRES the use of energy • Movement of materials from LOW  HIGH • “against the concentration gradient” • Endocytosis and Exocytosis

12. Passive Transport - diffusion Diffusion: movement of small particles from high to low until equilibrium is reached

13. Passive Transport - diffusion Diffusion: movement of small particles from high to low until equilibrium is reached Particles are small enough to pass through the porous cell membrane

14. Passive Transport - OSMOSIS Osmosis: the diffusion of water across a selectively permeable membrane Outside Cell Water will travel from HIGH concentration  LOW concentration Inside Cell

15. Passive Transport - OSMOSIS Osmosis: the diffusion of water across a membrane Water travels from high  low Osmosis will take place until equilibriumis reached 25% sugar 75% water 60% sugar 40% water 50% sugar 50% water 50% sugar 50% water

16. Passive Transport - OSMOSIS Osmosis: the diffusion of water across a membrane Water will move in and out of cells when they are placed in various solutions

17. Passive Transport - OSMOSIS Isotonic Solution – equal amount of solute in and out of cell. Water moves in and out of cell in equal amounts Cell size does not change

18. Passive Transport - OSMOSIS Hypertonic Solution – higher concentration of solute outside cell. Water diffuses out of cell through osmosis. Cell shrinks/shrivels in size.

19. Passive Transport - OSMOSIS Hypotonic Solution – higher concentration of solute inside cell. Water diffuses into cell through osmosis. Cell expands and can even burst.

20. Glucose molecules outside of cell inside of cell Passive Transport – facilitated diffusion Facilitated Diffusion – Diffusion of larger molecules which must be “helped” through the membrane by traveling through channel proteins & carrier proteins High  Low! No energy!

21. Outside cell Inside cell squeezing motion “bridge”

22. Active Transport review • Active Transport • REQUIRES the use of energy • Movement of materials from LOW  HIGH • “against the concentration gradient” • Endocytosis and Exocytosis

23. Active Transport - endocytosis Endocytosis – the movement of large molecules INTO the cell Low  High Requires energy

24. Active Transport - endocytosis Molecule “bumps” into cell membrane Cell membrane wraps around and engulfs particle Creates a temporary vesicle/vacuole for transport

25. Active Transport - endocytosis • Examples: • Your white blood cells use energy to engulf bacteria • An amoeba bumps into something tasty!

26. A white blood cell chasing a bacterium https://www.youtube.com/watch?v=JnlULOjUhSQ

27. Active Transport - exocytosis Exocytosis – the movement of large molecules OUT OF the cell Low  High Requires energy

28. Active Transport - exocytosis The golgi body plays a major role in the secretion (release) of proteins and other materials through exocytosis