2. The Cell Membrane and Homeostasis

3. Homeostasis Maintain an internal balance Cells keep the proper concentration of nutrients and water inside and push wastes outside.

4. Living Barrier The cell membrane is selectively permeable (or semi-permeable)  allows some things to pass through, while blocking others

5. Membrane Structure Lipid bilayer – two sheets of lipids (phospholipids).  Found around  The cell, the nucleus, vacuoles, mitochondria, and chloroplasts.  Embedded with proteins  Strengthened with cholesterol molecules.

6. What’s a Phospholipid? It’s a pair of fatty acid chains and a phosphate group.  Polar (water-loving) phosphate heads face out  nonpolar (water-hating) fatty acids hang inside.

9. Membrane Proteins Determine what particles can pass through the membrane (gates). Serve as enzymes (may speed reactions). Act as markers for recognition (the immune system).

11. Fluid Mosaic Model

12. Transport Across the Membrane

13. No Energy Passive transport – no energy is needed to move particles. Types  Diffusion  Facilitated Diffusion  Osmosis

14. Energy Active Transport – energy is required to move particles Types  Carrier Proteins  Endocytosis  Exocytosis