1. Cell Membranes and Transport

2. A Cell is a Container A cell is the basic unit of life A cell and some organelles are containers formed by one or more membranes Membranes must be selectively permeable barriers to maintain specific internal conditions for life functions (homeostasis).

3. Phospholipid ← attracts water ← repels water

4. Phospholipids Form a Bilayer in Water

5. The Cell Membrane: Fluid Mosaic Model

6. Components of the Cell Membrane Phospholipid Bilayer: serves as a barrier separating water in (cytoplasm) from water out (extracellular fluid or environment) Cholesterol: stabilizes membrane at warm temperatures Membrane Proteins: proteins embedded in bilayer that serve various functions such as transporting substances across the membrane (transport proteins), receiving chemical signals (receptor proteins), cell- cell recognition (recognition proteins).

7. Diffusion

8. Diffusion Does Not Require Energy

9. Osmosis = diffusion of water

10. Osmosis

11. Blood cells in isotonic solution (0.9% NaCl) Blood cells in hypertonic solution (1.01% NaCl) Blood cells in hypotonic solution (0.65% NaCl)

12. Some single-celled organisms must actively regulate water balance

13. Facilitated Diffusion vs. Active Transport