1. Membrane: Structure and Function
Chapter 5.10+

2. What you need to know! Why membranes are selectively permeable.
The fluid mosaic model structure.
The role of phospholipids, proteins, and carbohydrates in membranes.

3. All Membranes Barriers between interior and exterior
Help maintain homeostasis
Allow for compartmentalization (eukaryotes)
Semi-permeable (selectively) permeable
Permeable: gas, H2O, entering nutrients, exiting waste
Impermeable: harmful substances, microorganisms
Controls ion exchange
Made from phospholipids

4. Phospholipid Bilayer Phospholipids in water will form a bilayer
The heads are hydrophilic and face outward (toward water)
The fatty acid tails are hydrophobic and face inward (away from water)

5. Fluid Mosaic Model Structure can be observed with EM
Mosaic of floating phospholipids with cholesterol, proteins, and carbohydrates (glycoproteins/ glycolipids)
Flexible and in constant motion
Think of a soap bubble skin rather than saran wrap

6. Fluidity
Unsaturated fatty acids create kinked tails which help spread out the membrane and maintains fluidity
Cholesterol embedded in animal membranes helps maintain fluidity

7. Proteins Add Function
Transport Proteins: move things in and out of the cell
Enzymes: catalyze chemical reactions inside or outside of the cell
Signal proteins: signal molecules outside the cell trigger chain reactions inside the cell

8. Extracellular Matrix (ECM)
Glycolipids & glycoproteins are carbohydrates attached either to proteins or phospholipids
These act as cell labels for cell-cell identification
Important in development and immune system recognition
Animal Cells: Glycoproteins also act as glue, holding cells together:
Tight Junctions: leak-proof sheet (digestive tract)
Anchoring junctions strong and flexible (skin and muscles)
Gap junctions: passages from one cell to the next for fast transport (heart coordination)

9. Plant Cells Plants do not have an ECM
The cells are stacked, one on top of the other with little room for extracellular molecules
Plasmodesma: channel between plant cells
Fast transport of water nourishment and chemical messages (hormones)