Cell Membrane

Function Separates cytoplasm from external environment Regulates what enters and leaves cell Cell identification Cell-cell communication

Plasma membrane regulates movement of materials due to its chemical composition: Phospholipids Cholesterol Proteins

Phospholipids Phospholipids Bilayer Phospholipids have: Hydrophilic head Nonpolar hydrophobic tail Phospholipids Bilayer

Hydrophilic "heads" faces the watery environment inside and outside cell Hydrophobic tail forced to face inward – away from water.

The phospholipids are not bound together – gives the membrane a fluid nature

CHOLESTEROL Function: Stabilizes membrane (structural support) Cell communication (cell-cell and cell- hormone)

Some interesting facts Most common molecule in membrane (>50%) Due small size and weight – only 20% of membrane mass Is an amphipathic molecule Homework – find out what this means

Proteins Are embedded in membrane Serve different functions

Functions 1. Channel Proteins - small openings for molecules to diffuse through 2. Carrier Proteins- binding site on protein "grabs” molecules, pulls them into cell 3. Receptor Proteins – act as triggers that set off cell responses (such as release of hormones or opening of channel proteins) 4. Cell Recognition Proteins - ID tags, identify cell to immune system 5. Enzymatic Proteins - carry out metabolic reactions

LABEL YOUR DIAGRAM WITH THE FOLLOWING DETAILS

Task: Due end of class Read pages 47 -49 in your text Answer questions 1 – 5 in practice section Explain the structure and function of glycoproteins. How are liposomes used in cancer treatment and gene therapy? What role might receptor proteins have in medical disorders such as Hypertension?