1. Membranes Everything in life is variable –Chaotic Membranes organize the chaos of cellular metabolism –E.g. houses & stores with doors & gates –E.g. streets organize traffic Selectively permeable –Allows some things in & blocks some things Plasma membrane (cell) –Takes up what cell needs & takes out the trash

2. Thin, requires EM at 200,000x 3 zones –Construction of Phospolipids

3. Phospholipid Polar, hydrophilic head –Phosphate group –React and interact with the environment Non-polar, hydrophobic tail –Two-tailed fatty acid

4. Relation w/ water = Phospholipid Bi-layer –Non-polar, hydrophobic molecules move more freely through the membrane (soluble in lipids) E.g. vessicles and vacuoles transporting packages throughout membrane system E.g. soap to clean (breakdown) grease –Polar molecules & ions not soluble

5. Membrane = Fluid mosaic of phospholipids and proteins

6. Mosaic –Made up of many small pieces

7. Mosaic = diverse proteins embedded in phospholipids Fluid = proteins can drift laterally within bi-layer

8. Cholesterol – helps stabilize at body temperature & maintains fluidity at lowered temperatures Glycolipids & glycoprotiens –Carbohydrate ID tags E.g. immune system recognizes good cells from bacterial cells E.g. embryonic development – cells differentiate (tissues & organs) Proteins – do most of the work

9. Membrane Proteins Very diverse –E.g. >50 different proteins in plasma membrane of human blood cells Enzymes – catalyze molecule assembly (e.g. modify by increasing rate) Receptors – messengers from other cells (e.g. hormones) Transport – allows large molecules to pass

10. Passive Transport = diffusion Diffusion = natural tendency of particles to spread evenly (from high concentration to low concentration) to reach balance No energy required

11. Many smaller molecules simultaneously E.g. O 2 and CO 2 move in & out of rbc’s

12. Facilitated Diffusion Size or polarity prevents diffusion? Protein creates a channel or pore for passage –E.g. sugars, amino acids, ions, & water Down concentration gradient (high conc. to low conc.) Passive transport –No energy required

13. Active Transport Spends energy to push solutes against conc. gradient Passive transport down a gradient is “as easy as falling in a hole” But, how do you climb back up/out? Use the notches/cracks/crevices, but takes energy - ATP

14. Transport of LARGE molecules Exocytosis – transport out of cell –Vesicle (membrane package) fuses with plasma membrane, opens, releases outside –E.g. salty tears from tear glands

15. Endocytosis – reverse of exocytosis –bringing in macromolecules from outside of plasma membrane –Pinching of membrane to form vesicle

16. Phagocytosis – cellular eating –Engulfs food molecules forming a vacuole, fuses with lysosomes for digestion E.g. Amoeba Pinocytosis – cellular drinking –Vesicles of non-specific liquid Receptor mediated endocytosis –Pit forms in plasma membrane that is lined with specific receptors, pinches closed, releases molecules inside cytoplasm