1. Cell and Developmental Biology Biology 52 Section 7 Fall Semester, 2002 Tues, Thurs 9:30 - 10:45 am Coker Hall 201 Syllabus make sure you download the lecture guide and notes before each class make sure you download the lecture guide and notes before each class Aug. 20 Protein Structure I (Chapter 3, pp 50-59, 62-64) plus recitation reading 22 Protein Function and Biomembranes (Chapter 3, pp 68-71; 74-81; Chapter 5, pp 157-159) 27 Biomembranes and Subcellular Organization of Eukaryotic Cells (Chapter 5, pp 160-166, 168-170, 172-176) Plus recitation reading last updated on 08/20/02

3. Several types of evidence point to the universality of the phospholipid bilayer This is not intuitive knowing that: 1. organelles have unique membrane Compositions, mitos 76% protein, Myelin, 18% 2. Phospholipid composition varies However: 3. Lipids spontaneously form b/lyrs  4. Microscopies are consistent with b/lyrs

4. Erthrocytes are ideal for membrane studies Osmium tetroxide binds polar heads

5. All integral proteins and glycolipids bind assymetrically to the bilayer NO FLIP FLOP Protein assymetry is established during translation Glycosylation occurs after lipid insertion Phospholipid composition differs between the two leaflets Positive head groups are favored on outside, negative inside NO FLIP FLOP Assymetry is established by a “flipase” Local regions like caveolae have special phospholipid composition Enzyme function is affected by microenvironment

6. Most lipids and integral proteins are laterally mobile Two expts make this point: Cell fusion  and FRAP

7. Fluoresence Recovery After Photobleaching, FRAP What does FRAP tell us? Most P’lipids and proteins are mobile but less mobile in real bilayers than artificial ones.

8. But mobility can be constrained … a.Cytoskeletal interactions b.Extracellular matrix interactions c.Interactions between proteins within a raft.

9. Fluidity of the membrane depends on temperature and composition Phase change Increases fluidity: unsaturated FA, short chain FA, protein, cholesterol Cholesterol can also decrease fluidity

10. Membrane leaflets can be separated and each face viewed individually

11. Here’s another way to look at this technique:

14. ORGANELLES OF THE CELL - A QUICK TOUR (much more detail later)

16. Plant cells differ in some aspects. Cellulosic cell wall Large central vacuole Additional organelles

17. Lysozomes. Variable size and shape, 100’s/cell, closed compartment, single membrane, degradative compartment, acidic, low pH maintained by H+/Cl- ATPases, pH optimum for lysozomal enzymes is acidic. Tay-Sachs Disease is an example of a hydrolase minus, organelle maturation primary and secondary, key compartment for phagocytosis, endocytosis, autophagy