01-10 Orgnls&Epith (1)

01-10 Orgnls&Epith (1) - ORGANELLES AND EPITHELIUM...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
ORGANELLES AND EPITHELIUM ORGANELLES Many of the first set of class slides are from the Cell Biology textbook by G. Karp. These slides are indicated by the chapter and figure numbers from the 5 th edition ( K5 ). These slides and all other, non-Karp, slides can be found on the reserved CDs in the library. 1 ( 4.4b K5) The original Singer-Nicholson fluid mosaic model. The fluid mosaic model of cell membranes: the lipid polar head groups are oriented away from the hydrophobic fatty acid domains of the amphipathic, bilayer-forming lipid molecules. Van der Waals associations among fatty acid hydrocarbon chains hold the bilayer together. Differences in composition of FAs primarily (and PHGs slightly) are responsible for differences in physical properties such as viscosity among membranes of different lipid compositions. 2. ( Page 121 Karp 4, 120 K5) A nice reconstruction of the relationships among lipids and water molecules. Thermal energy causes FA tails to wave about, creating small cavities, and water molecules occasionally diffuse into such cavities and then, on a probabilistic basis, further into the bilayer by diffusing into newly-opened spaces. A few such water molecules move entirely through a membrane. This is the basis of osmosis. It relies solely on heat and random creation of spaces.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
3 ( 8.9a Karp 5 th ed ( K5) ) The RER is Composed of Cisternae and Tubules . Cisternae are flattened, balloon-like regions of ER while tubules are connecting tubes between cisternae. The entire ER, rough and smooth, plus the nuclear envelope mebranes are composed of a single lipid bilayer. The 3 regions of the membrane have different physical properties because ‘domains’ exist that have properties different from each other (ie, different lipid composition, IMPs, etc). Rough ER is that which carries out protein synthesis of proteins which pass into the ER lumen (inside space) or become integral to the membrane. The ‘rough’ or RER is the image of ribosomes studding the outer monolayer of ER. Different cell types have different proportions of RER cisternae and tubules – those more engaged in secretion tend to have more cisternae than those not actively secreting proteins. Most cells rarely if ever have lots of cisternae. All cells need RER to carry out IMP turnover but the amount of RER needed for that is small; tubular RER is sufficient. Smooth ER is the same organelle as RER but it has particular activities mostly different from those of RER. One activity clearly shared by RER and SER is storage of calcium ions in the lumen at high concentration; about 10 -5 to 10 -6 M. 4. (8.9c, K5) Scanning EM of RER Proteins are synthesized at 2 distinct locales within cell. Some are made on ribosomes attached to IMPs at the cytosolic surface of RER membranes. These are (1) proteins secreted from cells, (2) integral membrane proteins, and (3) soluble proteins that reside within compartments of endomembrane systems (ER, Golgi complex, lysosomes, endosomes, vesicles, plant vacuoles). These are all proteins that cross through or embed
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/16/2010 for the course BIO 542 taught by Professor Dr.philipbonner during the Spring '10 term at Kentucky.

Page1 / 14

01-10 Orgnls&Epith (1) - ORGANELLES AND EPITHELIUM...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online