Transcript Lecture 2
Lecture 2 Monday, January 26, 2004 • Survey • Introduction continued :CSK, tensegrity. • Basic cellular components Geodesic- Buckminster Fuller A geodesic dome uses a pattern of self-bracing triangles in a pattern that gives maximum structural advantage, thus theoretically using the least material possible. (A "geodesic" line on a sphere is the shortest distance between any two points.) Nucleus connected to the CSK, modeled with straws. Tensegrity How does the CSK provide structure? Signals travel at speed of sound, as expected for a tensegrity model. Some results are not compatible with tensegrity model With or without microtubules Percolation: an alternate theory LA Figure 1.9 Hypothetical telephone network in the U.S. NY Malines, Belgium Fibroblast Pulling out the chromosomes A micropipet can suck up the end of a chromosome and then the entire 23 Can be pulled out, indicating they are all connected. Cells incorporate into Nano-fabricated devices Attaching to needles Stretching on a cantilever Growing on electrodes The generic cell Basic structure And components Building blocks • • • • • • Water Cl, Na, K, Ca, Mg (50) Fatty acids-lipids- (200) Amino Acids- (115) Sugars- (100) Sugars + Bases (200) H2O Electrolytes Phospholipids Proteins Carbohydrates Nucleotides • 30-200 Daltons 103 -106 Daltons • I.e number of aa’s for spectrin = 230,000 D • 115 Compound Water Fraction in Relative Size Cell of molecule (%) 70-80 Small Polarity of molecule Polarized Protein (Polypeptide) 10-20 Large Regionally polarized Lipid (Fat) 2-20 Medium Non-Polarized Carbohydrate (Sugars) 1-2 Medium to large Regionally polarized Salts (Electrolytes) 1 Small Polarized Lipid vesicles are ghost-like 3. Vesicles pass through each other. 2. Pipet pushes vesicle out. 1. Vesicles make contact H2Polar O Phosphate Heads H2O 70 A H2O Hydrophobic core Proteins • Primary, secondary, tertiary, quaternary structures • Make filaments: rods, tubes, • Flexural Stiffness Kf Y I IR 4 Rod Bending Polymer Length-stiffness • Persistence length • Acid-base reactions determine charge, that determines mechanical properties . • HA H+ + A- • pKa=pH +log[HA] • [A-] Cell inside is a gel : a state of matter whereby electro-osmosis produced by charged polymers causes water pressure inside. Cartilage H20 Swelling pressure = osmotic pressureelastic (compressive) pressure Polymer-polymer Intra-polymer osmosis Factors Ca++, pH Structure by light & immunofluorescence PMT Filter Fibroblasts are stained with Phallacidin green for F actin, Texas red for microtubules, and DAPI for nucleic acid. F actin microtubules F actin is green with Phalloidin, G actin is red with Texas red. Nucleus has fewer stress fibers, but is thicker than rest of cell, so red is diffuse. F actin G actin Studying the CSK: “Knock-out” methods • • • • Spectrin Actin Microtubules Intermediate Filaments • • • • Heat Cytochalasin Nocodazole Acyrlamide Swelling and Lysis to measure membrane strength • RBCs Muscle Frog 3% 50% Pipet Aspiration Neutrophils are WBCs involved in immune response. The source of cortical tension is unknown, but may be from actin tangential to surface. Cells are Wiggly and Soft New ways to describe softness- difference between cooked and uncooked noodles: thermal fluctuations. Neutrophils are WBCs involved in immune response. The source of cortical tension is unknown, but may be from actin tangential to surface. Fibroblast dividing