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Lecture # 13: Biological Actuators

2) Bacterial rotors. 1) Osmotic motors. 4) striated muscles. 3) Molecular rack and pinions. Lecture # 13: Biological Actuators. trigger. high Ca2+. high osmotic pressure. H 2 0 influx. www.niwascience.co.nz. http://upload.wikimedia.org. www.jcu.edu.au. 1. Osmotic Motors

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Lecture # 13: Biological Actuators

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  1. 2) Bacterial rotors 1) Osmotic motors 4) striated muscles 3) Molecular rack and pinions Lecture # 13: Biological Actuators

  2. trigger high Ca2+ high osmotic pressure H20 influx www.niwascience.co.nz http://upload.wikimedia.org www.jcu.edu.au 1. Osmotic Motors e.g. nematocyst Cnidarians: Jellyfish Corals Hydroids

  3. www.gay-dive.com

  4. ‘run & tumble’ behavior During run, flagella spin in same direction. During tumble, one or more flagella change direction. Howard Berg 2. Bacterial Rotors

  5. E.Coli uses a ‘biased random walk’ to search for food in a complex 3D landscape.

  6. rigid filament structure of bacterial rotor artist’s reconstruction rigid ‘rotor’ composed of many proteins 40 nm ‘stator’ reconstruction from Electron Micrograph www.arn.org ‘rotor axis’ • Key features of bacterial rotors: • only true ‘wheel’ in Nature • driven by proton pump • ~400 steps/rotation • operates at ~ 50 Hz • super efficient (90%)

  7. Eukaryotic cells possess a complex cytoskeleton: actin network throughout cell microtubules associated with nucleus 3. Molecular ‘Rack and Pinions’ www.sparknotes.com These twostructural systems are associated with specifc motors.

  8. Structure of actin and tubulin filaments

  9. - + dynein kinesin cargo attachment cable converter domain ATP binding cleft tubulin binding site Two motors run on tubulin: kinesin and dynein operates as ‘hand-over-hand’ dimer

  10. dynein has special role as cilia/flagella motor

  11. myosin has structure similar to kinesin

  12. myosin plays important role in muscle contraction

  13. sliding filament model sarcomere

  14. electro-mechanical coupling

  15. Ca2+ binds here

  16. 2) Bacterial rotors 1) Osmotic motors 4) striated muscles 3) Molecular rack and pinions Lecture # 13: Biological Actuators

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