L23 - Friday,November19,2010...

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

View Full Document Right Arrow Icon
Friday, November 19, 2010 Cell Movements I: Subcellular Freeways Reading: Chapter 17, pages 571 – 572  &  577 – 592 (skip "Intermediate Filaments"  section)  Objectives It has become increasingly clear that cells are highly  organized o Early biochemists: a "bag of enzymes" o Later biochemists: many enzymes are in organelles, but the organelles float  around freely o Current wisdom: organelles are arranged in specific ways, highly  organized. It is also clear that cells and intracellular structures are extremely  dynamic The system that allows cells to be organized and dynamic is the  cytoskeleton     .     o Consists of a network of interconnected  tubules and filaments  in the  cytosol. o Gives cells shape and mechanical strength. o Serves as a scaffold for the movement of organelles. The two major classes of cytoskeletal elements are  microtubules  and  microfilaments . (A third class is intermediate filaments, but they are more  specialized and variable in function.)  Microtubules:  o 25 nm in diameter (about 1/4 the diameter of a clathrin-coated vesicle) o made up of polymerized  tubulin Microfilaments:  o 7 nm in diameter o made up of polymerized  actin Microtubule assembly is initiated at the  microtubule-organizing center (MTOC) a.k.a. the  centrosome
Image of page 1

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

View Full Document Right Arrow Icon
Microtubules (and actin filaments) have a polarity: the two ends are different.  EACH END IS POLYMERIZED. NORTH/SOUTH o One end is arbitrarily called plus ("+"), the other minus ("-"). o The minus end of every microtubule is anchored in the MTOC. Thus,  microtubules can only grow at their plus ends. Microtubules  are actually composed of two kinds of tubulin:  α -tubulin and  β -tubulin.  o The unit of microtubule assembly is a dimer of  α - and  β -tubulin.  Polymerize in this end to end fashion.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern