BIO 1140 Study Guide - Midterm Guide: Microfilament, Tubulin, Kinesin
6 Apr 2018
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Why is this polarity important in microtubule function? (4 marks) The microtubule, like microfilaments, are oriented due to their structural polarity. Microtubules are made of alpha and beta tubulin subunits that have gtp binding sites. When the microtubule forms from the stacking of these tubulin molecules, the positive side, the beta side, exposes the. Gtp binding site whereas the negative, alpha side has the gtp binding site hidden in the dimer. This contributes to the polarity of the microtubule, making the negative gtp exposed location the primary site for addition of additional tubulin monomers. This polarity is important for cell motility where the orientation of the microtubule will determine which way the dynein and kinesin motor travel. The dynein transports vacuoles, organelles and other cellular substances towards the negative end of the microtubule while kinesin does the same but to the positive end.
