A) Each protofilament in a microtubule is assembled from subunits of alpha-tubulin and Beta-tubulin subunits. Please describe how the organization of the subunits contributes to the protofilament’s polarity and differences between the two ends. How does this polarity contribute to the directionality of two major types of microtubule assisted motor proteins?

B) When microtubules grow out of centrosome, which end is associated with the centrosome?