BIO 1000 Lecture Notes - Lecture 13: Dynein, Microfilament, Cilium
4 Mar 2017
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Document Summary
In spite of their differences, both cilia and flagella have the same ultrastructure. Both have a core of microtubules sheathed by the plasma membrane. Nine doublets of microtubules are arranged in a ring around a pair at the center. This 9 + 2 pattern is found in nearly all eukaryotic cilia and flagella. Flexible wheels of proteins connect outer doublets to each other and to the two central microtubules. The outer doublets are also connected by motor proteins. The cilium or flagellum is anchored in the cell by a basal body, whose structure is identical to a centriole. The bending of cilia and flagella is driven by the arms of a motor protein, dynein. Addition and removal of a phosphate group causes conformation changes in dynein. Dynein arms alternately grab, move, and release the outer microtubules. As a result, the forces exerted by the dynein arms cause the doublets to curve, bending the cilium or flagellum.
