Wednesday, August 25, 2010

Cilia vs Flagella

I was having another read over the chapter before class, and I remembered that there was one section that I had planned to write a post on, but hadn't, which is the difference between flagella and cilia.
From biology lessons, we know that there are a number of differences that exist between eukaryotic cells and prokaryotic cells, and one of these is the difference between appendages for motion.
Most cells use cilia - 5-10 um long, 200nm diameter, and whip like. Non-stationary cells use them for motion, while stationary ones use them to sweep food or pump fluid. there are internal motors which allow for cross-motion of the cilia, and the motion is periodic. The propulsion is generated from an intuitive result of the Reynold's number (statement 5.15 in the textbook). On another note, the power stroke sends the cilium perpendicular to its axis, and the recovery stroke parallel. This motion allows for only part of its motion to be undone by the recovery stroke, allowing for overall net displacement after each stroke cycle.
Bacteria on the other hand use flagella, which unlike the cilia, are not whip like and loose, but rigid twisted rods, only 20nm thick. Propulsion is attained through rotary motion by the flagella motor, just like a boat motor.

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