{"id":786,"date":"2019-08-28T23:45:53","date_gmt":"2019-08-29T03:45:53","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/physicsforlifesciences1phys1108\/?post_type=chapter&p=786"},"modified":"2019-10-03T10:57:44","modified_gmt":"2019-10-03T14:57:44","slug":"5-5-viscous-forces-in-cells","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/physicsforlifesciences1phys1108\/chapter\/5-5-viscous-forces-in-cells\/","title":{"raw":"5.5 Viscous forces in cells - Flagellum","rendered":"5.5 Viscous forces in cells – Flagellum"},"content":{"raw":"

Flagellum<\/h1>\r\nAs Wikipedia[footnote]https:\/\/en.wikipedia.org\/wiki\/Flagellum[\/footnote] explains\u00a0<\/span>flagellum<\/b>\u00a0<\/span>(\/f<\/span>l<\/span>\u0259<\/span>\u02c8<\/span>d\u0292<\/span>\u025b<\/span>l<\/span>\u0259m<\/span><\/span>\/<\/a><\/span><\/span>; plural:\u00a0<\/span>flagella<\/b>) is a lash-like appendage that protrudes from the\u00a0<\/span>cell body\u00a0<\/a>of certain\u00a0<\/span>bacteria<\/a>\u00a0<\/span>and\u00a0<\/span>eukaryotic<\/a>\u00a0<\/span>cells termed as\u00a0<\/span>flagellates<\/a>. A flagellate can have one or several flagella. The primary function of a flagellum is that of\u00a0<\/span>locomotion<\/a>, but it also often functions as a sensory\u00a0<\/span>organelle<\/a>, being sensitive to chemicals and temperatures outside the cell.[1]<\/a><\/sup>[2]<\/a><\/sup>[3]<\/a><\/sup>[4]<\/a><\/sup>\u00a0<\/span>The similar structure in the\u00a0<\/span>archaea<\/a>\u00a0<\/span>functions in the same way but is structurally different and has been termed the\u00a0<\/span>archaellum<\/a>.[5]<\/a><\/sup>\r\n\r\nFlagella are organelles defined by function rather than structure. Flagella vary greatly. Both prokaryotic and eukaryotic flagella can be used for swimming but they differ greatly in protein composition, structure, and mechanism of propulsion. The word\u00a0<\/span>flagellum<\/i><\/a>\u00a0<\/span>in\u00a0<\/span>Latin<\/a>\u00a0<\/span>means\u00a0<\/span>whip<\/a>.\r\n\r\n \r\n\r\nThe motors are powered by ATP.\u00a0 We will talk more about this important molecule in the energy chapter.\u00a0 \u00a0https:\/\/en.wikipedia.org\/wiki\/Adenosine_triphosphate<\/a>\r\n\r\n \r\n\r\nAn example of a eukaryotic flagellate cell is the mammalian\u00a0<\/span>sperm cell<\/a>, which uses its flagellum to propel itself through the female reproductive tract.[7]<\/a><\/sup>\u00a0 \u00a0Here is a video from the University of Washington, Washington State, USA.\u00a0 \u00a0It shows mouse sperm.\u00a0 It will open automicallyh below if you are reading this book online.\u00a0 \u00a0https:\/\/www.youtube.com\/watch?v=1wRAHHrttYs<\/a><\/span>\r\n\r\n \r\n

Video of mouse sperm swimming\u00a0<\/strong><\/p>\r\nhttps:\/\/youtu.be\/1wRAHHrttYs\r\n\r\n \r\n\r\n \r\n\r\nE. coli bacterium have several flagella.\u00a0 A scholarly article about this motion can be found in the National Centre for Biology.\u00a0 \u00a0Here is a video of E. Coli swimming from the RaoLab.\u00a0 You can find it here:\u00a0https:\/\/www.youtube.com\/watch?v=ZV5CfOkV6ek&feature=youtu.be\u00a0<\/a>\u00a0.\u00a0 If you are reading this book online it will open automatically.\u00a0 \u00a0This is\u00a0E. coli chemotaxis\u00a0 visualized using fluorescent labeling.\u00a0 \u00a0Chemotaxis is the directional movement of an organism or a living motile cell in response to certain diffusible chemicals in the environment.<\/span>\r\n\r\nhttps:\/\/youtu.be\/ZV5CfOkV6ek\r\n\r\nLet us calculate the drag force on an E. Coli.\u00a0 Flagella can rotate at tens of revolutions per second (like a car engine) and act like propellers to provide thrust to the cell. The bacterium E. coli <\/em>is propelled by several flagella and can swim at 20 microns\/second = 2 x 10-5<\/sup> m\/s.\r\n\r\nWe can calculate the drag force on an idealized spherical bacterium swimming in water. For ease of calculation, we assume:\r\n