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Biology problem (sorta physics like actually)

  1. Feb 13, 2007 #1
    Within a monolayer phospholipid molecules exchange places with their neighbors every 10^-7 seconds. It takes about 1 second for a phospholipid to diffuse from one end of the bacterium to the other, a distance of about 2 micrometers.

    A) Are these numbers in agreement? Assume that the diameter of a phospholipid head is 0.5 nm. Explain why or why not.

    B) To gain an appreciation for the speed of molecular motions, assume that a lipid molecule is the size of a ping pong ball (4 cm diameter) and that the floor of your living room (6 m by 6 m) is covered wall to wall in a monolayer of balls. If two neighboring balls exchanged positions every 10^-7 seconds how fast would they be moving in km/h? How long would it take for a ball to move from one end of the room to another?

    I am not sure where to begin with these and what type of equations to use. If anyone can at least help me begin thatd be greatly appreciated!
  2. jcsd
  3. Feb 13, 2007 #2
    if the head is 0.5 nm, and the lipid exchanges places every 10E-7s, then it is moving at 0.5nm per 10E-7s, or 5E-4 m/s (convert .5 nm to meters, divide by seconds, to get its velocity)

    if it takes 1 second to travel 2 micrometers, then it travels from one end of the bacterium to the other, at an average of 2E-6 m/s (convert 2 um to meters, divide by 1 second to get its velocity)

    yes they are in agreement, because the speed that it is zipping around at (exchanging places with neighbors) is more than the speed required to get to the other side, so randomly exchanging places with neighbors could lead it to the other side within a second

    use same principles as in A to find the velocity (take care with units)

    then rearrange the equation Velocity=Distance/Time so you can see how long it takes to travel 6 meters
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