3.2.2.P5

In a study of the forces involved when motor proteins move subcellular structures in cells, Shtridleman et al.* studied the motion of objects in living cells.  In this paper, they extracted the position of a vesicle using video.  Some of the frames are shown in the figure at the left below and a graph of the position of one of the vesicles that moved along a straight line (in a direction they call y) is shown at the right.

Six instants of time are identified on the graph at the right and labeled by the letters A through F. Assuming that a smoothed model of the motion is appropriate for understanding the forces involved, choose the letter for the instant of time that would represent the events labeled in parts 1 through 4 below.

1.  The instant of time at which the vesicle is moving with the highest speed.

2.  The instant of time at which the vesicle is moving with the slowest speed.

3.  The instant of time at which the vesicle feels net force of the largest magnitude.

4.  The instant of time at which the magnitude of the vesicle’s acceleration is the largest.

For the items 5 and 6 below choose the item (a) through (c) that is the best match.

* Force-Velocity Curves of Motor Proteins Cooperating In Vivo, Y. Shtridelman, et al., Cell Biochem Biophys. 52(1): 19–29 

Joe Redish 12/29/11