Figure 29.3
Use the following information when answering the corresponding question(s).
The mechanism of cell crawling in protist species is not well defined.The textbook states that pseudopodia extension involves interactions between actin and myosin (the same molecules that are involved in mammalian muscle contraction).However,prior to the study described below,no one had provided convincing data that actin and myosin were actually involved in cell crawling in protists.Anatomical studies had identified the cytoskeletal protein actin just below the surface of the cell membrane in several species of protist;but physiological studies had failed to show a functional link between actin,myosin,and cell crawling.
In a study by N.Poulsen et al.(Diatom gliding is the result of an actin-myosin motility system,Cell Motility and the Cytoskeleton 44 (1999):23-22),researchers tested whether motility in a particular species of diatom involves interactions between actin and myosin.

-Refer to the study by Poulsen et al.and Figure 29.3.The data graphed in Figure 29.3 could be an artifact if latrunculin A kills this species of diatoms (i.e. ,that may be why the cells are not moving).Which of the following would be the best evidence that latrunculin A is not killing the cells?
A)When the toxin was washed off the culture,the cells began to move again.
B)There were still a small percentage of motile cells in the culture treated with the toxin.
C)Most of the cells in the control were moving,indicating that they were alive.
D)When the toxin was applied to another species of diatom,25% of them continued to move.

Question

Figure 29.3
Use the following information when answering the corresponding question(s).
The mechanism of cell crawling in protist species is not well defined.The textbook states that pseudopodia extension involves interactions between actin and myosin (the same molecules that are involved in mammalian muscle contraction).However,prior to the study described below,no one had provided convincing data that actin and myosin were actually involved in cell crawling in protists.Anatomical studies had identified the cytoskeletal protein actin just below the surface of the cell membrane in several species of protist;but physiological studies had failed to show a functional link between actin,myosin,and cell crawling.
In a study by N.Poulsen et al.(Diatom gliding is the result of an actin-myosin motility system,Cell Motility and the Cytoskeleton 44 (1999):23-22),researchers tested whether motility in a particular species of diatom involves interactions between actin and myosin.
 
-Refer to the study by Poulsen et al.and Figure 29.3.The data graphed in Figure 29.3 could be an artifact if latrunculin A kills this species of diatoms (i.e. ,that may be why the cells are not moving).Which of the following would be the best evidence that latrunculin A is not killing the cells?
A)When the toxin was washed off the culture,the cells began to move again. 
B)There were still a small percentage of motile cells in the culture treated with the toxin. 
C)Most of the cells in the control were moving,indicating that they were alive. 
D)When the toxin was applied to another species of diatom,25% of them continued to move.

Quizplus · Accepted Answer

If the toxin was washed off and the cells began to move again, it would indicate that the toxin was not killing the cells and that the lack of movement seen in Figure 29.3 was indeed due to latrunculin A treatment. This would provide evidence against latrunculin A being an artifact and support the conclusion that actin and myosin are involved in the motility of diatoms. Option B is not as strong of evidence, as a small percentage of motile cells could still be due to a lack of toxin exposure or other factors. Option C is not relevant to the question of whether the toxin is killing the cells. Option D does not pertain to the effects of latrunculin A on the species of diatom being studied.

Figure 29.3 Use the Following Information When Answering the Corresponding Question(s)