SAT Subject Biology Practice Question 428: Answer and Explanation

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Question: 428

18. Unfertilized frog oocytes were bathed in a neutral, isotonic solution (Frog Ringer's solution) to prevent changes in volume due to osmosis. The Frog Ringer's solution was supplemented with radiolabeled amino acids. A sample of oocytes was taken every 30 minutes and assayed for radioactivity.

At Time 1, the oocytes were fertilized. Samples were taken at five-minute intervals after fertilization and assayed for radioactivity. The results are presented in the graph below.

The Frog Ringer's solution in the experiment is described as being isotonic. An isotonic solution

A. has more DNA than another solution
B. has more protein than another solution
C. is more concentrated than another solution
D. is less concentrated than another solution
E. is equally concentrated to another solution

Correct Answer: E


E The experiment description explains that the oocytes were placed into Frog Ringer's solution to prevent changes in volume caused by to osmosis. The only way that osmosis can be prevented is to make sure that the solution the cells are suspended in is equally concentrated to the cells themselves.

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