Passage III

As a living cell's surface area-to-volume ratio (S/V) increases, so does the cell's ability to exchange substances with its environment.

To model this exchange process, different-sized cubes of gelatin were immersed in a dye for 1 minute. Table 1 lists the edge length, surface area, volume, S/V, and per-cent volume of gelatin that was dyed.

Figure 1 shows the S/V of certain rectangular solids and spheres.

Figure 2 shows the volume of certain rectangular solids and spheres as a function of surface area.

Table 2 lists the diameter and surface area of 5 types of spherical ova (egg cells).

Table 2 adapted from Norman K. Wessells and Janet L. Hopson, Biology. ©1988 by Random House, Inc.

18. Based on the information in Table 1, if a cube-shaped plant cell had an edge length of 0. 5 mm, it would have an S/V of:

Answer and Explanation

Your Answer is

Correct Answer is H

Explanation

Method 1, stupid calculation method: when the edge length is 0.5 mm, Surface area=6×L2= 1.5 mm2, volume=L3=0.125 mm3, so S/V=1.5/0.125=12

Method 2, guessing by looking at the table: as can be seen from table 1, Whenever the edge length decreases, the S/V will double, so when the edge length is 0.5 mm, S/V=6×2=12 (reference edge length=1 mm)