Chapter 4, Problem 1A

Summary Introduction

Introduction:

A cell requires a large surface area to allow the movement of nutrients within the cell and the waste outside the cell. Small cells have an adequate amount of surface area to facilitate the exchange of nutrients and waste. With an increase in the size of the cell, the surface area becomes inadequate for the exchange of nutrients and wastes that the cell volume requires.

Explanation of Solution

Correct answer:

The surface-area-to-volume ratio defines the size of a cell. Therefore, option (c) is correct.

Explanation for the correct answer:

The sizes of the cells vary in terms of their range. Some of them are very small and some of them are large. In a cell, where the ratio of the surface area to volume is more, the size of the cell would be small and where the surface area to volume ratio is less, the size of the cell would be large.

Option (c) is given as “its size”. As, “the surface-area-to-volume ratio defines the aspect of size of cell”, it is the right answer. Hence, option (c) is correct.

Explanations for incorrect answers:

Option (a) is given as “whether it is eukaryotic or prokaryotic”. The eukaryotic or prokaryotic cells are defined on the basis of the presence or absence of the membrane bound nucleus. So, it is a wrong answer.

Option (b) is given as “whether it is plant or animal”. The animal cell and plant cell are defined on the basis of the presence or absence of the cell wall. So, it is a wrong answer.

Option (d) is given as “its ability to move”. The ability to move is defined by the presence of cytoskeleton (cilia or flagella) in a cell. So, it is a wrong answer.

Hence, options (a), (b) and (d) are incorrect.

Conclusion

The size of the cell is defined by surface-area-to-volume ratio.