The surface area to volume ratio of a cell affects which of the following?

• A. The rate of exchange between the cell and its environment
• B. The speed of DNA replication
• C. The rate of protein synthesis
• D. The cell's genetic code

Answer: (A)

The amount of material a cell can exchange with its surroundings depends on the surface area of the cell membrane, while the amount that must be moved depends on the cell’s volume. The surface area sets how many transport proteins and channels are available for substances to cross per unit time, so a larger surface area relative to volume allows faster exchange. But as a cell grows, its volume increases faster than its surface area, lowering the surface area to volume ratio and making exchange less efficient. That’s why SA:V strongly influences how quickly nutrients enter and wastes leave the cell.

The other options aren’t governed by this geometric trait: the speed of DNA replication and the rate of protein synthesis depend on cellular machinery and energy supply, not membrane surface area; and the genetic code is determined by DNA sequence, not by the cell’s size or shape.