Question

a researcher growing cells in culture observed that the cells always divided once they reached a certain size. when she added more nutrients to the culture medium or adjusted the temperature of the growing chamber, the cells grew at different rates but always divided once they reached a certain size. which statement explains these observations? as they grow, cells require greater and greater quantities of nutrients from the environment, and they must reduce this requirement by dividing. the cells surface area increases faster than its internal volume as it increases in size, and this leads to an inability of the cell to feed itself. efficiency of transport of materials within a cell decreases with size, thus limiting the maximum cell size. increasing cell size is accompanied by increasing cellular reactions, which produce more heat that threatens cell survival. the increasing surface area of a cell as it grows larger increases the risk that small molecules that can harm the cell will pass from the environment into the cell interior.

Explanation:

As a cell grows, its volume increases faster than its surface - area. This leads to a decrease in the surface - area to volume ratio. The transport of materials into and out of the cell occurs across the cell membrane (surface area). A lower surface - area to volume ratio means less efficient transport of nutrients and waste, thus limiting cell size. When the cell reaches a certain size where transport is no longer efficient enough, it divides.

Answer:

Efficiency of transport of materials within a cell decreases with size, thus limiting the maximum cell size.