How might the cell-surface membranes of uterine lining cells be adapted for nutrient transport?

The choice indicating increased surface area for diffusion is particularly insightful when considering the role of uterine lining cells in nutrient transport. Cells that have an enhanced surface area, such as those in the uterine lining, can efficiently absorb and transport nutrients due to a larger area available for the interaction with substrate molecules. This adaptation facilitates greater diffusion rates as more molecules can simultaneously bind and pass through the cell membrane.

The increased surface area can be achieved through various structural adaptations, such as microvilli, which are small finger-like projections that extend from the cell surface. These structures not only increase the area available for diffusion but also enhance the cell's ability to uptake specific nutrients essential for supporting embryonic development and maintaining the uterine environment. This is crucial during the early stages of pregnancy when the uterus provides nourishment to the developing embryo before placental formation.

Other adaptations, such as those mentioned in the other choices, would not necessarily favor efficient nutrient transport. For example, thickened membranes may impede rather than facilitate diffusion, fewer protein channels could limit transport capabilities, and a lower number of active transport proteins would hinder the cell’s ability to move nutrients against their concentration gradient, which is often necessary for optimal nutrient absorption and maintenance of cellular needs.