Question

The primary function of the kidney is to exchange molecules across a membrane between the blood and the urine. One type of kidney cell has a basic rectangular shape, except for a single surface, which is lined with tiny, finger-like projections that extend into the surrounding extracellular space. Which of the following best explains the advantage these projections provide the cell? The projections increase the volume of the cell without affecting the surface area, which increases the metabolic needs of the cell. B The projections increase the surface area-to-volume ratio of the cell, which allows for more efficient nutrient exchange with the environment. The projections increase the speed at which an individual molecule can move, resulting in faster nutrient Which of the following best explains the advantage these projections provide the cell? A The projections increase the volume of the cell without affecting the surface area, which increases the metabolic needs of the cell. B The projections increase the surface area-to-volume ratio of the cell, which allows for more efficient nutrient exchange with the environment. The projections increase the speed at which an individual molecule can move, resulting in faster nutrient exchange with the environment D The projections increase the selectivity of the membrane because the small size of the projections limits the number of transport proteins that can be embedded in the membrane.

Answer 1

The answer is B: The projections increase the surface area-to-volume ratio of the cell, which allows for more efficient nutrient exchange with the environment.

Step-by-step explanation:

These finger-like projections, also known as microvilli, are commonly found in cells that are actively involved in absorption or secretion, such as the kidney cells in this scenario. They significantly increase the surface area of the cell, thereby allowing more transport proteins to be embedded in the cell membrane and facilitating more efficient exchange of molecules between the cell and its environment. This increase in surface area doesn't significantly affect the volume of the cell, so it doesn't considerably increase the metabolic needs of the cell.

Therefore, these projections do not primarily increase the volume of the cell (option A), the speed of individual molecule movement (option C), or the selectivity of the membrane by limiting the number of transport proteins (option D). Instead, they enhance the cell's capacity for molecular exchange by increasing its surface area.