Cell size and surface area-to-volume ratio Knowledge-Based Download PDF

Questions

1. 1.

   In a growing spherical cell, how do the capacity for membrane-mediated material exchange and the internal metabolic demand scale with respect to the cell radius $r$?

   • A) Exchange capacity scales with $r^3$, while metabolic demand scales with $r^2$.
   • B) Both exchange capacity and metabolic demand scale proportionally with $r$.
   • C) Exchange capacity scales with $r^2$, while metabolic demand scales with $r^3$.
   • D) Both exchange capacity and metabolic demand scale proportionally with $r^3$.
2. 2.

   When a single large eukaryotic cell divides into smaller daughter cells without any change in total cellular volume, what effect does this division have on the total plasma membrane surface area and the overall surface area-to-volume ratio?

   • A) Both the total surface area and the overall surface area-to-volume ratio decrease.
   • B) The total surface area remains constant, but the overall surface area-to-volume ratio decreases.
   • C) Both the total surface area and the overall surface area-to-volume ratio increase.
   • D) The total surface area decreases, while the overall surface area-to-volume ratio increases.
3. 3.

   Why does an increase in linear dimensions impose an upper physical limit on cell size?

   • A) Volume increases as the cube of the linear dimension while surface area increases only as the square, reducing the relative area available for metabolic exchange.
   • B) Surface area increases as the cube of the linear dimension while volume increases only as the square, leading to unsustainable membrane tension.
   • C) Both surface area and volume increase in direct linear proportion to diameter, but the rate of active transport drops as the membrane thickens.
   • D) Volume increases exponentially while surface area remains constant, causing cytosolic pressure to exceed membrane tensile strength.
4. 4.

   Which morphological characteristic enables a cell to maintain a significantly higher surface area-to-volume ratio compared to a spherical cell of identical volume?

   • A) Possessing extensive plasma membrane foldings, such as microvilli, or adopting an elongated, flattened shape
   • B) Adopting a smooth spherical conformation to minimize external membrane exposure
   • C) Expanding total cytoplasmic volume while keeping the outer boundary completely smooth
   • D) Reducing plasma membrane surface area while maintaining a constant internal volume
5. 5.

   As a growing cell increases in diameter, how does its surface area-to-volume ratio change, and what biological challenge does this pose?

   • A) The ratio increases, causing excessive loss of water and ions across the membrane.
   • B) The ratio remains constant, keeping cellular transport independent of cell size.
   • C) The ratio decreases, limiting the efficiency of nutrient uptake and waste removal across the plasma membrane.
   • D) The ratio decreases, which speeds up internal diffusion to meet metabolic demands.