The rate of diffusion for a given solute is determined primarily by

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The rate of diffusion for a given solute is determined primarily by

Diffusion across a membrane is determined by how easily the membrane allows the solute to cross. The rate depends primarily on the permeability of the phospholipid bilayer to that solute: if the solute is lipid-soluble or small and nonpolar, it passes through the bilayer readily and diffusion is fast; if the solute is large, polar, or charged, it crosses slowly unless aided by channels or transporters. The other options don’t set the rate of passive diffusion: the color of the solution is irrelevant to membrane transport, the size of the nucleus does not influence how molecules move through the membrane, and the presence of mitochondria does not directly change the bilayer’s permeability to a given solute.

Diffusion across a membrane is determined by how easily the membrane allows the solute to cross. The rate depends primarily on the permeability of the phospholipid bilayer to that solute: if the solute is lipid-soluble or small and nonpolar, it passes through the bilayer readily and diffusion is fast; if the solute is large, polar, or charged, it crosses slowly unless aided by channels or transporters. The other options don’t set the rate of passive diffusion: the color of the solution is irrelevant to membrane transport, the size of the nucleus does not influence how molecules move through the membrane, and the presence of mitochondria does not directly change the bilayer’s permeability to a given solute.

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