Final answer:
The partition coefficient of a molecule indicates its lipid solubility, which determines its ability to permeate cell membranes. The plasma membrane's lipid bilayer favors lipophilic molecules for passive diffusion, influenced by factors like fluidity and temperature.
Step-by-step explanation:
The partition coefficient (P.C.) of a molecule is indicative of its solubility in lipids, which is related to its membrane permeability. Because the plasma membrane is composed of a lipid bilayer, molecules that are more soluble in lipids can more easily diffuse through it. The property of selective permeability of membranes allows certain substances to pass through while excluding others, which is crucial for maintaining cellular homeostasis.
Lipid solubility directly affects a molecule's ability to cross a cell membrane; molecules that are lipophilic (lipid-loving) and have a higher partition coefficient can pass through the membrane more easily. This is because the interior of the cell membrane is hydrophobic, thus molecules that are also hydrophobic or nonpolar can interact with and dissolve in this lipid environment, facilitating their movement across the membrane by passive diffusion. Factors like temperature and the presence of cholesterol in the membrane influence its fluidity, which can also affect the rate of passive transport.