Which factor does not affect the diffusion of substance through the cell membrane?
**Core Concept**
The diffusion of substances through the cell membrane is a passive process governed by the concentration gradient and the lipid solubility of the substance. This process is primarily facilitated by the fluid mosaic model of the cell membrane, where lipids and proteins interact to allow substances to pass through.
**Why the Correct Answer is Right**
The correct answer is related to the concept that the diffusion of substances through the cell membrane is not affected by the pH of the surrounding environment. This is because the cell membrane's lipid bilayer is not significantly affected by pH changes, and the diffusion process is primarily driven by the concentration gradient and lipid solubility.
**Why Each Wrong Option is Incorrect**
**Option A:** Concentration gradient - This is a key factor that affects the diffusion of substances through the cell membrane. A higher concentration gradient will drive the diffusion process.
**Option B:** Lipid solubility - This is another crucial factor that affects the diffusion of substances through the cell membrane. Substances with high lipid solubility will diffuse more easily through the lipid bilayer.
**Option C:** Temperature - Temperature affects the kinetic energy of molecules, which in turn affects the diffusion process. Higher temperatures will increase the diffusion rate.
**Clinical Pearl / High-Yield Fact**
The lipid bilayer's fluidity affects the diffusion of substances through the cell membrane. An increase in temperature will increase the fluidity of the lipid bilayer, allowing substances to diffuse more easily.
**Correct Answer:** D. pH of the surrounding environment.