The major driving force for formation of membrane lipid bilayer is
**Core Concept**
The formation of a membrane lipid bilayer is a crucial aspect of cell membrane structure and function. The major driving force behind this process is the amphipathic nature of lipids, which allows them to spontaneously arrange themselves in a specific orientation, minimizing contact between hydrophobic tails and maximizing contact between hydrophilic heads with the aqueous environment.
**Why the Correct Answer is Right**
The correct answer is van der Waals interactions. These interactions occur between non-polar regions of lipids, such as the fatty acid tails, and are responsible for the tendency of lipids to aggregate and form a bilayer. As lipids are added to an aqueous environment, the hydrophobic tails interact with each other through van der Waals forces, causing them to cluster together and form a bilayer structure. This is in contrast to the hydrophilic heads, which interact with the aqueous environment through hydrogen bonding and other polar interactions.
**Why Each Wrong Option is Incorrect**
**Option A:** Hydrogen bonding - While hydrogen bonding is an important force in the interaction between lipid heads and the aqueous environment, it is not the major driving force behind the formation of the lipid bilayer.
**Option B:** Electrostatic forces - Electrostatic forces, such as those between charged lipid head groups, play a role in the stability of the lipid bilayer, but they are not the primary driving force behind its formation.
**Option C:** Hydrophobic effect - While the hydrophobic effect is related to the tendency of non-polar molecules to avoid water, it is not a specific force that drives the formation of the lipid bilayer. Van der Waals interactions are the key force behind this process.
**Clinical Pearl / High-Yield Fact**
The amphipathic nature of lipids and the resulting van der Waals interactions are responsible for the formation of the lipid bilayer, which is a critical component of cellular structure and function.
**Correct Answer: C. Van der Waals interactions.**