What is the primary function of cardiolipin in membranes?

Cardiolipin primarily serves as a key component of mitochondrial membranes, where it plays a critical role in maintaining the structural integrity and functionality of these membranes. It is known for its unique structure, which features four fatty acid chains, contributing to the formation of lipid bilayers that stabilize membrane proteins, particularly those involved in electron transport and ATP synthesis. By anchoring these proteins within the lipid bilayer, cardiolipin helps facilitate efficient energy production through oxidative phosphorylation in mitochondria. Its presence is essential for the proper functioning of the respiratory chain complexes, which are pivotal for cellular respiration.

While the other options address aspects related to lipids, they do not accurately reflect cardiolipin's primary role. For example, energy storage is a function attributed primarily to triglycerides and phospholipids like phosphatidylcholine, while signaling lipids generally refer to specialized lipids that participate in cellular signaling pathways, such as phosphoinositides or sphingolipids. Similarly, although some membrane lipids participate in catalytic activities or are involved in biochemical reactions, this is not a primary function of cardiolipin. Therefore, cardiolipin's main purpose lies in anchoring integral membrane proteins, thereby supporting their biochemical activities within the lipid