Which type of lipid is responsible for maintaining cell membrane rigidity?

• A. Phospholipids
• B. Triglycerides
• C. Steroids
• D. Wax

Answer: (C)

Steroids play a crucial role in maintaining the rigidity and fluidity of cell membranes. Cholesterol, a type of steroid, is particularly significant in this regard. It is interspersed within the phospholipid bilayer of cell membranes. The presence of cholesterol molecules helps stabilize the membrane, preventing it from becoming too fluid at higher temperatures and too rigid at lower temperatures. This balance is essential for proper cellular function, as it allows for the membrane to remain flexible while also maintaining its integrity and barrier properties.

Phospholipids form the fundamental structure of the membrane but do not provide the same level of rigidity. Triglycerides mainly serve as energy storage molecules and are not a primary component of cell membranes. Waxes, on the other hand, are typically found in structures that require waterproofing rather than providing rigidity to cell membranes. Thus, cholesterol and other steroids are specifically designed to provide the necessary structural support for cell membrane functionality.