The lipids that form the main structural component of cell membranes are __________.

• A. triacylglycerols
• B. proteins
• C. cholesterol
• D. carbohydrates
• E. phospholipids

Answer: (E)

Verified step by step guidance

1. Understand the structure of cell membranes: Cell membranes are primarily composed of a bilayer of lipids, which provides a flexible matrix and barrier to the passage of ions and molecules.
2. Identify the main type of lipid in cell membranes: The primary lipids that form the structural component of cell membranes are phospholipids.
3. Recognize the structure of phospholipids: Phospholipids have a hydrophilic (water-attracting) 'head' and two hydrophobic (water-repelling) 'tails'. This amphipathic nature allows them to form bilayers in aqueous environments.
4. Differentiate phospholipids from other lipids: Triacylglycerols are fats used for energy storage, not structural components of membranes. Cholesterol is present in membranes but serves to modulate fluidity, not as a primary structural component. Carbohydrates are not lipids and are involved in cell recognition and signaling.
5. Conclude that phospholipids are the correct answer: Given their unique structure and role in forming the bilayer, phospholipids are the main structural component of cell membranes.