Final answer:
Statement B is true, as phosphoglycerides, sphingolipids, and sterols are the major lipid molecules in cell membranes. Phospholipids form a bilayer with hydrophilic heads and hydrophobic tails. Sphingolipids and sterols also play vital roles in membrane structure and function.
Step-by-step explanation:
The student's question pertains to the lipid components of biomembranes. Among the options provided, statement B is true. Phosphoglycerides, sphingolipids, and sterols are indeed the major lipid molecules found in membranes. These lipids are crucial for forming the lipid bilayer, which is fundamental to membrane structure and function. Phospholipids, the main type of phosphoglycerides, are composed of two fatty acid chains and a phosphate group attached to a glycerol backbone.
This structure results in a hydrophilic head and two hydrophobic tails, allowing phospholipids to form the bilayer of cell membranes, with the tails facing inward, away from water, and the heads facing the aqueous environment inside and outside the cell. Sphingolipids are similar to phospholipids but have a sphingosine backbone instead of glycerol. Sterols, such as cholesterol, are another crucial component, providing rigidity and fluidity to the membrane. The lipid bilayer acts as a barrier to most polar substances while allowing for the specific transport of molecules vital to cellular function.