Final answer:
Phospholipids and steroids compose the cell membrane bilayer, with cholesterol playing a crucial role in maintaining membrane fluidity.
Explanation:
Phospholipids and steroids are the types of lipids that make up the bilayer forming cell membranes. Phospholipids have a glycerol or sphingosine backbone with two fatty acid chains and a phosphate-containing group, while steroids have a basic structure of four fused carbon rings, with cholesterol being a vital component of the plasma membrane.Cholesterol helps maintain the fluid nature of the membrane by regulating its flexibility and structure.
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