Which macromolecule forms a double layer as the primary structure of cell membranes?

Phospholipids

Explanation:

The phospholipids are located in the plasma membrane and are main part of the membrane. The hydrophobiticity of membrane is only due to presence of phospholipids. The hydrophobic portion in the membrane allows delivery of drugs because most of the drugs are non-polar and can easily cross the cell membrane.

Thus, phospholipids forms a double layer as the primary structure of cell membranes.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

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