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.

a

explanation:

many plants naturally reproduce this way, but it can also be induced artificially. horticulturalists have developed asexual propagation techniques that use vegetative plant parts to replicate plants. success rates and difficulty of propagation vary greatly. monocotyledons typically lack a vascular cambium and therefore are harder to propagate.