This macromolecule may function as a long-term energy source, insulation and waterproof protection.

Lipid is the macro molecule which may function as a long-term energy source, insulation and water proof protection.

Explanation:

Lipids are macro molecules that are  made out of hydrogen, carbon, and oxygen. They have more carbon-hydrogen bonding and less oxygen atoms. Numerous lipids are comprised of a glycerol particle joined with three unsaturated fats.

Unsaturated fats are long chains of carbon, hydrogen, and oxygen. Lipids are highly insoluble in water. Due to such type of structural arrangements the lipids functions as long term energy source, insulating material and also as waterproof element to the plants and animals.