These macromolecules are polar [polar: having different ends] because they are formed by head to tail condensation of polar monomers. Let's look at the three major classes of macromolecules to see how this works, and let's begin with carbohydrates.
Bostwick Steel Lath Company advertisement for steel truss loop type metal lath in 1920. A lath or slat is a thin, narrow strip of straight-grained wood used under roof shingles or tiles, on lath and plaster walls and ceilings to hold plaster, and in lattice and trellis work.
-200 mesh magnalium, mixed with turnings. A 50:50 alloy of magnesium and aluminum commonly used as a metal fuel, for spark effects, colored stars, strobe compositions and in crackling stars. NOTE: Each container consists of .49 lb. of magnesium-aluminum powder containing .51 lb. of magnesium turnings.