The more metabolically active a cell is, the more it's membrane contains.

When a cell is metabolically active it means there are a series of enzyme-catalysed reactions occuring in the cell (metabollic pathway) that determine the nutrients to be used for production of energy. The more metabolically active a  cell is the more proteins its membrane contain while the less active a cell is the more fats its membrane contains.

Are you asking about a street map usage  if so here is your answer  a street map for a very limited area could simply be a bit map or a .jpg image.  but a more general map would probably store the streets as vectors.  but you shouldn't assume that there is one way to do it