What would be the major disadvantage for human cells to cell walls?

If they have cell walls it will be hard for the material to get in and out of the cell resulting in cell death or damage

Eukaryotic cells are theorized to have evolved from prokaryotes called the endosymbiotic theory. this explains that the most primitive eukaryotic cell engulfed a prokaryotic cell (by the process of phagocytosis) that is capable of cellular respiration and another prokaryotic cell that is capable of photosynthesis. these prokaryotic cells eventually became organelles and these organelles are the mitochondria and the chloroplast