Animal cells are typical of the eukaryotic cell, enclosed by a plasma membrane and containing a membrane-bound nucleus and organelles. ... The ability to move about by the use of specialized muscle tissues is a hallmark of the animal world, though a few animals, primarily sponges, do not possess differentiated tissues.

Why this membrane is for an animal cell?

This membrane performs two vital functions: it creates the outer boundary of the cell and keeps the cell together, and it controls entry and exit of material from the cell. The animal cell membrane is capable of performing this second task because of proteins embedded within it.

Why are typical animal cells rarely larger than 0.1 mm in diameter?

As cells grow larger than 10 microns, they have to bolster their contents against gravity. But if cells stay under that 10-micron threshold—as the vast majority of animal cells do—they can essentially escape gravity's forces. The building blocks of life are small, essentially, because gravity keeps them that way.