you only need to escape the cell body (which just means going far enough from the center, requiring to somehow pass the cell walls (membrane)).
One way is to explode the cell core (nucleus) by overfeeding it (hint: 'centrioles' have more calories). When the core booms the shockwave dissolves the walls for a few seconds, giving you a brief chance to escape.
Another way is to actively dissolve the cell walls by getting them in touch with the blue organells ('vesicles'). They 'eat' the wall membrane, with the tradeoff this usually takes a bit longer than the exploding-strategy.
(I found this can be a bit tedious though, so instead "wall damage on collision" might improve the gameplay? Also after victory/fail the game just returns to main menu, maybe a score would help, too?^^)