IB Biology Exam Prep

Answer: D, Cell wall. Plant cells are surrounded by both a cell membrane and a thick outer cell wall, while animal cells are only surrounded by a cell membrane.

Key Takeaway: Plant cells and animal cells are strikingly similar in terms of content. Since plant cells have a rigid wall, they take more of a rectangular shape, whereas animal cells are generally round. Other key differences between plant cells and animal cells are the presence of the chloroplast in plant cells and the presence of the centriole in animal cells.