What structure supports all life forms, though it is invisible to the naked eye and primarily made of cells?

Category: Science · Difficulty: hard

Hint: It regulates what enters and leaves the cell.

Answer

Cell structures

Explanation

The cell membrane is a barrier that protects the cell and controls the movement of substances in and out.

This is a hard science riddle — a tricky one that takes a little thought. The answer is Cell structures.

More Science riddles

All Science riddles · Riddles with answers · Home