What is (are) the main difference(s) between passive transport and active transport? group of answer choices passive transport does not require any cellular proteins; active transport requires cellular proteins. active transport works against gravity (for example, upwards from the roots of a tree); passive transport works with gravity (downward). passive transport occurs primarily in single-cell organisms; active transport occurs primarily in multi-cellular organisms. active transport requires cellular energy for substances to cross the cell membrane; passive transport does not.