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.