The impact craters on the moon are created by collisions made by other asteroids many thousands of years ago
All elements are made of atoms
This statement is true. Only active transport can move molecules up a concentration gradient using energy. Passive transport on the other hand, uses no energy and occurs naturally. Therefore molecules can only move a concentration gradient.
Answer:
O To prevent certain ions and molecules from entering or exiting the celI.
Explanation:
The cell needs to keep a constant chemical composition on the inside in order to mantain homeostasis
