Materials move into and out of cells through either passive transport or active transport. Passive transport includes diffusion and osmosis. Molecules tend to move from crowded to less crowded in order to achieve a balance or to reach homeostasis.

The cell membrane is selectively permeable which allows the movement of substances, especially oxygen, water, food molecules, carbon dioxide, and waste products, into or out of the cell.

passive transport – movement of molecules from a more crowded to a less crowded area WITHOUT the use of energy. Movement occurs when there are unequal concentrations of a substance inside and outside of the cell.

diffusion – movement of molecules from a region of higher concentration to a region of lower concentration.

osmosis – diffusion of water through a membrane.
active transport – movement of molecules from a less crowded to a more crowded area WITH the use of energy. Molecules are “carried” into or out of the cell using some of the cell’s energy.

Passive Transport is the process of molecules moving from a higher concentration to a lower concentration to reach equilibrium
an example would be osmosis.
-water moves through a plasma membrane
-puts the cell in 3 types of solutions
1. isotonic solution: same concentration of solutes as the cell, nothing happened
2. hypertonic solution: concentration of solutes is higher on the outside than the inside of the cell, cell shrinks
3.hypotonic solution: the solute is at a higher concentration inside the cell than outside, so water moves into the cell and it swells.

Active transport is the movement of molecules which goes against the concentration gradient (low to high) and it needs ATP.
an example would be carrier assisted transport which uses carrier proteins to move molecules against the concentration gradient, example:sodium potassium ion pump
-3 sodium ions bind to the pump, a phosphate group (from ATP) also binds to the pump
-the pump changes shape, transporting the 3 soidum ions acros the cell membrane, the sodium ions are released outsid ethe cell
-2 potassium ions (outside the cell) bind to the pump, the potassium ions are transported across the cell membrane
-the phosphate group is released and the two potassium ions are released inside the cell.

here is the SIMPLE ANSWER

passive requires no oxygen and moves from high to low concentration

active requires energy and moves from low to high concentration