Describe how osmosis and active transport differ as methods of moving substances across a cell membrane. Include in your answer what is meant by osmosis, what is meant by active transport, and how the two processes differ.

Osmosis is the movement of water molecules across a selectively permeable membrane.
It occurs from a region of higher water concentration to a region of lower water concentration, i.e. down a concentration gradient.
Osmosis is a passive process and does not require energy.
Active transport is the movement of substances across a membrane against a concentration gradient, i.e. from a region of lower concentration to a region of higher concentration.
Active transport requires energy, usually from respiration (ATP), whereas osmosis does not.