anode

Meaning: The anode is the electrode at which a species loses electrons (is oxidized). Electrons flow through the wire from the anode to the cathode, where reduction occurs. Anions migrate toward the anode through the solution or salt bridge, and the anode's metal may dissolve (it loses mass) if the metal itself is oxidized.

In a galvanic (voltaic) cell, the reaction is spontaneous, so the anode is the negative terminal. In an electrolytic cell, an external power source drives a nonspontaneous reaction, so the anode is connected to the positive terminal of the source and is the positive electrode. Oxidation still occurs there.

On the MCAT: A passage gives a cell diagram or half-reactions with standard reduction potentials. You identify the anode as the half-cell with the lower (more negative) E°red in a galvanic cell, then predict electron flow, direction of ion movement, and which electrode gains or loses mass. In a cell notation such as Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s), the anode is written on the left.

Common confusion: Students memorize "anode is negative" and apply it to every cell. The sign flips between galvanic and electrolytic cells, but the definition does not. Use the mnemonic "An Ox" (anode, oxidation) and "Red Cat" (reduction, cathode). Oxidation at the anode settles it every time.