Protoplasm

Protoplasm was part of a cell. According to the Fifth Doctor, it was "the basic form of human life" from billions of years before Tegan Jovanka's time, from which humans evolved. (AUDIO: Interstitial)

The process used by the Chameleons to assume the identities of humans involved the use of armband-like devices placed on both subjects. If an armband was removed from the original, the Chameleon that assumed their identity would be killed, reduced to a small blob of protoplasm. (TV: The Faceless Ones)

The Saiph were able to turn into protoplasm. (AUDIO: The Stealers from Saiph)

Because computers were unable to withstand the reality-changing stress, TARDISes required morphologically unstable living organic matter, or protoplasm, for their Block Transfer Computations. (PROSE: Cat's Cradle: Witch Mark)