The Space External to the Outermost Structure of a Cell. For Cells Without External Protective or External Encapsulating Structures This Refers to Space Outside of the Plasma Membrane. This Term Covers the Host Cell Environment Outside an Intracellular Parasite.
A Presynaptic Membrane That Is Part of Another Organism I.e. a Secondary Organism with Which the First Organism Is Interacting. a Presynaptic Membrane Is Specialized Area of Membrane of the Axon Terminal That Faces the Plasma Membrane of the Neuron or Muscle Fiber with Which the Axon Terminal Establishes a Synaptic Junction; Many Synaptic Junctions Exhibit Structural Presynaptic Characteristics Such As Conical Electron Dense Internal Protrusions That Distinguish It From the Remainder of the Axon Plasma Membrane.