Secondary endosymbiosis, illustration. Secondary endosymbiosis is a process by which a heterotrophic eukaryotic cell, a cell that has membrane-bound organelles that cannot produce its own food, engulfs a photosynthetic eukaryotic cell, a cell that has membrane-bound organelles that produce food from sunlight. During the engulfing process the engulfed cell becomes surrounded by it's host's membrane, resulting in it having four membranes. Organelles that are no longer needed by the engulfed cell degenerate, meaning that it cannot escape and live independently. For this image without text see F034/7293.