[Answer] Extracellular toxins act on the cell surface by:

Answer: binding to certain receptors and forming pores in the cytoplasmic membrane
Extracellular toxins act on the cell surface by:
Abstract. AB toxins consist of an enzymatic A subunit and a cell-binding B subunit (1). These toxins are secreted into the extracellular milieu but they act upon targets within the eukaryotic cytosol. Some AB toxins travel by vesicle carriers from the cell surface to the endoplasmic reticulum (ER) before entering the cytosol (2-4).
Certain bacterial and plant toxins have the unusual ability to catalyze chemical reactions inside animal cells. Such toxins are always composed of two functionally distinct parts termed A and B and they are often called A-B toxins . The B part binds to receptor molecules on the animal cell surface and positions the toxin upon the cell membrane.
the cell dies or the cell membrane ruptures the toxins are released into the water ( extracellular toxins ). However in other species cylindrospermopsin for example a significant amount of the toxin may be naturally released to the water by the live cyanobacterial cell ; the reported ratio is about 50% intracellular and 50% extracellular .
G-protein-linked receptors form the largest family of cell – surface receptors and are found in all eucaryotes. About 5% of the genes in the nematode C. elegans for example encode such receptors and thousands have already been defined i…

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