The venom of black widow spiders (Latrodectus mactans) contains an enzyme that hydrolyzes lecithin to the phospholipid lysolecit
hin. The lysolecithin lyses red blood cells, destroying them. One possible mechanism whereby lysolecithin disrupts the plasma membranes of red blood cells is that it: A. may act in a manner similar to detergents.
B. is toxic to red blood cells.
C. acts as a second messenger to stimulate apoptosis.
D. binds calcium ions, compromising membrane integrity.
Partial hydrolysis of lecithin by lecithinases (enzyme in black widow spiders and snakes venom) causes the removal of only one fatty acid to yield lysolecithins, which when subjected to the bloodstream by sting as a result of spider bite causes the rupture of red blood cells.
Thus, the mechanism is that it is toxic to red blood cells.
A postsynaptic potential is defined as excitatory if it makes it easier for the neuron to fire an action potential. ... A postsynaptic potential is considered inhibitory when the resulting change in membrane voltage makes it more difficult for the cell to fire an action potential, lowering the firing rate of the neuron.
