In Paramecium Lab Report

Exocytosis Lab Report Rough Draft

Abstract: In Paramecium caudatum, trichocysts are 10^3 secretory vesicles that are released from the cytoplasm. We first observed how the presence of Alcian blue dye triggers normal secretion of trichocysts, and we then tested four different hypotheses in order to determine how the presence of Ca++ ions in the extracellular and intracellular environment affects the secretion of trichocysts. Our first our hypothesis tested whether extracellular calcium is required for the secretion of trichocysts by treating cells with EGTA, an agent that blocks calcium ions; our second tested whether increased calcium will counter the inhibitory effects of EGTA; our third tested whether adding different ion, like MgCl,
Trichocysts are secreted from the cell as a defense mechanism when certain stimuli are introduced into the extracellular environment. The secretion of trichocysts is controlled by the presence of Ca++ ions within the plasma membrane and in the extracellular environment. The purpose of our experiment was to observe the extent to which exocytosis is dependant on the presence of extracellular and intracellular calcium ions, and to determine if other extracellular ions can have the same effect as calcium. The cells were first treated with 0.03% Alcian blue dye, which triggers normal exocytosis. Cells were then treated with EGTA, an agent that inhibits calcium, in order to observe how trichocyst secretion is affected when calcium ions are sequestered. Additional calcium ions were added to the extracellular environment to determine if the effects of EGTA could be countered by increasing calcium. The cells were then exposed to a different ion, MgCl, to observe if a different ion could have the same promoting effect in the extracellular environment as calcium. Finally, the effect of intracellular calcium was tested by treating cells with a calcium ionophore (A23187) and caffeine, which both stimulate the processing of calcium into the cytoplasm of a
We determined that calcium ions in the extracellular environment promote the secretion of trichocysts, but that secretion can still take place even when an inhibitory agent like EGTA is introduced. Adding additional calcium ions into the extracellular environment does not counteract the inhibitory effects of EGTA. Introducing a different ion like MgCl has a similar effect but less pronounced effect as calcium ions. We also found that introducing certain agents that stimulate the release of intracellular calcium, like caffeine, greatly increases the secretion of trichocysts. The other agent we tested, calcium ionophore, had no effect on the secretion of trichocysts. Our data substantiate our expectation that intracellular calcium ions promote and control the secretion of