The negative control of this experiment is presented in lane 7. In this lane a lower, faint band is observed. Since we only used a secondary antibody in this lane and not a specific primary antibody, this band has to be a result of a non-specific interaction between the secondary antibodies and one of the proteins of the Paramecium. Therefore, this band is not indicative of the presence of the protein pumps.
 
Legend
Lanes 1, 8  Size marker (kilo Daltons)
Lane  2      Purified protein pump
Lane  3      Lysate of the whole Paramecium
Lane  4      Lysate of the Parameciun food vacuole collected 0.5 min after feeding.
Lane  5      Lysate of the Parameciun food vacuole collected 5 min after feeding.
Lane  6      Lysate of the Parameciun food vacuole collected 10 min after feeding.
Lane  7      Lysate of the whole Paramecium reacted only with the secondary antibody.

Now, that we understand the meaning and importance of a positive and a negative control, let us examine the lysate derived from whole Paramecium (lane 3).

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