Julie has been working in the laboratory with a new antibiotic. First, she placed an antibiotic on a petri dish of bacteria. Then she placed a solution of distilled water in the petri dish and observed under the microscope that water moves into the bacterial cells, causing them to burst. In the control group of bacteria that do not receive the antibiotic, the cells do not swell or burst. Julie is trying to determine what organelle is damaged, and preventing homeostasis?.