Answer:
a) Chemical Z is a large, polar molecule, and it can move across the plasma membrane without the input of cellular energy through a process called passive diffusion. In this process, the molecule moves from an area of high concentration to an area of low concentration, crossing the plasma membrane through special protein channels, known as transport proteins. The amount of DNA in a cell indicates whether the cell is in G1, S, or G2 because these phases of the cell cycle are characterized by changes in DNA content. G1 phase is when the cell grows and prepares for DNA replication, S phase is where DNA replication occurs, and G2 phase is when the cell prepares for division.
b) The dependent variable in the experiment is the percentage of cells in each phase of interphase (G1, S, or G2) after treatment with different chemicals. Untreated cells are used in the experiment to serve as a control group, allowing for comparison against the treated cells and helping to determine the specific effects of the chemicals. Chemicals B and C are used in the experiment to investigate their effects on cell cycle progression and to compare their effects with the effects of Chemical Z.
c) Based on the data in Figure 2, it appears that chemical Z treatment blocks the cell cycle at the G1 phase of interphase. This is supported by the significant increase in the percentage of cells in G1 phase compared to the untreated sample. The trend in the data shows a substantial increase in the percentage of cells in G1 phase after treatment with chemical Z.
d) The null hypothesis for the experiment on cancerous T cells would be: "Chemical Z does not block the cell cycle of cancerous T cells." When comparing the effects of chemical Z on cancerous T cells and normal cells, the null hypothesis assumes that there is no effect of chemical Z on cancerous T cells' cell cycle. Regarding the negative effect of using chemical Z on a patient's ability to fight off an infection, this could be justified by the fact that T cells are critical components of the immune system, and any disruption to their cell cycle may impair the body's ability to mount an effective immune response against pathogens. Additionally, if T cells are prevented from dividing or responding to pathogens due to the blocking of their cell cycle by chemical Z, it could compromise the body's defense against infections.