The part of the bacterial cell most involved in Gram staining is the cell wall.

Here's why:

* Gram-positive bacteria have a thick peptidoglycan layer in their cell wall. This layer traps the crystal violet dye during the staining process, which then forms a complex with iodine. This complex is large and difficult to remove with alcohol, resulting in the bacteria remaining purple.

* Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane containing lipopolysaccharide (LPS). The alcohol used in the staining process dissolves the outer membrane and washes away the crystal violet-iodine complex, leaving the bacteria colorless. They then take up the counterstain (safranin), appearing pink.

Therefore, the differences in the structure and composition of the cell wall are the key determinants of Gram staining results.