This study aims at providing some fundamental and quantitative answers to the questions why and how the widely used low-energy heavy ions such as Ar ions at 20-30 keV, which have the ranges in the order of 10 nm in water, can penetrate a cell wall having a thickness in the order of 10² nm and introduce large exogenous molecules into the cells. The experiment focused on 20-30-keV Ar-ion implantation in various plant tissued and bacteria E.coli strain DH5a to the doses ranging from 10¹⁴ - 10¹⁶ ions/cm². Auxiliary 15-30-keV N-ion implantation in the plant tissues was also carried out. The effects of ion beam irradiation on tissue outer cell structure and the ability of transfering large exogenous molecules of Trypan blue (TB) and plasmid DNA, pGEM2, were investigated. Analysis of the simulations of the ion implantation processes indicates that the cell wall made of cellulose microfibrils as a porous structure is a semirigid material so that Ar ions at certain low energies can increase permeability of the cell wall resulting in exogenous macromolecule transferring. This has been supported by an experimental evidence that the 20-ke V Ar-ion implantation only results in retaining of the TB dye in the cell wall whereas the 30-ke V Ar-ion implantation can allow the dye to enter the cell and the 25-ke V Ar-ion beam can result in introducing and expressing of pGEM2 in E.coli.