Can all molecules diffuse through all cell membranes explain

No, some molecules are too large to fit through the pores of the cellular membrane. The cellular membrane is "semi-permeable", meaning that it lets only certain substances cross the membrane. This is determined by the size of the substance, the type of charge, and the lipid solubility of the substances.

B.) nitrogen fixationnitrogen fixation is the process of nitrogen molecules seeping into the soil and inside plant roots and bacteria. it gives more "life" to plants