LIFE SCIENCE

Detailed explanation-1: -The inner and outer nuclear membranes are joined at nuclear pore complexes, the sole channels through which small polar molecules and macromolecules are able to travel through the nuclear envelope (Figure 8.2).

Detailed explanation-2: -Nuclear pores The nuclear envelope is punctured by around a thousand nuclear pore complexes, about 100 nm across, with an inner channel about 40 nm wide. The complexes contain a number of nucleoporins, proteins that link the inner and outer nuclear membranes.