<strong>Nuclear Pores:</strong> Nuclear membrane or nuclear envelope is not a continuous layer but innumerable microscopic pores are found in it. These pores are called. nuclear pores. These holes are distributed in a row, <strong>hexagonal or randomly.</strong> Each nuclear pore is surrounded by a <strong>ring-like annulus</strong>. Annulus protein is made of amorphous material of nature and is spread between the cytoplasm located on the outside and the nuclear fluid (nucleoplasm) located on the inside. The nuclear pore ring is collectively called the pore complex. <br><strong>Function:</strong> Many substances like proteins and RNA etc. come and go into the nucleus and cytoplasm through the nuclear pores. This process of exchange is selected or controlled and only particles with specific molecular weight are allowed to exchange. Thus, the nuclear envelope acts as a barrier level for the molecules of many substances and also for micro ions K+, Na+ and Cl- and does not allow free exchange. Thus, necessary gap is maintained in their pH.