AP BIOLOGY

Detailed explanation-1: -Nuclear pores, small channels that span the nuclear envelope, let substances enter and exit the nucleus. Each pore is lined by a set of proteins, called the nuclear pore complex, that control what molecules can go in or out.

Detailed explanation-2: -The nucleus has our DNA that contains all our genetic information. The DNA is found on structures in the nucleus called chromosomes. There are 23 pairs (46 total) of chromosomes in each nucleus of each cell. The nucleus is surrounded by a nuclear membrane, which controls what goes in and out.

Detailed explanation-3: -The critical function of the nuclear membranes is to act as a barrier that separates the contents of the nucleus from the cytoplasm. Like other cell membranes, the nuclear membranes are phospholipid bilayers, which are permeable only to small nonpolar molecules (see Figure 2.49).

Detailed explanation-4: -The Cellular Membrane The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells.