The Cell

function of the nucleus (found only in eukaryotic cells) is simply to keep the huge expanse of DNA in one place.

nucleus has a phospholipid bilayer membrane of its own, just like the cell’s main membrane. And, of course, it lets things in and out, just as the cell’s membrane does.

Around certain sections of DNA inside the nucleus is a dense crowding of molecules that constantly produce new ribosomes, the molecular machines that actually build the proteins.

Schematic diagram of a section of DNA. The green twisting section represents the sugar-phosphate backbone, and the rungs are the nucleobases. A (purple) always bonds with T (orange), and C (yellow) with G (pink).

eukaryotic cells (and in archaea), the DNA is wrapped every so often along its length around blobs of a protein called histones; the result looks like beads (histones) on a string (DNA). The beaded string is further wrapped around itself, so that it becomes a much fatter string

a protein is to be made, enzymes unpack and unwind the section of the DNA containing the relevant gene, so that the code becomes exposed.

end, with eight histone molecules at its core, is called a nucleosome

first two stages in the process of protein building are copying out the recipe and taking it outside the nucleus.

(ribonucleic acid), a compound very similar to DNA (deoxyribonucleic acid) but single-stranded.

RNA is copied from the complementary strand of DNA, not the coding strand.