Nuclear activity in your body!! REAL
Each of your cells (erythrocyte or red blood cells aside) contains a nucleus or, sometimes, multiple nucleii as is the case for muscle cells, placenta cells and hepatocytes. The nucleus is about 1/10th of the cell's size, standing at an average of 6 micrometers.
Look at this star...
It is easy to spot due to its size and double-enveloppe with holes--pores-- that is contiguous with the Rough Endoplasmic Rediculum (RER), both of which are covered in ribosomes.
The presence of a nucleus is, along with other cellular compartiments or organelles, the main difference between eukaryotic cells and prokaryotic cells. Genetic information is found in the nucleus, it is what we call genome. In eukaryotic cells, genetic information takes the form of several chromosomes whereas procaryotic cells have floating circular DNA, 1 chromosome and plasmid(s). But we'll focus on eukaryotic cells here.
The nucleoplasm, the gelatinous content of the nucleus, contains chromatin that is made of chains of nucleosomes (a unit of 4 histone proteins woven into DNA strands like beads on a string) in two forms:
Heterochromatin (width: 30nm), the very condensed version that pools at the borders of the nucleus, away from the nucleolus. Genes are silent in heterochromatin. Due to how tight it is, it does not allow expression.
and...
Euchromatin (width: 11nm), the relaxed version, loose enough that DNA can be read and transcribed into RNA.
Why make RNA and ribosomes?
Together, ribosomes with r RNA and the two other types of RNA allow the cell to make proteins based on genetic information, reading DNA. And proteins do.. everything.
The nucleolus is where r RNA (ribosomic RNA) is associated to ribosomic proteins in order to make ribosomes. r RNA makes up 80% of cellular RNA.
In the nucleus are also synthetized t RNA (transfer RNA) by RNA Polymerase III and m RNA (messenger RNA) by RNA Polymerase II. Messenger RNA holds the information that will be read or translated for protein synthesis in the Rough Endoplasmic Reticulum.
But not yet! It needs to undergo maturation by splicing: introns--which do not code--are removed from pre-mRNA and only introns (coding for proteins) remain.
From there, transfer RNA's ending, its 3-nucleotide anticodon, is affixed to mRNA so it can check that mRNA codons are coding for the right amino acids for the corresponding protein.
Transfer RNA reads mRNA and check its information accuracy. It is called 'transfer' because it is also responsible for transportation of amino acids to ribosomes whose rRNA work on assembling amino acids based on the 'message' of mRNA.
This entire process is how proteins are made, by translation of DNA.
Most of protein synthesis occurs in the rough endoplasmic reticulum. (here ↓)
Soon enough they'll undergo post-translational modifications...
