Cell Nucleus
o The major feature distinguishing eukaryotic cells from prokaryotic cells is the nucleus of the eukaryote.
o The aqueous ‘soup’ inside the nucleus is called the nucleoplasm.
o DNA is found in the nucleus and the mitochondria in eukaryotes.
o The nucleus is wrapped in a double phospholipid bilayer (two membranes) said the nuclear envelope or membrane.
Structure of Cell Nucleus
"DNA is found in the nucleus and the mitochondria in eukaryotes"
o The nuclear envelope is perforated with large holes called nuclear pores, through which all molecules enter or leave.
o Small molecules pass right though but larger molecules (such as RNAs and proteins) can’t pass through unless they carry an appropriate sorting signal.
o RNA can exit the nucleus through the nuclear pores, but DNA cannot.
o Proteins are transported in the their fully folded form in the nuclear pore and is actively transported in via GTP hydrolysis, proteins usually have to unfold to cross the membranes of other organelles.
o Within the nucleus is an area called the nucleolus where rRNA is transcribed and the subunits of the ribosomes are assembled.
o The nucleolus is not separated from the nucleus by a membrane.
o Both the nucleus and the nucleolus disappears during prophase of mitosis and meiosis.
"Both the nucleus and the nucleolus disappears during prophase of mitosis and meiosis"
o The eukaryotic cell nucleus.
o Visible in this diagram are the ribosome-studded double membranes of the nuclear envelope, the DNA (complexed as chromatin), and the nucleolus.
o Within the cell nucleus is a viscous liquid called nucleoplasm, similar to the cytoplasm found outside the nucleus.
o Chromatin is the complex combination of DNA, RNA, and protein that makes up chromosomes.
o It is found inside the nuclei of eukaryotic cells, and within the nucleoid in prokaryotic cells.
Cell Nucleus Citations
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