lecture 10 - cell nucleus Flashcards
What is the typical size of the nucleus?
5-10 micrometres
What surrounds the nucleus?
Nuclear envelope
How many membranes are in the nuclear envelope?
2
What is the space between the 2 membranes of the nuclear envelope?
The perinuclear space
What is the outer membrane of the nuclear envelope continuous with?
the rough Endoplasmic Reticulum
What is the perinuclear space continuous with?
the lumen of the rER
What is the function of the nuclear pore complex?
Controls movement in and out of the nucleus.
What is transferred out of the nucleus via the nuclear pore complex?
mRNA, tRNA, ribosomal subunits, macromolecules
What is transferred into the cell via the nuclear pore complex?
Control signals, RNA building blocks, energy
What is the function of the control signals in the nucleus?
They control when genes are turned ‘off’ or ‘on.’
What is the inner surface of the nuclear envelope?
Nuclear lamina
What is the structure of the nuclear lamina?
Made up of intermediate filaments, consisting of the protein lamin
What are the two key functions of the nuclear lamina?
Maintain nucleus shape, organise DNA packing
What is the nucleolus?
A structure that sits inside the nucleus of a cell and makes ribosomal RNA, which can combine with proteins to produce ribosomes.
What is the diameter of a DNA double helix strand?
2nm
What histones are used to form nucleosomes?
H2-H4
What is a nucleosome and how are they formed?
A ‘bead’ consisting on eight histones clustered around part of the DNA strand. 10nm wide
How are 30nm DNA fibres formed?
10nm nucleosomes interact with H1 histones, to form coils with a 30nm diameter.
What is chromatin?
A 300nm diameter fibre made up of loops of 30nm fibre.
What happens to chromatin fibres during the metaphase of cell division?
They form chromosomes.
What is a karyotype?
A representation of the chromosomes of each cell, which are normally arranged randomly within the cell.
What are the less dense areas of the nucleus?
Euchromatin
What are the dense areas of the nucleus?
Heterochromatin
What is the function of euchromatin?
Allow genes currently being used to be easily accessible, by packing DNA less densely.
What is the function of the heterochromatin?
Genes that are not currently in use are packed tightly so they are inaccessible.
How can the relationship between euchromatin and heterochromatin be described?
Dynamic
