3.1

Question 1

Nuclear Envelope

Answer 1

Selective barrier prevents free movement between nuclear and cytoplasm.

Maintains internal composition of nucleus.

Key role in regulation of gene expression

Contains inner and outer membrane, nuclear pore complex and nuclear lamina.

Question 2

Outer nuclear membrane

Answer 2

Ribosomes attached to surface.

Communication between nuclear intermembrane and lumen of endoplasmic reticulum.

Question 3

Inner membrane

Answer 3

Contains integral membrane proteins

Question 4

Nuclear lamina

Answer 4

Fibre network providing structural support

Made from Lamin A,B,C

Lamina are fibrous proteins 60-80kDa

Joined together to form filaments

Question 5

Formation of a Lamina

Answer 5

First association is interaction of two lamins to form a dimer, in which alpha helix areas of two polypeptides wrap around to form a coiled coil.

Dimers form filaments that form nuclear lamina.

Lamina and inner nuclear membrane interaction is facilitated by post Translational addition of lipids nd interaction with integral proteins (emerin, SUN, lamin b receptor protein)

SUN binds to KASH proteins of outer nuclear envelope forming LINC complex that connects nuclear lamina to cytoskeleton.

Lamina and inner nuclear membrane proteins interact with chromatin associated proteins.

Question 6

Nuclear pore complex

Answer 6

Octamer symmetry

Central channel of pore is where small polar molecules, ions, proteins and RNAs are transported.

In vertebrates made up of nucleoporins.