Lecture 4 - Nucleus

BIOL10110

what are the 3 main functions of the nucleus?

1. Storage +maintenance of cell’s genetic info

2. control of gene expression [transcription]

3. regulation of protein synthesis

What is the structure of the nuclear envelope?

two lipid bilayer membrane

> inner nuclear membrane

> outer nuclear membrane

there is perinuclear spec between (10-5nm wide)

^{what is the function of the nuclear pores>?}

allow materials to move between cytosol + nucleus

what is the structure of the nuclear lamina?

formed by intermediate filament proteins on inner face of INM

what is the function of the nuclear lamina?

gives structural support to nucleus

anchors interphase chromatin

what is the structure of nuclear pores?

protein channels

inner + outer membranes fused together

what is the function of nuclear pores?

bidirectional transit of materials between nucleus + cytoplasm

assembled ribosomal proteins, RNA exit the nucleus

proteins, carbohydrates, signalling molecules, lipids enter nucleus

what is the average # nuclear pores in a cell?

3000

what are the units DNA is organised into?

chromosomes

What is the DNA-protein complex called?

chromatin

What is chromatin?

material that makes up a chromosomes consisting of DNA and protein

what are the proteins in chromatin called?

Histones

What do the chromatin do?

condense DNA by wrapping + re-wrapping DNA in very tight coil

What is the nucleosome

a segment of DNA wrapped around 8 histone proteins

• 2 copies of H2A, H2B, H3, H4

what does it mean when chromatin is less condensed?

the genes are expressed - Euchromatin

What does it mean hen the DNA is more condensed

silent gene or no genes - heterochromatin

what is the nucleolus the site of?

• ribosomal RNA (rRNA) synthesis

• rRNA processing

• Assembly of ribosomal subunits

What are the 2 types of ribosomes?

1. free in cytoplasm

2. bound to ER

What happens to proteins made in free ribosomes?

function in cytoplasm

What happens to proteins made in bounded ribosomes?

insertion into membranes + organelles

OR

secretion