Eukaryote Cell Nucleus : BIOL 107

Lec 13

importance

defining part of Eukaryote cells

composition of nucleus

are made of membranes and hold the chromosomes

function in general

import/ export molecules

function 1

synthesize mRNA

function 2

synthesize tRNA

function 3

synthesize ribosomes

Chromosome structure

long, linear molecule // 23 pairs

How long are chromosomes

6400 Mb

Centromere function

hold sister chromatids together

chromatin

things inside nucleus

Euchromatin function

synthesize mRNA and tRNA

Euchromatin location

light, middle of nucleus

Heterochromatin function

Centromere DNA storage

Heterochromatin location

dark, edges of nucleus

Nucleolus function

rRNA synthesis

Nucleolus location

dark, round, middle of nucleus

Nuclear envelope membrane function

separates nucleus from cytosol

Nuclear envelope membrane structure

2 phospholipid bilayer and fluid filled space

Nuclear lamina function

gives nucleus its round shape

Nuclear lamina structure

intermediate filaments

Nuclear pores structure

large protein cylinders // “molecular machines”

Nuclear pores function

import and export

Why do some mature Eukaryotic cells don't have a nucleus

eg. RBC expel the nucleus during maturation

Why is the nucleus considered to be an organelle?

because it has a specialized structure that performs a specific function (they are also membrane bound)

Why are nuclear pores and ribosomes considered to be molecular machines rather than organelles?

they are not technically “membrane bound” and they lack a defined structure

What exits the nucleus?

tRNA, mRNA, ribosomes

What enters the nucleus?

DNA polymermase, nucleotides, RNA polymerase, and ribosomal proteins