1. 4.4 The Cell Nucleus
Section 4.4

2. Learning Objectives
Compare & contrast the structure of prokaryotic cells & eukaryotic cells
Relate the structure of the nucleus to its function as the control center of the eukaryotic cell
Identify the parts that make up the structure of the nucleus & describe their function
Identify organelles produced in the nucleus & their function

3. Eukaryotic Cells All start life with a nucleus
Nucleus = double membrane organelle that contains a eukaryotic cell’s DNA
Nucleoplasm = jellylike area inside nucleus
Have organelles that are membrane-bound
Made of membrane layers
Cytosol = the fluid part of the cytoplasm
Cytoplasm is technically the cytosol and the organelles of the cell (except for the nucleus

4. DNA In Eukaryotic Cells
DNA is in long threadlike (strings) pieces
Not circular like prokaryotic cells have
Has genes
Genes = areas of DNA that contains instructions for making proteins and RNA molecules

6. Chromatin = DNA wrapped around histones
Histones = proteins that DNA wraps around
Chromatin looks like a messy area of string in a microscope
Chromosome = coiled DNA pieces visible when a cell is dividing
Look like Xs

7. Nucleus Stores the DNA Is created by the nuclear envelope
Nuclear envelope = a double membrane that separates the nucleoplasm from the cytoplasm
Nuclear pores = holes or openings in the nuclear envelope
Controls what large molecules enter and leave the nucleus

9. Nucleolus
Nucleolus = dense area inside the nucleus where RNA & ribosomes are made
Cells can have one or more nucleoli

10. Ribosomes Made in the nucleolus
Made up of a large subunit & a small subunit
Can be found in free-floating in the cytoplasm (free ribosomes) or attached to ER membranes (bound ribosomes)
Make proteins for the cell
Cells can change how many ribosomes they have in order to meet its metabolic needs