The Endomembrane SystemDo Now: 11/9

Take out homework

What are the 4 levels of protein structure?

General Cell Terminology

• Everything between the nucleus and the cell membrane is called CYTOPLASM.

• CYTOPLASM is:– All of the organelles like

mitochondria, etc.– The CYTOSOL, which is

the aqueous solution everything else floats around in

The nucleus is a small sphere that holds all of a cell’s DNA.

I. The Nucleus

The nucleus is surrounded by a lipid membrane called the nuclear envelope, which is very similar

to the cell membrane. It has

openings called nuclear pores that allow things in and out of the nucleus.

Most of the inside of a nucleus is made up of chromatin, which is a mix of DNA and certain proteins.

The nucleolus is a small dark part inside a nucleus where ribosomes are

made.

II. The Endomembrane system• The endomembrane system is a series of

folded lipid membranes where protein production takes place. It includes:– The nuclear envelope– The rough and smooth endoplasmic reticulum– The Golgi bodies– vesicles

• PROKARYOTES have NO INTERNAL MEMBRANES. Protein production occurs in the cytoplasm

The Endoplasmic Reticulum

• Structure: The endoplasmic reticulum is a large series of folded membranes attached to the outside of the nucleus.

• Function: Nucleic acids and proteins travel through the tubes and folds during the process of protein production.

Two Parts of the ER

• The first part has RIBOSOMES attached to it, and is therefore called the ROUGH endoplasmic reticulum

• The second part has no ribosomes and is called the SMOOTH ER.

About those SUPER IMPORTANT ribosomes…

• Very important function:

RIBOSOMES MAKE PROTEINS!

Structure:

Two pieces of RNA stuck together

More on Ribosomes in the Future…

• We’ll learn more about how ribosomes make proteins when we study molecular genetics. The ribiosome basics:– Made of rRNA; – thousands per cell.– Use the information in mRNA to build a

polypeptide from amino acids.– Found in all cell types.

Do Now 11/29: Protein Production• Copy and complete the list of the steps eukaryotic cells go

through to make protein, including the organelles involved. (use flowchart!). NOTE: Leave 5-7 blank for now.

1. DNA in the nucleus stores instructions for building proteins.

2.

3.

4. Lipids and other substances are produced in the smooth ER.

5.

6.

7.

8. Active proteins arrive at their final locations, ready to work.

Rough then Smooth• The rough ER is where polypeptides are built.

• The smooth ER has several functions– Most importantly:

• Lipid synthesis (for membranes)• Home to many enzymes.

Golgi• Structure: folded membranes

• Function: Proteins are finished– folded into correct conformations & quarternary

structures– Modified chemically

• Addition of chemical groups (e.g. heme in hemoglobin, etc.)

• Modified amino acids

– label proteins so they get delivered to the right places.

• What might they be labeled with?

Nucleus(DNA)

mRNA

RoughEndoplasmicReticulum

Ribosome

AminoAcids

SmoothEndoplasmicReticulum

GolgiApparatus

TransportVesicle

OutgoingTransportVesicles

Lysosome

Mito-chondria