Cellular compartments

1. Cellular compartments and their function2. Evolution of cellular compartments3. How to make a 3D model of cellular compartment4. Cell organelles in the fluorescent microscope

A typical animal cells are very busy

Make proteins

Break-down

glucose

Duplicate DNA

Break-down

proteins

Oxidatetoxic

molecules

Add sugar to proteinsMake

ATP

Make mRNA

Burn fat

Inside a cell, many different chemical processes are performed simultaneously

Protein synthesisProtein modificationProtein degradation

Lipid synthesisLipid glycosylation

Oxidation of moleculesATP synthesis by

oxidative phospholylationetc

How do cells prevent chemical anarchy?

Chemical processes are segregated inside the cell

Bacteria: Enzyme complexes Eukaryotes: Compartmentalization

CompartmentalizationSeparation of cellular spaces by cell membranes

a b

two compartments: (a) and (b)

ab c

three compartments: (a), (b) and (c)

a

One compartment: (a)

Cell membrane

ab c

Compartmentalization allows a cell to….

• separate processes that might interfere

• independently regulate the microenvironment (pH, salt…)

• control ‘dangerous molecules’

• concentrate enzymes involved in the same process

Write down

7membrane-enclosed compartments!

1. Nucleus

2. Endoplasmaticreticulum (ER)

3. Golgi apparatus

4. Endosome

5. Lysosome

6. Peroxisome

7. Mitochondrion

8. Cytosol

9. [Chloroplast (plant cell)]

Endoplasmaticreticulum (ER)nucleus

Membrane-enclosed compartments of a typical animal cell

endosome cytosol

lysosome

Golgi apparatus

Mitochondrionperoxisome

endosome cytosol

lysosome

Golgi apparatus

Mitochondrion

Endoplasmaticreticulum (ER)

peroxisome

nucleus

In which cellular compartment do these processes take place?

1. DNA synthesis2. RNA synthesis3. Protein synthesis4. Lipid synthesis5. Protein modification6. Glycolysis7. ATP-synthesis by

oxidative phosphorylation

8. Oxidation of toxic molecules

9. Degradation of worn-out cell organelles and macromolecules

1. DNA synthesis2. RNA synthesis3. Protein synthesis4. Lipid synthesis5. Protein modification6. Glycolysis7. ATP synthesis by oxidative

phosphorylation8. Oxidation of toxic molecules9. Degradation of worn-out cell

organelles and macromolecules

endosome cytosol

lysosome

Golgi apparatus

Mitochondrion

Endoplasmaticreticulum (ER)

peroxisome

Nucleus

In which cellular compartment do these processes take place?

1,2

3

3

4

6

78

9

5

5

Nucleus

• contains main genome

• DNA and RNA synthesis

• is surrounded by a double membrane (inner and outer membrane-> nuclear envelope)

• Nuclear envelope is penetrated by nuclear pores

• outer nuclear membrane is continuous with the membrane of the ER

ER (endoplasmatic reticulum)

• a dynamic system of connected sacs and tubes of membranes

• synthesis of new membrane (lipid synthesis)

• rough ER: ribosomes attached to cytosolic surface

• ribosomes of rough ER synthesize proteins that are delivered into ER lumen or into ER membrane

•Smooth ER: storage of Ca2+

Golgi apparatus

• stack of membrane sacs

• modification and packaging of proteins and lipids

• situated near the nucleus

• receives proteins and lipids from the ER at cis-face

• dispatches proteins and lipids to cellular destination at trans- face

Trans Golgi network (TGN)Lower pH then rest of Golgi

Endosomes

• series of vesicles and tubes

• sorting endocytosed material

Lysosomes

• small sac of digestive enzymes

• low pH (pH 5), ( acidic hydrolases)

• site of intracellular degradation of ‘old’organelles, macromolecules and endocytosedmaterial

Peroxisomes

• contains enzymes that perform oxidative reactions

• uses molecular oxygen (O2) to oxidize organic molecules

• makes and destroys highly reactive H2O2

Cytosol

• contains many metabolic pathways (eg. Gycolysis)

• synthesis of proteins

• contains cytoskeleton (actinfilaments, microtubuli, intermediate filament)

Mitochondrium

• the cells power plant: synthesis of ATP by oxidative phosphorylation

• surrounded by a double membrane

• has its own genome, makes some of its proteins (but not all)

The main function of the membrane-enclosed compartments of a eukaryotic cell

endosomecytosol

lysosome

Golgi apparatusMitochondrionEndoplasmaticreticulum (ER)

peroxisome

Nucleus

Cytosol :Metabolic pathways, protein synthesis

Nucleus : contains main genome, DNA and RNA synthesis

Golgi: modification, sorting, packaging of proteins and lipids destined for many cell organelles and plasma membrane

ER: lipid synthesis, synthesis of proteins destined for some cell organelles and plasma membrane, Ca2+ storage

Mitochondria: ATP synthesis by oxidative phosphorylation

Lysosomes: intracellular degradation

Endosomes: sorting of endocytosed material

Peroxisomes: oxidation of toxic molecules

What happens to the membrane –enclosed compartments during mitosis?

NucleusGolgi

EREndosomesLysosomes

Mitochondria ChloroplastsPeroxisomes

Fragmentation into small vesicles

Distribution into daughter cells

Disassembly of nuclear envelope

Fragmentation?

Cellular compartments

1. Cellular compartments and their function2. Evolution of cellular compartments3. How to make a 3D model of cellular compartment4. Cell organelles in the fluorescent microscope

How did membrane enclosed compartments evolve?

?

?

Where do mitochondria come from?

?

How nuclear membranes and ER might have evolved

How cell organelles might have evolved…

Cis-Golgi ,Trans- Golgi Secretory Vesicles Transport VesiclesMicrotubuli, MitochondriaER , RibosomesEndosomes

The making of a 3D model of cellular compartments

•Take a slice of a cell (insulin secreting cell from the pancreas)• Look at the slice at different angles in the Electron Microscope• Reconstruct a three dimensional digital image• Step through the image and outline the membranes• Use a computer program to build a 3D model of the outlines

Summary

1. Advantages of membrane-enclosed compartments: • Segregation of processes within the cell• Independent microenvironments• Control of toxic/ destructive molecules

2. Membrane-enclosed compartments of the cell:• Cytosol, nucleus, ER, Golgi, lysosomes, endosomes,

peroxisomes, mitochondria, chloroplasts3. The nuclear envelope and the ER might have evolved by

invaginations of the plasma membrane4. Mitochondria and chloroplasts may have been endosymbiotic

prokaryotes5. During mitosis, membrane-enclosed compartments are divided into

both daughter cells

Cellular structures can be visualized with fluorescent dyes

RedGreenblue

Indian muntjac deerskin cell

Mitochondria

HeLa cell (human cancer cell)

Mitochondriaplasma membranenucleus

gray fox lung cell

Golgi apparatus

NIH 3T3 cells (mouse embryonic fibroblast)

Golgimitochondrianucleus

Viable Madin-Darby canine kidney (MDCK) cells

Golgilysosomesnucleus

U2OS (human osteosarcoma cell line )

ER

Live bovine pulmonary artery endothelial cells

ER

live bovine pulmonary artery endothelial cells

MitochondriaER

Bovine pulmonary artery endothelial cell

Mitochondriaperoxisomesnucleus

BREAK

Reorganization of the Golgi complex during mitosis

http://multimedia.mcb.harvard.edu/media.html

The inner life of the cell- Animation