1. The Endomembrane System
Regulates protein traffic and performs
metabolic functions in the cell
Includes many different structures:
Endoplasmic Reticulum (and vesicles)
Golgi Apparatus (and vesicles)
Lysosomes
Vacuoles

2. Endoplasmic Reticulum
Function
Manufactures membranes and performs many bio-synthesis functions
Structure
Membrane connected to nuclear envelope & extends throughout cell
Accounts for 50% of membranes in eukaryotic cells
Types
Rough ER= has ribosomes bound to it
Smooth ER=does not have ribosomes bound to it

3. Endoplasmic Reticulum

4. Smooth Endoplasmic Reticulum
Functions
Metabolic processes
Synthesis and hydrolysis
Enzymes of smooth ER
Synthesize lipids, oils, phospholipids, steroids & sex hormones
Hydrolysis of glycogen into glucose in liver
Detoxify drugs and poisons (in liver)
Pumps calcium ions for muscle function

5. Rough Endoplasmic Reticulum
Function
Produce proteins for export out of cell
Protein secreting cells
Packaged into transport vesicles for export

6. Membrane Factory Synthesize membrane phospholipids
Build new membrane
As ER membrane expands, bud off & transfer to other parts of cell that need membranes
Synthesize membrane proteins
Membrane bound proteins synthesized directly into membrane
Processing to make glycoproteins

7. Endoplasmic reticulum
Which types of cells have a lot of rough ER?
How might smooth ER play a role in “alcohol tolerance”?

8. Golgi Apparatus Function: Finishes, sorts & ships cell products
Shipping and receiving department
Extensive in cells specialized for secretion

9. Golgi Apparatus Structure Flattened membranous sac=cisternae
Look like stacks of pita bread
2 sides=2 functions
Cis=receives material by fusing with vesicles=“receiving”
Trans=buds off vesicles that travel to other sites=“shipping”

10. Golgi Processing
During path from cis to trans, products from ER are modified into final form
Tags, sorts, & packages materials into transport vesicles
Golgi=“UPS headquarters”
Transport vesicles=“UPS trucks”
Delivering packages that have been tagged with their own barcode

11. Protein-carrying vesicles from the endoplasmic reticulum
transfer substances to the cis region of the Golgi apparatus.
The Golgi chemically modifies proteins in its lumen…
…and “targets” them to the correct addresses.
Rough
endoplasmic
reticulum
Inside of cell
cis region
Golgi apparatus
trans region
Cisternae
Flow of material
Proteins for use
within the cell
Proteins for use
outside the cell
Plasma
membrane
Outside of cell
Play the video

12. Lysosomes Function: A little “stomach” for the cell
Lyso-=breaking things apart
-some=body
Clean up crew of the cell

13. Lysosome
Structure
Membrane bounded sac of hydrolytic enzymes and molecules that digests macromolecules
Enzymes & membrane of lysosomes are synthesized by rough ER & transferred to the golgi
Only in animal cells

14. Lysosomes in the Cell

15. Cellular digestion Lysosomes fuse with food vacuoles
Polymers are digested into monomers
Pass to cytosol to become nutrients of cell

16. Lysosomal enzymes Lysosomal enzymes work best at pH 5
Organelle creates custom pH
Enzymes are very pH sensitive
Why evolve digestive enzymes which function at pH different from cytosol
Digestive enzymes won’t function well if leak into cytosol=don’t want to digest yourself

17. Cell death… Apoptosis=cell death
Critical role in programmed destruction of cells in multicellular organisms
Auto-destruct mechanism
“cell suicide”
Some cells have to die in an organized fashion especially during development
Ex. Development of space between your fingers during embryonic development
ex. If cell grows improperly this self destruct mechanism is triggered to remove damaged cell
Cancer over rides this to enable tumor growth

18. When things go wrong…
What if a lysosome digestive enzyme didn’t function
Don’t digest a biomolecule
Instead biomolecule collects in lysosomes
Lysosomes fill up with undigested material
Lysosomes grow larger & larger
Eventually disrupt cell & organ function
Lysosomal storage diseases are usually fatal
Tay-Sachs disease
Lipids build up in brain cells
Child dies before age 5

19. Peroxisomes Other digestive enzyme sacs In both plants and animals
Breakdown fatty acids to sugars
Easier to transport & use as energy source
Detoxify cell
Detoxifies alcohol & other poisons
Produce perioxide (H2O2)

20. Central Vacuole Functions in plants Storage Maintains turgor pressure
Stockpiling proteins or inorganic ions
Depositing metabolic byproducts
Storing pigments
Storing defensive compounds against herbivores
Selective membrane (tonoplast)
Control what comes in and out
Maintains turgor pressure
Often largest structure in plant cell

21. Other Types of Vacuoles
Food vacuoles
Are formed by phagocytosis
Contractile vacuoles
Pump excess water out of protist cells

22. The Endomembrane System: A Review
The endomembrane system is a complex and dynamic player in the cell’s compartmental organization