1. Chapter 6 The Cell: Endomembrane System–. Endoplasmic Reticulum,
Chapter 6 The Cell: Endomembrane System– Endoplasmic Reticulum, Golgi Apparatus, Lysosomes, Peroxisomes, Vacuoles, Vesicles

2. Overview
Play key role in synthesis (& hydrolysis) of macromolecules in cell
Various “players” modify macromolecules for various functions

3. Endoplasmic Reticulum
Function
manufactures membranes & performs many bio-synthesis functions
Structure
membrane connected to nuclear envelope & extends throughout cell
accounts for 50% membranes in eukaryotic cell
rough ER = bound ribosomes
smooth ER = no ribosomes

4. Types of ER

5. Smooth ER function Factory processing operations
many metabolic processes
synthesis & hydrolysis
enzymes of smooth ER…
synthesize lipids, oils, phospholipids, steroids & sex hormones
hydrolysis (breakdown) of glycogen (in liver) into glucose
detoxify drugs & poisons (in liver)
ex. alcohol & barbiturates

6. which cells have a lot of rough ER?
Rough ER function
Produce proteins for export out of cell
protein secreting cells
packaged into transport vesicles for export
which cells have a lot of rough ER?
Which cells have a lot of ER?
protein production cells like pancreas = production of digestive enzymes (rough endoplasmic reticulum from a cell of exocrine pancreas (88000X))

7. Membrane Factory 2005-2006 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

10. which cells have a lot of Golgi?
Golgi Apparatus
Function
finishes, sorts, & ships cell products
“shipping & receiving department”
center of manufacturing, warehousing, sorting & shipping
extensive in cells specialized for secretion
Cells specialized for secretion?
endocrine glands: produce hormones
pituitary, pancreas, adrenal, testes, ovaries
exocrine glands: produce digestive enzymes& other products
pancreas, mammary glands, sweat glands
which cells have a lot of Golgi?

11. Golgi Apparatus Structure flattened membranous sacs = cisternae
look like stack 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” (transport)
cis
trans

12. Golgi Apparatus

13. 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 barcodes

14. Putting it together…

17. Lysosomes
Structure
membrane-bounded sac of hydrolytic enzymes that digests macromolecules
enzymes & membrane of lysosomes are synthesized by rough ER & transferred to the Golgi
only in
animal cells

18. Lysosomes 1960 | 1974 Function a little “stomach” for the cell
lyso– = breaking things apart
–some = body
also the “clean up crew” of the cell
Lysosomes were discovered quite recently, in 1960s, by Christian de Duve. This discovery was so important that he was awarded the 1974 Nobel prize.
Why was this discovery so important?
1974 Nobel prize: Christian de Duve
Lysosomes discovery in 1960s

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

20. Where old proteins go to die! “Let’s go to the video tape!”
The Recycler
“Let’s go to the video tape!”
(play movie here)
Fuse with organelles or macromolecules in cytosol to recycle materials

21. Lysosomal enzymes Lysosomal enzymes work best at pH 5
organelle creates custom pH
how?
proteins in lysosomal membrane pump H+ ions from the cytosol into lysosome
why?
enzymes are very sensitive to pH
enzymes are proteins — pH affects structure
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!
lysosomes create a space where cell can digest macromolecules safely
rupturing a few lysosomes has little impact on a cell (pH of cytosol affects functionality of the lysosomal enzymes), but massive leakage from lysosomes can destroy cell
why evolve digestive enzymes which function at pH so different from cytosol?
digestive enzymes won’t function well if leak into cytosol = most times don’t want to digest yourself!
low pH = acid environment cause oxidation (removing electrons) & promotes hydrolysis

22. When things go wrong…
Tay-Sachs
What if a lysomome digestive enzyme doesn’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

23. Sometimes its supposed to work that way…
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
Feedback mechanism
There are sensors in the cell that monitor growth. They trigger self-destruct when they sense processes gone awry.
Brown spots on leaves too.
Virus infected plant cell auto-destructs and even kills cells around it to wall off virus.

24. syndactyly
Fetal development
15 weeks
6 weeks

26. Peroxisomes Other digestive enzyme sacs in both animals & plants
breakdown fatty acids to sugars
easier to transport & use as energy source
detoxify cell
detoxifies alcohol & other poisons
produce peroxide (H2O2)
must breakdown H2O2  H2O

27. “Let’s go to the video tape!”
Vacuoles & vesicles
Function
little “transfer ships”
Food vacuoles
phagocytosis, fuse with lysosomes
Contractile vacuoles
in freshwater protists, pump excess H2O out of cell
Central vacuoles
in many mature plant cells
“Let’s go to the video tape!”
(play movie here)

28. Vacuoles in plants Functions storage
stockpiling proteins or inorganic ions
depositing metabolic byproducts
storing pigments
storing defensive compounds against herbivores
selective membrane
control what comes in or goes out

29. Vacuole

30. Vesicles
Vesicles

31. Putting it all together…
“Let’s go to the video tape!”
(play movie here)
Putting it all together…

32. Any Questions??