ER and Golgi apparatus Flashcards
What is the endoplasmic reticulum (ER)?
Endoplasmic reticulum is a network of membranes organized into flattened sacs and tubules that are present within eukaryotic cells.
The endoplasmic reticulum (ER) is a large, dynamic structure that serves many roles in the cell including: (6)
- Protein synthesis
- Calcium storage
- Lipid metabolism
- maintenance of cellular homeostasis
- Transports materials in the cell
- Detoxification
The diverse functions of the ER are performed by distinct domains consisting of
- tubules
- sheets
- nuclear envelopes
What does the rER function in?
protein synthesis, folding, modification, and transporting the proteins outside the cell to their proper destinations
State three functions of the smooth endoplasmic reticulum.
- Synthesis of phospholipids and cholesterol
- Provides the enzymes that control glycogen breakdown when glycogen is to be used for energy.
- Provides enzymes that are capable of detoxifying substances.
Give an overview of the secretion process for proteins synthesized by the ER.
- The rER synthesize proteins to be secreted to the exterior or to be incorporated into cell membrane or other cell components.
- The sER packages the secretory product into transport vesicles, which bud off and move to the Golgi complex.
- The transport vesicles fuse with the Golgi complex, open up, and empty their contents into the closest Golgi sac.
- The newly synthesized proteins from the ER travel by vesicular transport through the layers of the Golgi complex which modifies the raw proteins into final form and sorts and directs the finished products to their final destination by varying their wrappers.
- Secretory vesicles containing the finished protein products bud off the Golgi complex and remain in the cytosol, storing the products until signalled to empty.
- On appropriate stimulation, the secretory vesicle fuse with cell membrane, open, and empty their contents to the cell’s exterior by exocytosis.
- Lysosomes also bud from the Golgi complex.
- [Diagram 1] [Diagram 2] [Diagram 3]
True or False
Themedialandtranscompartments of the Golgi stack correspond to the cisternae in the middle of the Golgi complex and are the sites of most protein modifications.
True
True or False
Protein synthesis requires localization of ribosomes to the cytosolic face of the ER (thus rER), and the defined pathway that regulates protein synthesis does not involves co-translational docking of the mRNA/ribosome complex on the ER membrane.
False.
The defined pathway does involves co-translational docking of the mRNA/ribosome complex on the ER membrane. Check out functions of the membrane proteins in the previous deck.
Translation of secretory or integral membrane proteins initiates in the cytosol, then ribosomes containing these mRNAs are recruited to the ER membrane via a signal sequence within the amino terminus of the nascent polypeptide that is recognized and bound by the ____________________________.
signal recognition particle
Thee functtiionn of signalal recoggnintitiionn parrttiiclle (SRPP)) is ____________________________.
a.. to enhannccee G-protein-couupplele recepttoorr signaalilingg
b.. to recognnizizee the amininoo aciid sequennccee forr N-linkedd glycossyylalatitionn
c. to distinguiishh phosspphhoroyrlyalatetedd proteiinss from dephoossphpohroyrlyalatetedd proteiinss
d.. to assoocciaiatete witith signaalilingg hormoonneess
e.. to recognnizizee a signalal pepttiidee andd delliverr riibboosomeess to endoppllasmmicic retiiccuululum
Choice E.
State two key differences between peroxisomes and lysosomes.
Peroxisomes form by self replication/budding off from smooth ER, whereas lysosomes are formed by breaking off from the Golgi apparatus.
The enzymes contained in peroxisomes are oxidases whereas those contained in lysosomes are hydrolases.
In RER, ribosomes are located on the ______________ side. (cytoplasmic or luminal?)
cytoplasmic
As the protein is synthesized, it is transported into the luminal side for processing and folding.
