Week 1 Flashcards
Endoplasmic Reticulum
Divides the cytoplasm into two compartments - the luminal and cytoplasmic or cisternal/cytosolic.
Synthesizes, packages and processes various cell substances
Rough ER
Parallel sacks of flat, elongated cisternae, studded with ribosomes.
Make and modify proteins
Proteins are segregated for intracellular use
Export from the cell (collagen and cell membrane proteins)
Free Ribosomes
Sythesize proteins for intracellular use
Groups of ribosomes along single mRNA - poly(ribo)somes
Can be located in the mitochondria and chloroplasts
Polysomes
attached to RER synthesize proteins that are secreted or sequestered.
Function of Ribosomes
Site of mRNA translation
Permits synthesis of multiple copies of a protein
Ribosomes and protein synthesis
Ribosomes attach the the ER under the guidance of teh amino acid squence of the polypeptide chain being synthesized
Signal Hypothesis
The mechanism that describes how secretory proteins are directed to the ER
How do proteins exit the RER?
In vesicles transported to the cis portion of the Golgi apparatus
How is the Smooth ER different from the RER?
It lacks ribosomes and has tubular cisternae
What are some functions of the smooth ER?
Glycogen metabolism Lipid synthesis Phospholipid synthesis (other membranes) Detoxification Steroidogenesis Calcium REgulation
How would you describe the Golgi apparatus complex?
A cluster of flattened stacks of sacs called cisternae. Each Golgi stack has two faces, an entry and an exit (aka Cis and trans); with the cis being next to the ER and teh trans pointing towards the plasma membrane or the nucleus.
What does a Golgi apparatus do?
It can modify carbohydrates attached to glycoproteins and proteoglycans.
It can synthesize polysaccharides and oligosaccharides.
It can sythesize sphingomyelin and glycosphingolipids.
It can sort secretory products (it can mark lysosomal enzymes with M6P.
It packages and stores secretory products into secretory granules or vesicles.
What happens after the Golgi apparatus processes something?
The processed ‘cargo’ buds off and is either sorted to the secretory or lysosomal pathway (anterograde traffic) or back to the ER (Retrograde traffic)
What is the pathway followed by something being exocytosed?
ER->Golgi->Vesicle->cell surface
What happens when something follows an endocytotic pathway?
Extracellular material is internalized and degraded, going from plasma membrane through endosomes to lysosomes.
What happens before a vesicle fuses with an acceptor membrane?
It sheds its coat, so the two membranes can interact directly and fuse.
What are the two types of coated vesicles, and what does each do?
Clathrin-coated vesicles - transport products from Golgi to lysosomes or products from the exterior of the cell to lysosomes (like cholesterol) AKA into and out of the cell
COP - coated vesicles (comes from COat Protein) transport products between stacks of the Golgi (COP1 coated vesicles) and from ER to the Golgi (COP2-coated vesicles) AKA within the Golgi or to the Golgi
What is a primary lysosome?
The store site of lysosomal hydrolases.
Have no digestive enzymes
Homogeneous
Inactive Enzymes
What are secondary Lysosomes?
engaged in a catalytic process
Digestive Enzymes
Heterogeneous
Active enzymes
What is a residual body/ tertiary enzyme?
a cytoplasmic vacuole containing the leftover products after fusion with the contents of a lysosome.
