Lecture 11 Real
What is the signal hypothesis?
Blobel postulated (then demonstrated) that proteins secreted out of the cell contain an intrinsic signal that governs them to and across membranes and allows for their localization in the correct location of the cell.
Cells of the pancreas will incorporate radioactively labeled amino acids into proteins. This "tagging" of newly synthesized proteins enables a researcher to track the location of these proteins in a cell. In this case, we are tracking an enzyme that is eventually secreted by pancreatic cells. Which of the following is the most likely pathway for movement of this protein in the cell? ER → Golgi → nucleus ER → Golgi → vesicles that fuse with the plasma membrane Golgi → ER → lysosome nucleus → ER → Golgi ER → lysosomes → vesicles that fuse with the plasma membrane
ER → Golgi → vesicles that fuse with the plasma membrane
What is the endomembrane system composed of?
ER, Golgi complex, nuclear envelope (vesicles move between them)
What is the smooth ER?
It extends from the rough ER to form a network of membrane tubules. Unlike rough ER, smooth ER does not have ribosomes on the outer surfaces of its membrane. However smooth ER contains unique enzymes that make it functionally more diverse than rough ER. As mentioned above one of the functions of smooth ER is to detoxify drugs.
What is the rough ER?
It is continuous with the nuclear membrane and usually is folded into a series of flattened sacs. The outer surface of rough ER is studded with ribosomes, the sites of protein synthesis.
What does the smooth ER do?
Makes lipids and carbohydrates and detoxifies
What is the Golgi body?
Organelle that modifies, sorts, and packages proteins and other materials from the ER for storage in the cell or secretion out of the cell.
What does the rough ER do?
Protein synthesis and processing
What is the name of the protein that targets a newly synthesized polypeptide for entry into the ER lumen? an ER hook an exportin an importin a signal recognition particle
a signal recognition particle
Which of the following statements correctly characterizes bound ribosomes? the most common location for bound ribosomes is the cytoplasmic surface of the plasma membrane bound and free ribosomes are structurally different bound ribosomes generally synthesize membrane proteins and secretory proteins all of these answers are correct bound ribosomes are enclosed in their own membrane
bound ribosomes generally synthesize membrane proteins and secretory proteins
What allows for proper protein and lipid sorting within the Golgi bioluminescent nucleotides modified quaternary structures carbohydrate tags signal sequences
carbohydrate tags
Which structure is not technically part of the endomembrane system? nuclear envelope Golgi apparatus smooth ER rough ER chloroplast
chloroplast
What is the golgi apparatus?
flattened stacks that process, package, and deliver proteins and lipids from the ER
What is the endomembrane system?
network of organelles and structures that function in the transport of proteins/other macromolecules out/into cell EG golgi/ER
Vesicle transport occurs between the ER and the Golgi in both directions. Let's suppose a researcher added a drug to cells that inhibited vesicle transport from the Golgi to the ER but did NOT affect vesicle transport from the ER to the Golgi. If you observed cells microscopically after the drug was added, what would you expect to see happen over the course of 1 hour? (assume no significant new lipid synthesis can occur within 1 hour) both the ER and the Golgi would get smaller the ER would get smaller and the Golgi would get larger the ER would get larger and the Golgi would get smaller the ER and the Golgi would stay the same size both the ER and the Golgi would get larger
the ER would get smaller and the Golgi would get larger
Which model most accurately represents the current understanding of how proteins received from the ER progress through the Golgi apparatus? the nuclear flow hypothesis the vesicle transport hypotheiss the cisternal maturation hypothesis the cytoskeletal bridge hypothesis
the cisternal maturation hypothesis
Cells that line your intestines are specialized for nutrient absorption and are known to possess a numerous membrane proteins that transport small molecules and ions across the plasma membrane. Which of the following cell structures would you expect to be required for this function of the cells? the endoplasmic reticulum lysosomes peroxisomes cell walls
the endoplasmic reticulum
How are the signal sequences that direct molecules to particular destinations in the cell "read"? they bind to receptor proteins they bind to motor proteins are glycosylated by enzymes in the Golgi apparatus they enter transport vesicles
they bind to receptor proteins
Which of the following is not true of secreted proteins? they contain a signal that directs them into the lysosome they are transported between organelles in membrane-bound vesicles they are synthesized using ribosomes they enter the ER lumen during synthesis
they contain a signal that directs them into the lysosome
