Tuesday, December 24, 2013
A Pulse Chase Experiment
Pancreatic cells, which secrete a large amount of digestive enzymes, are labeled with radioactive leucine and then chased for several hours with nonradioactive leucine. Photographic emulsions are prepared at different times during the chase. Where would the black spots appear on an emulsion prepared 3 hours after the pulse?
Exterior of the cell
Black spots would appear on the exterior of the cell after 3 hours, indicating that the proteins had been secreted from the cell.
What path does a protein in the secretory pathway take, starting from its site of synthesis?
Rough ER, secretory vesicles, Golgi apparatus, plasma membrane
Plasma membrane, secretory vesicles, Golgi apparatus, rough ER
Golgi apparatus, rough ER, secretory vesicles, plasma membrane
Rough ER, Golgi apparatus, secretory vesicles, plasma membrane
Proteins are synthesized in the rough ER, modified in the Golgi apparatus, and carried in secretory vesicles to the plasma membrane, where they are secreted.
During a pulse-chase experiment, photographic emulsions were prepared at different times during the chase, and radioactive spots were detected at the following times and locations: 5 minutes: rough ER; 10 minutes: Golgi apparatus; 40 minutes: endosomes; 70 minutes: lysosomes; 140 minutes: lysosomes. Which of the following conclusions can be drawn from these results?
The proteins were secreted.
The proteins traveled from lysosomes to endosomes.
The proteins did not travel through the Golgi apparatus.
The final destination of the proteins was the lysosome.
This conclusion can be drawn from the results, since the radioactive spots were last detected at the lysosome, which is not a secretory vesicle.
What scientific hypotheses can be tested by a pulse-chase experiment?
Solubility of a molecule
The steady-state amount of protein in a cell
Molecular zip code of a protein
Movement of molecules through a cell over time
Pulse–chase experiments allow for the tracking of molecules in a cell over time.
True or false? Proteins produced during the "chase" phase of a pulse–chase experiment are labeled with radioactive material.
During the chase phase, cells are provided with a large amount of
material, so they are
What is the first step in a pulse-chase experiment?
Preparing cells for electron microscopy
Incubating cells with a labeled molecule
Incubating cells with an unlabeled molecule
Examining cells for the location of the labeled molecules
Cells are first "pulsed" with a large amount of labeled material for a short time.
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MasteringBio 180 OCC
October 6, 2016 at 1:54 PM
Amazing! Thank you so much for this.
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