Follow newly labeled cargo through a specified pathway
In the usual eukaryotic secretory pathway described in the source, proteins associated with the rough endoplasmic reticulum move in vesicles to the Golgi for further modification and sorting. Secretory vesicles can then carry cargo onward. This is not a claim that every protein in every cell follows that route; the diagnostic explicitly defines the pathway for the protein under discussion. Worked model: a tracer is introduced only after a transport connection is blocked. A newly labeled cargo cannot already be waiting downstream from a time before labeling began. Distinguish the old unlabeled pool from the newly labeled pool, and keep the block’s location separate from the site of synthesis. If synthesis continues upstream, new label may be seen there even when new downstream arrivals are prevented. This is a causal prediction from a stated model, not a real experimental protocol. Draw the three boxes and the arrow that is blocked. Then explain which proposed observation would require an unstated bypass or a reversal of the route. Avoid replacing the specified mechanism with a general claim that the whole cell instantly stops functioning. The case’s short interval and initial labeling conditions deliberately limit the inference; later degradation, alternative secretion or a different protein would need additional information.
In a simplified eukaryotic-cell model, a newly labeled secreted protein follows rough ER→Golgi→secretory vesicle. Labeling starts after transport from the ER to the Golgi has been completely blocked. Protein synthesis continues, and no labeled protein was present before the block. Over the short observation interval, which pattern is consistent with this model?
- The label is introduced only after the block, so there is no previously labeled Golgi pool. New synthesis can label the ER, but the stipulated block prevents that new cargo from reaching the Golgi. The inference concerns this model and interval, not every protein-trafficking route.
Compare the other answer choices
The question stipulates the ER-to-Golgi pathway for this cargo; the block does not establish a bypass.
This reverses the supplied route and ignores the complete ER-to-Golgi block.
The model says synthesis continues and places entry at rough ER, not protein synthesis in the Golgi.
Try it, then explain it.
Complete a short set without looking at the example. After each answer, explain which evidence or rule supports your decision and why the alternatives do not fit.
Sources & authorship
Original Slope explanations and examples. References support the concepts; they are not the source of copied questions. Independent educator review is pending.
Lumen/OpenStax legacy CC-BY edition—Endomembrane System and Proteins