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?

On the exterior of the cell.

Explanation:

The black spots as mentioned in the given case would appear on the exterior of the cell after three hours, which suggests that the proteins or the enzymes had been discharged from the pancreatic cell. The mentioned method of labeling and then chasing the component is known as a pulse-chase experiment.  

In this experiment, the labeled compounds are used to follow the dynamics of cellular pathways and procedures. The molecules in a cell get produced and degraded spontaneously at various rates. These changes in the localization of the molecule and its expression levels with time can be determined by exposing or pulsing cells to a labeled compound.  

After this the cells are exposed sequentially to the same compound unlabeled, the process is termed as the chase. The compounds are generally labeled with fluorescent dyes or radioisotopes.  

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