Question

it is synthesized by free floating ribosomes in humas a) pancreatic lipase b) insulin c) salivary amylase d) DNA helicase

Answer 1

Answer:

Explanation:

The correct answer is DNA helicase, since it is the only one whose final destination is inside the cell.

All other proteins are secreted (lipase and amylase are digestive enzymes, and insulin is a hormone found in blood) and therefore need to enter the exocytic pathway. For that to happen, translation occurs in the rough endoplasmic reticulum (RER) membrane, from which they will be imported to the RER lumen. After travelling in vesicles (they will go through the Golgi complex at some point), the vesicles will fuse with the plasmatic membrane and the proteins will be released outside the cell.

On the contrary, DNA helicase will get translated in the cytoplasm by free floating ribosomes. A nuclear localization signal (NLS) will help it go back to the cell nucleus, where helicase performs its function during DNA replication.

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Answer 2

Answer:

The correct answer is option d ) DNA helicase

Explanation:  

The final destination of  DNA helicase is inside the cell in contrast to the other given option.

DNA helicase are translated in the cytoplasm by free floating ribosomes and then via secretory pathway from ER through Golgi, it trans locates into the nucleus with the help of NLS (Nuclear localizing signals) where it helps to unwind the dsDNA in the process of Replication.

Rest of the given proteins are destined to trans locates to a particular group of cell (like insulin is a hormone found in blood, salivary amylase destined in the salivary gland , pancreatic lipase are to be found  in the pancreas) ,for this reason the need to be exported outside the cell. So they enter into exocytic pathway where translation occurs in the RER membrane, from which are are imported to the lumen of RER. Then via vesicular transport from ER to Golgi they are carried in the vesicles and fused with plasma membrane . After that are released outside the cell.