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Multiple Choice
Which of the following organelles do not contain proteins with a nuclear localization signal?
A
Chloroplasts
B
Mitochondria
C
Golgi Apparatus
D
Endoplasmic Reticulum
Verified step by step guidance
1
Understand the function of a nuclear localization signal (NLS): It is a sequence that 'tags' a protein for import into the cell nucleus by nuclear transport.
Recognize that organelles like chloroplasts and mitochondria have their own DNA and protein synthesis machinery, and they import proteins from the cytoplasm, some of which may have NLS for nuclear import.
Consider the Golgi Apparatus: It is involved in modifying, sorting, and packaging proteins for secretion or delivery to other organelles, but it does not require proteins with NLS as it does not interact directly with the nucleus.
Examine the Endoplasmic Reticulum (ER): It is involved in protein and lipid synthesis. Proteins synthesized in the ER are typically destined for secretion or for use in the cell membrane, not for the nucleus, so they generally do not have NLS.
Conclude that the Golgi Apparatus and the Endoplasmic Reticulum do not contain proteins with a nuclear localization signal, as their functions do not involve direct interaction with the nucleus.