Kaplan Nursing Entrance Practice Exam

What do pores in the nuclear envelope allow to enter?

1. Small molecules only

2. Large molecules such as mRNA

3. Only DNA molecules

4. Proteins and enzymes only

The correct answer is: Large molecules such as mRNA

The correct answer is based on the role of nuclear pores in cellular biology. Nuclear pores are large protein complexes that span the nuclear envelope, the double membrane surrounding the nucleus of a cell. These pores function as gateways that regulate the passage of molecules between the nucleus and the cytoplasm. Large molecules, such as messenger RNA (mRNA), are synthesized in the nucleus during the process of transcription and need to be transported out to the cytoplasm for translation into proteins. The nuclear pores facilitate the selective import and export of various molecules. They are capable of allowing large molecules to pass through, but this process often requires specific signals or transport mechanisms. In contrast, while small molecules can freely diffuse through the nuclear pores, they do not fully encapsulate the primary function of these structures, which is more focused on the transport of larger macromolecules. Furthermore, the nuclear envelope is not specifically permeable only to DNA molecules, as DNA is generally confined within the nucleus and does not typically pass through the pores. Proteins and enzymes are also transported; however, they do not encompass the primary examples of what is actively and accurately transported from the nucleus to the cytoplasm, particularly underlining the important transition of mRNA. Therefore, the focus on large molecules like m