Question

Describe the key features of each structure including function, organization, cellular location, and some of the most important molecules that characterize the structure.

a. Ribosome

b. Nucleolus

c. Nuclear Pore Complex

d. Endoplasmic Reticulum

What type of microscopy could you use to “see” the structure? Would your method allow a direct or indirect visualization? Explain your choice based on structure size and the resolution needed to detect the structure.

These are the tools that we covered: transmission electron microscopy (TEM), electron microscopy, fluorescence microscopy, immunofluorescence microscopy. Feel free to mention other tools that you might know of.  

Describe the steps of ribosome biogenesis. What is imported from the cytoplasm to the nucleus and what is exported from the nucleus to the cytoplasm. Use the following diagram to help you.

 Figure 6-45 The function of the nucleolus in ribosome and other ribonucleoprotein synthesis. The 45S precursor rRNA is packaged in a large ribonucleoprotein particle containing many ribosomal proteins imported from the cytoplasm. While this particle remains at the nucleolus, selected components are added and others discarded as it is processed into immature large and small ribosomal subunits. The two ribosomal subunits attain their final functional fom only after each is individually transported through the nuclear pores into the cytoplasm. Other ribonucleoprotein complexes, including telomerase shown here, are also assembled in the nucleolus.

Answer 1

1.Ribosome

• Protein synthesis
• Made up of two sub-units of RNA
• found in cytoplasm and on ER
• observed through electron microscopy

2.Nucleolus

• active site of rRNA synthesis
• made up of DNA+RNA+PROTEINS
• found in nucleoplasm of nucleus
• observed through electron microscopy

3.Nuclear pore complex

• large protein complex
• provide channel for exhange of RNA and protein b/w cytoplasm and nucleoplasm
• found in nuclear membrane
• observed through electron microscopy

4.ER

made up of network of folded membrane which consist of a phospholipid bilayer with proteins.

• RER-protein synthesis and SER-lipid and steroid synthesis
• Found in cytoplasm associated with nuclear membrane
• observed through Light microscope

#Steps of ribosome biogenesis

• Modification
• Cleavage
• exonuclease digestion
• Assembly

Ribosome biogenesis in prokaryotes takes place in cytoplasm and in eukaryotes it takes place in cytoplasm and nucleolus.

#Ribosomal proteins and telomerase proteins are imported to nucleus from cytoplasm while subunits of ribosome (40S and 60S) are exported from nucleus to cytoplasm.