What Is the Function of the Nucleolus?
Nuclei (nucleolus) usually appear as single or multiple homogeneous spherules, which are the most prominent structures in the eukaryotic interphase nuclei. The size, shape, and number of nucleoli vary with the type of organism, cell type, and cell metabolism. Cells with strong protein synthesis, such as secretory cells and oocytes, have large nucleoli, which can account for 25% of the total nucleus volume. Cells without protein synthesis capabilities, such as muscle cells and dormant plant cells, have small nucleoli. [1]
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- Nuclei (nucleolus) usually appear as single or multiple homogeneous spherules, which are the most prominent structures in the eukaryotic interphase nuclei. The size, shape, and number of nucleoli vary with the type of organism, cell type, and cell metabolism. Cells with strong protein synthesis, such as secretory cells and oocytes, have large nucleoli, which can account for 25% of the total nucleus volume. Cells without protein synthesis capabilities, such as muscle cells and dormant plant cells, have small nucleoli. [1]
- Overview
- The shape, size, and number of nucleoli vary depending on the biological species, cell type, and physiological state, but the functions of the nucleoli are the same. The main function of the nucleoli is to carry out
- Ribosomes are factories that synthesize proteins in cells. In a vigorously growing bacterium, there are about 20,000 ribosomes, whose proteins account for 10% of total cellular proteins, and RNA accounts for 80% of total cellular RNA.
- Ribosome structure
- The ribosome contains 40% protein and 60% RNA. The protein combines with RNA in a certain order to form two ribosomal subunits. Among them, RNAs are backbone structures. Some proteins do not directly bind to RNA, but bind to others. On protein components. Proteins, rRNA, and other cofactors in the ribosome together provide all the enzyme activities required for the translation process. These enzyme activities are only available in the presence of the overall ribosome structure.
- Ribosomes from different sources have slightly different shapes, sizes, and chemical compositions. They are generally divided into two types, 70S and 80S, according to different sedimentation coefficients. 70S ribosomes are found in bacteria, mitochondria and chloroplasts, and 80s ribosomes are found in eukaryotes. In the cytoplasm of organisms.
- All ribosomes are composed of two large and small subunits. The large and small subunits of the ribosome are bound together only when using mRNA as a template to synthesize proteins. After the peptide chain synthesis is terminated, the large and small subunits dissociate and dissociate in the cytoplasm. In the matrix. The ribosome does not work alone, but consists of multiple or even dozens of molecules connected to a single mRNA molecule, called polyribosome. In this way, longer mRNA can bind more ribosomes and improve protein. The speed of the composition.
- Although the prokaryotic and eukaryotic ribosome proteins and rRNAs are very different, their structures are generally similar, especially the small subunits responsible for binding to mRNA. Both prokaryotic and eukaryotic rRNAs have methylation. This methylation is related to the enzyme recognition of post-transcriptional processing of RNA. In addition, prokaryotic 5SrRNA and eukaryotic 5.8SrRNA are highly conserved and are often used to study biological evolution.