Protein Synthesis
Identifying sites of protein synthesis in Chlamydomonas using erythromycin and cyclohexamide as protein synthesis inhibitors.
October 16, 2009
Introduction: In living cells, prokaryotic or eukaryotic, the synthesis (construction) of proteins is accomplished by similar machinery. Amino acids, ribosomes, messenger RNA (mRNA), and transfer RNA (tRNA), are all necessary for the building of functional proteins in a cell. Ribosomes are the site of protein synthesis in a cell, and there are two different types, depending on the type of cell. Only the 70S ribosomes are found in prokaryotes (bacteria, archaea). Eukaryotes, (cells that contain a membrane-bound nucleus), have both 70S and 80S ribosomes. The 70S ribosomes are present in mitochondria and chloroplasts of eukaryotic cells (Willey, et al, 20083). The theory of endosymbiosis is based on the thought that mitochondria and chloroplasts were, at one time, prokaryotic organisms that were engulfed into a eukaryotic cell and formed an equally beneficial relationship. Since mitochondria and chloroplasts contain their own DNA and self-replicate, their genetic codes are passed along with the rest of the cell when reproduction occurs. The two types of ribosomes made in a eukaryotic cell will respond differently when given certain antibiotics (Nelson, et al 2009). This experiment focused on two: erythromycin and cyclohexamide.
When given erythromycin, tRNA is inhibited from transferring from one site of ribosomal RNA (rRNA) to another site during protein synthesis. However, this inhibition only occurs in the 70S ribosome (DrugBank, 2011). In contrast, when a cell is given cyclohexamide, the 80S ribosomes are blocked from completing the process of elongation (the addition of triplet codons that are complimentary to an mRNA molecule). This occurs in the last step of elongation, during the translocation phase (Willey, et al, 20081). Translocation is the movement of the tRNA molecule from one part of
October 16, 2009
Introduction: In living cells, prokaryotic or eukaryotic, the synthesis (construction) of proteins is accomplished by similar machinery. Amino acids, ribosomes, messenger RNA (mRNA), and transfer RNA (tRNA), are all necessary for the building of functional proteins in a cell. Ribosomes are the site of protein synthesis in a cell, and there are two different types, depending on the type of cell. Only the 70S ribosomes are found in prokaryotes (bacteria, archaea). Eukaryotes, (cells that contain a membrane-bound nucleus), have both 70S and 80S ribosomes. The 70S ribosomes are present in mitochondria and chloroplasts of eukaryotic cells (Willey, et al, 20083). The theory of endosymbiosis is based on the thought that mitochondria and chloroplasts were, at one time, prokaryotic organisms that were engulfed into a eukaryotic cell and formed an equally beneficial relationship. Since mitochondria and chloroplasts contain their own DNA and self-replicate, their genetic codes are passed along with the rest of the cell when reproduction occurs. The two types of ribosomes made in a eukaryotic cell will respond differently when given certain antibiotics (Nelson, et al 2009). This experiment focused on two: erythromycin and cyclohexamide.
When given erythromycin, tRNA is inhibited from transferring from one site of ribosomal RNA (rRNA) to another site during protein synthesis. However, this inhibition only occurs in the 70S ribosome (DrugBank, 2011). In contrast, when a cell is given cyclohexamide, the 80S ribosomes are blocked from completing the process of elongation (the addition of triplet codons that are complimentary to an mRNA molecule). This occurs in the last step of elongation, during the translocation phase (Willey, et al, 20081). Translocation is the movement of the tRNA molecule from one part of
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