Ribosomes structure and function essay

Table 12. Some inclusions in bacterial cells. Cytoplasmic inclusions Where found Composition Function glycogen many bacteria . E. coli polyglucose reserve carbon and energy source polybetahydroxybutyric acid (PHB) many bacteria . Pseudomonas polymerized hydroxy butyrate reserve carbon and energy source polyphosphate (volutin granules) many bacteria . Corynebacterium linear or cyclical polymers of PO4 reserve phosphate; possibly a reserve of high energy phosphate sulfur globules phototrophic purple and green sulfur bacteria and lithotrophic colorless sulfur bacteria elemental sulfur reserve of electrons (reducing source) in phototrophs; reserve energy source in lithotrophs gas vesicles aquatic bacteria especially cyanobacteria protein hulls or shells inflated with gases buoyancy (floatation) in the vertical water column parasporal crystals endospore-forming bacilli (genus Bacillus ) protein unknown but toxic to certain insects magnetosomes certain aquatic bacteria magnetite (iron oxide) Fe3O4  orienting and migrating along geo- magnetic field lines carboxysomes many autotrophic bacteria enzymes for autotrophic CO2 fixation site of CO2 fixation phycobilisomes cyanobacteria phycobiliproteins light-harvesting pigments chlorosomes Green bacteria lipid and protein and bacteriochlorophyll light-harvesting pigments and antennae

Ribosomes are the workplaces of protein biosynthesis , the process of translating mRNA into protein . The mRNA comprises a series of codons that dictate to the ribosome the sequence of the amino acids needed to make the protein. Using the mRNA as a template, the ribosome traverses each codon (3 nucleotides) of the mRNA, pairing it with the appropriate amino acid provided by an aminoacyl-tRNA . Aminoacyl-tRNA contains a complementary anticodon on one end and the appropriate amino acid on the other. For fast and accurate recognition of the appropriate tRNA, the ribosome utilizes large conformational changes ( conformational proofreading ) . [35] The small ribosomal subunit, typically bound to an aminoacyl-tRNA containing the amino acid methionine , binds to an AUG codon on the mRNA and recruits the large ribosomal subunit. The ribosome contains three RNA binding sites, designated A, P and E. The A site binds an aminoacyl-tRNA; the P site binds a peptidyl-tRNA (a tRNA bound to the peptide being synthesized); and the E site binds a free tRNA before it exits the ribosome. Protein synthesis begins at a start codon AUG near the 5' end of the mRNA. mRNA binds to the P site of the ribosome first. The ribosome is able to identify the start codon by use of the Shine-Dalgarno sequence of the mRNA in prokaryotes and Kozak box in eukaryotes.

Ribosomes structure and function essay

ribosomes structure and function essay


ribosomes structure and function essayribosomes structure and function essayribosomes structure and function essayribosomes structure and function essay