From CellBiology


Chloroplast Ribosome

Cytoplasmic structure formed from RNA and proteins that assembles to synthesise proteins. Ribosomes may be either free in the cytoplasm or attached to the endoplasmic reticulum, forming rough endoplasmic reticulum.

Ribosome Structure

  • All RNA components mRNA, rRNA and tRNA come together in this structure
  • two ribosome types with identical structure
  • different locations
  • free and membrane bound
    • Free in cytoplasm
    • Bound to endoplasmic reticulum

Ribosome Function

  • Protein Synthesis
  • complexes where RNA sequences are converted to amino acid (aa) sequences
  • Codons 3 NTPs = 1 AA
    • AA incorporated at 20/sec
    • average sized protein takes 20-60 seconds to assemble
  • Synthesis from amino- to carboxy- terminal of protein
  • many ribosomes can bind 1 mRNA


  • polyribosomes or polysomes are the EM visible granules
  • many ribosomes bound to a single mRNA
  • single ribosome covers a 54bp mRNA region
  • the synthesised single amino acid chain can then be "modified"
    • in the cytoplasm or in specialised organelles
  • Protein Modification/Function



Essential Cell Biology

  • Chapter 14 Intracellular Compartments and Transport

Molecular Biology of the Cell

Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter New York and London: Garland Science; c2002

Molecular Cell Biology

Lodish, Harvey; Berk, Arnold; Zipursky, S. Lawrence; Matsudaira, Paul; Baltimore, David; Darnell, James E. New York: W. H. Freeman & Co.; c1999

The Cell- A Molecular Approach

Cooper, Geoffrey M. Sunderland (MA): Sinauer Associates, Inc.; c2000

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  • The ribosome returned Peter B Moore J Biol. 2009; 8(1): 8. Published online 2009 January 26. doi: 10.1186/jbiol103. PMID: 19222865
  • Insights into protein biosynthesis from structures of bacterial ribosomes. Berk V, Cate JH. Curr Opin Struct Biol. 2007 Jun;17(3):302-9. Review. PMID: 17574829
  • Ribosome structure. The ribosome in action. Dahlberg AE. Science. 2001 May 4;292(5518):868-9. PMID: 11341282
  • A structural understanding of the dynamic ribosome machine. Steitz TA. Nat Rev Mol Cell Biol. 2008 Mar;9(3):242-53. Review. PMID: 18292779



internal ribosomal entry site (IRES)


Wikipedia Ribosome