Ribosomes are the cell's sites of protein synthesis. They are composed of ribosomal RNA and proteins and exist as large and small subunits. Ribosomes were first observed in the 1950s and can be either membrane-bound or free in the cytoplasm. They translate mRNA into proteins through the attachment of amino acids. Ribosomes require mRNA, tRNAs carrying amino acids, and the proper subunits coming together to produce proteins, which are then released into the cell. Antibiotics can inhibit bacterial ribosomes and disrupt protein synthesis. Disorders of ribosome biogenesis can also cause diseases.

1. Ribosome
YOGESH VISHWAKARMA
JAY PATEL

4. Introduction
•Cell’s factory; site for protein
synthesis (Translation)
•Also know as Translational Apparatus
•Non-membranous organelle
•Mostly attached to Rough ER
•Also found free
•Made up of rRNA and ribosomal
proteins

5. How did we know about it?
•First observed during mid 1950s by George
Emil Palade
•By electron microscope as dense particles
•First named Microsomal Particles
•Its detailed structure was discovered in
2000 and 2001

6. Types of Ribosome
•Classified according to their location
•Membrane-Bound Ribosomes
• Synthesize proteins for membranes and
exocytosis (Used outside the cell)
• Attached to ER and other organelles
•Free Ribosomes
• Found freely in cytoplasm (Red arrows)
• Synthesize proteins that function inside the
cytosol (Used inside the cell e.g. food
metabolism)

7. Structure and Composition
•Made up of rRNAs and distinct
Ribosomal Proteins
•3 (Prokaryotic) or 4 ( Eukaryotic) rRNAs
•And 40 to 80 different proteins
•Arranged into two pieces while
Translation
• Small ribosomal subunit (30s)
• Large ribosomal subunit (50s)

8. Large Subunit
•Contains the active site of ribosome
•The site where new peptide bonds are
formed (Green)
•Contains Aminoacyl binding site
•Contains Peptidyl binding site
•It uses peptidyl transferase to catalyze the
process(Green)
•Made of two rRNA strands (Yellow and
Orange)
•And many protein strands (Blue)

10. Small Subunit
•In charge of information flow
•Pairing codons with anti-codons
•Intake of mRNA
•mRNA enters through the opening in
the left side
•Made of rRNA (Orange)
•And protein strands (Blue)
•Contains the entry and exit sites of
mRNA

12. Ribosome Biogenesis
•It is the process of making Ribosomes in
the nucleus
•The protein parts are made in the
cytoplasm (Ribosome)
•Then transferred to the nucleus (Nuclear
Pores)
•rRNAs are transcribed in the nucleolus
•The ribosomal proteins and rRNAs bind
together
•Small and large subunits are made
•They are transported out of nucleus (Pores)

13. Function
•The one and only function is Protein
Synthesis
•This process is called Translation
•Begins with transcription of mRNA in
the nucleus
•mRNA travels to the cytoplasm with
specific codes
•It binds with the small subunit of the
ribosome
•The two subunits come together

14. Continued
•tRNAs transfer amino acids to the
ribosome
•Translation is started by AUG codon
•Starting amino acid is methionine
•Amino acids are attached in the
active site to form peptide chains
•Synthesis is stopped when a stop
codon comes (UAA, UGA UAG)
•The chain exits through the exit
tunnel into cytoplasm or ER

15. Functional Requirements
•A secure site for operation
• Formed by binding of two subunits
•A supply of information or blueprints
• Supplied by nucleus through mRNA
•A supply of amino acids to build from
• Transferred by tRNA, acquired from food
•Means of releasing it into cytoplasm
• Exits through the exit tunnel or cleft (Large
subunit)

16. Reaction to Anti-Biotics
•Several anti-biotics work by inhibiting
synthesis of prokaryotic ribosomes
•Some antibiotics such as Streptomycin
inhibit the small subunit
•While other antibiotics such as
Erythromycin inhibit the large subunit
•Antibiotics may not affect eukaryotic
cell ribosomes

17. Common Disorders
•Most of the disorders associated with
ribosome have abnormal biogenesis
•It is the abnormal formation of
ribosomes
•Mostly they get destroyed but they
escape in rare cases
•Some major diseases caused by
abnormal ribosome;
• Diamond-Blackfan anemia
• Treacher Collins syndrome
• Cartilage-hair hypoplasia

18. Keep your factory safe

19. Questions

20. References
•https://en.wikipedia.org/wiki/Ribosome#Discovery
•https://bscb.org/learning-resources/softcell-e-learning/ribosome/
•http://pdb101.rcsb.org/motm/10
•https://micro.magnet.fsu.edu/cells/ribosomes/ribosomes.html
•https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2858486/
•Cell Biology & Histology, Gartner L.P., Hiatt J.L., 7th Edition
•Essential Cell Biology, Alberts, Bray, Hopkins, Lewis, 4th Edition

21. Hope you learned something,
Thank You!