29. Ribosomes

Question 1

Ribosomes? General?

Answer 1

Ribosomes: site of protein synthesis - Ribosomes link amino acids together in the order specified by messenger RNA molecules. Ribosomes consist of RNAs and proteins and is therefore a ribonucleoprotein. 20 × 30 nm in size

Question 2

The subunits of Ribosomes?

Answer 2

Ribosomes consist of two major components:

• Small ribosomal subunit = reads RNA
• Large subunit = joins AA = form a polypeptide chain
• The rRNA molecules of both subunits are synthesized within the nucleus.
• Their numerous proteins are synthesized in cytoplasm but then enter the nucleus and associate with rRNAs.
• The assembled large/small subunits leave the nucleus and enter the cytoplasm to participate in protein synthesis.
• The large and small ribosomal subunits come together by binding an mRNA strand

Question 3

Process of protein synthesis occurring in ribosomes?

Answer 3

• The sequence of DNA which encodes the sequence of the amino acids in a protein is copied into mRNA chain.
• Ribosomes then bind to RNA chains - use its sequence to determine the correct sequence of amino acids.
• Amino acids are then selected, collected and carried to the ribosome by tRNA molecules which bind to the mRNA chain
• During the binding the correct translation of the nucleic acid sequence to amino acid sequence occur
• Once the protein is produced - it can then fold to produce specific functional 3D structures.