#INTRODUCTION:
2)They are also called protein factories of the cell, as they are responsible for protein synthesis.
3) First observed by George Palade in 1955 using an electron microscope.
(Also called Palade particles.)
#LOCATION:
->They are found freely floating in the cytoplasm.
#CHEMICAL COMPOSITION OF RIBOSOMES:
->They are made up of roughly 60% rRNA and 40% proteins.
#STRUCTURE:
->It has two subunits - a large subunit and a small subunit, which fit together during translation.
#SMALL SUBUNIT OF RIBOSOME (30S &40S)
->They contain one molecule of rRNA, or ribosomal RNA (16S in prokaryotes and 18S in eukaryotes).
->They bind to mRNA and read the genetic code.
#LARGE SUBUNIT OF RIBOSOME (50S &60S)
->They contain rRNA molecules (23S & 5S in prokaryotes and 28S , 5.8S & 5S in eukaryotes).
->It has enzymatic ( peptide transferase ) activity that forms peptide bonds between amino acids.
#BINDING SITES ON RIBOSOMES DURING TRANSLATION:
1) A SITE aminoacyl site ) - entry of new t-RNA carrying an amino acid.
2) P SITE(Peptidyl site) - holds the t-RNA with the growing polypeptide chain.
3)E SITE(Exit site)- site where empty t-RNA exits after delivering its amino acid.
#FUNCTIONS OF RIBOSOMES:
1)PROTEIN SYNTHESIS - main function is to translate mRNA into a polypeptide chain. The ribosome reads mRNA codons and links amino acids accordingly.
2)POLYSOME FORMATION- Several ribosomes attach to a single mRNA strand, forming a polyribosome. Also called a polysome, which allows rapid synthesis of multiple copies of proteins.
3)In freely floating ribosome plasma use enzymes and cytoskeleton protein for protein synthesis.
4)ENZYME FORMATION-ribosomes help in synthesising various enzymes necessary for metabolism.
5)REPAIR AND REPLACEMENT - Ribosomal proteins are involved in cellular damage by synthesising replacement proteins.
6) Bound ribosomes on the rough endoplasmic reticulum secrete proteins, membrane proteins and lysosomal enzymes for protein synthesis.
Thus, ribosomes play a vital role in the cell by serving as the site of protein synthesis, ensuring the proper growth, repair, and functioning of all living organisms.
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