#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 by using an electron microscope .
(Also called as palade particles.)
#LOCATION:
->They are found freely floating in the cytoplasm .
#CHEMICAL COMPOSITION OF RIBOSOMES:
->They are made up of roughly 60% of rRNA and 40% of proteins .
#STRUCTURE:
->It has two sub units - a large subunit and a small subunit which fit together during photosynthesis .
#SMALL SUBUNIT OF RIBOSOME (30S &40S)
->They contain one molecule of rRNA or ribosomal RNA (16S in prokaryotes and 18S in eukaryotes).
->They binds to mRNA and reads 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 amino acid .
2) P SITE(Peptide site) - holds the t-RNA with growing polypeptide chains.
3)E SITE(Exit site)- site where empty t-RNA exit 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 polyribosome . Also called polysome which allow 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 rough endoplasmic reticulum secrete proteins , membrane proteins and lysosomal enzyme 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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