what are ribosomes plzzz explain plzzzzzzz in detail
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The sequence of DNA that encodes the sequence of the amino acids in a protein, is transcribed into a messenger RNA chain. Ribosomes bind to messenger RNAs and use its sequence for determining the correct sequence of amino acids to generate a given protein. Amino acids are selected and carried to the ribosome by transfer RNA (tRNA)molecules, which enter the ribosome and bind to the messenger RNA chain via an anti-codon stem loop. For each coding triplet in the messenger RNA, there is a transfer RNA that matches and carries the correct amino acid for incorporating into a growing polypeptide chain. Once the protein is produced, it can then fold to produce a functional three-dimensional structure.
A ribosome is made from complexes of RNAs and proteins and is therefore a ribonucleoprotein complex. Each ribosome is divided into two subunits:
a smaller subunit which binds to a larger subunit and the mRNA,(30S) and
a larger subunit which binds to the aminoacylated tRNAs and the smaller subunit(50S).
When a ribosome finishes reading an mRNA molecule, these two subunits split apart. Ribosomes are ribozymes, because the catalytic peptidyl transferase activity that links amino acids together is performed by the ribosomal RNA. Ribosomes are often associated with the intracellular membranes that make up the rough endoplasmic reticulum.
Ribosomes from bacteria, archaea and eukaryotes in the three-domain system resemble each other to a remarkable degree, evidence of a common origin. They differ in their size, sequence, structure, and the ratio of protein to RNA. The differences in structure allow some antibiotics to kill bacteria by inhibiting their ribosomes, while leaving human ribosomes unaffected. In all species, more than one ribosome may move along a single mRNA chain at one time (as a polysome), each "reading" its sequence and producing a corresponding protein molecule.
The mitochondrial ribosomes of eukaryotic cells functionally resemble many features of those in bacteria, reflecting the likely evolutionary origin of mitochondria.[5][6]
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