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Ribosome facts for kids

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Peptide syn
Figure 1: Ribosomes assemble polymeric protein molecules whose sequence is controlled by the sequence of messenger RNA molecules. This is required by all living cells and associated viruses.

Ribosomes are important cell organelles. A ribosome is a large complex of RNA and protein. It does RNA translation, building proteins from amino acids using messenger RNA as a template. Ribosomes are found in all living cells, prokaryotes as well as eukaryotes.

A ribosome is a mixture of protein and RNA that starts its formation in the nucleolus of a cell. The nucleolus is found in the center of the nucleus. The nucleus is protected by the nuclear envelope, and lets things out through the nuclear pores.

The job of the ribosome is to make new proteins. It does this by moving along a strand of RNA and building a protein based on the code it reads. Making a protein this way is called translation. Ribosomes are usually found in the rough endoplasmic reticulum, but can also be found throughout the cytoplasm.

Ribosomer i arbete
Translation of mRNA (1) by a ribosome (2)(shown as small and large subunits) into a polypeptide chain (3). The ribosome begins at the start codon of mRNA (AUG) and ends at the stop codon (UAG).

Ribosome structure

Ribosome shape
Figure 2 : Large (red) and small (blue) subunit fit together

Ribosomes consist of two major subunits—the small ribosomal subunit reads the mRNA, while the large subunit joins amino acids to form a polypeptide chain. Each subunit is composed of one or more ribosomal RNA (rRNA) molecules and a variety of proteins.

Eukaryotes have 80S ribosomes, each consisting of a small (40S) and large (60S) subunit. Their small subunit has a 16S RNA sub-unit (consisting of 1540 nucleotides) bound to 21 proteins. The large subunit has a 5S RNA (120 nucleotides), a 28S RNA (4700 nucleotides), a 5.8S RNA (160 nucleotides) subunits and 46 proteins.

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