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The ribosome (from ribo nucleic acid and the Greek soma , meaning "body") is a large and complex molecular machine, found within all living cells, that serves as the primary site of biological protein synthesis (translation). Ribosomes link amino acids together in the order specified by messenger RNA (mRNA) molecules. 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. The sequence of DNA encoding for a protein may be copied many times into messenger RNA (mRNA) chains of a similar sequence. Ribosomes can bind to an mRNA chain and use it as a template for determining the correct sequence of amino acids in a particular protein.
Allium cells in different phases of the cell cycle The cell is the basic structural and functional unit of all known living organisms . It is the smallest unit of life that is classified as a living thing (except virus , which consists only from DNA/RNA covered by protein and lipids ), and is often called the building block of life. [ 1 ] Organisms can be classified as unicellular (consisting of a single cell; including most bacteria ) or multicellular (including plants and animals ). Humans contain about 100 trillion (10 14 ) cells. [ 2 ] Most plant and animal cells are between 1 and 100 micrometres and therefore are visible only under the microscope. [ 3 ]
The Biology Project > Cell Biology > PEV > Prokaryotes Prokaryotes Characteristics of prokaryotic cells. Bacteria & antibiotics