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the process in which individual amino acids, whether of exogenous or endogenous origin, are connected to each other in peptide linkage in a specific order dictated by the sequence of nucleotides in DNA; this governing sequence is conveyed to the synthesizing apparatus in the ribosomes by mRNA, formed by base-pairing on the DNA template.
The manufacturing of proteins from amino acids. Within cells this process is guided by the specific sequence of nucleotides in DNA.
protein synthesisThe construction of protein molecules from AMINO ACIDS. This occurs in the cell CYTOPLASM on the basis of the GENETIC CODE in the DNA. Sections of DNA that code for the particular protein are first transcribed to MESSENGER RNA and this passes out of the cell nucleus to the cytoplasm. There, one or more ribosomes attach themselves to one end of the mRNA molecule and move along it to effect transcription, using, in the process, the sequence of RNA bases to indicate which amino acids should be selected from the cell pool and in what order. In this way the correct amino acids are linked together to form polypeptides and these are then joined to form the particular protein.
protein synthesisa complex anabolic process occurring in all cells, by which genes control the precise structure of proteins manufactured in the cell. The following summary of events refers to a EUKARYOTE cell:
- (a) DNA molecules in the chromosomes of the nucleus carry specific messages about how proteins are to be constructed.
- (b) the DNA of each gene carries instructions about one protein chain (see ONE GENE/ONE ENZYME HYPOTHESIS).
- (c) the two polynucleotide chains of the DNA molecule separate and messenger RNA nucleotides become attached in complementary pairing, the process being called TRANSCRIPTION.
- (d) the mRNA molecule leaves the DNA which reforms a double helix.
- (e) mature mRNA (see RNA PROCESSING) leaves the nucleus via pores in the NUCLEAR MEMBRANE and enters the cytoplasm where it becomes attached to one or more RIBOSOMES (See also POLYRIBOSOMES) near the ENDOPLASMIC RETICULUM.
- (f) with the aid of transfer RNA, TRANSLATION of the message in the mRNA takes place, with the formation of a POLYPEPTIDE CHAIN which later becomes coiled (see PROTEIN, POST-TRANSLATIONAL MODIFICATIONS).