Protein synthesis (Click to select text)

Biology Transcription- In the process of transcription a DNA molecule uncoils at a point along its structure where the neccessary information to construct the needed protein is. The weak hydrogen bonds between the DNA bases then break, using the neccessary enzymes, which opens the molecule out, then free RNA nucleiotides in the nucleus combine with their complementary bases on one side of the DNA it is not important which side it joins with as they both contain the same information. As RNA has no thymine the DNA's adenine combines with the RNA's uracil instead the other bases remain the same. Weak hydrogen bonds form between the DNA and RNA bases and the RNA develops a strong sugar backbone. The DNA molecule then recoils.ATP is needed for transcription to occur. Translation- Translation of RNA occurs when the transcribed RNA from the nucleus , which is now called messanger RNA [mRNA] as it contains the protein information. This mRNA leaves the nucleus through a nuclear pore, DNA is too large a molecule to do this, to the cytoplasm. In the cytoplasm there are free transfer RNA [tRNA] molecules which hve three protruding bases these sets of three on the tRNA are called anti-codons. Each tRNA molecule attracts different amino acids, of which there are around twenty, and they "stick" to the tRNA and depending on which tRNA molecule it is it wil attract a diferent amino-acid.On the RNA every three bases are called codons these are complementary to the anti-codons of the tRNA. For instance a codon of - GAA - would pair with the anti-codon- CUU -. In this fashion weak hydrogen bonds form between the tRNA and RNA molecules. This occurs at the ribosome. The ribosome is a organelle in the cytoplasm or on the rough endoplasmic reticulum it moves the unit of RNA and tRNA along itself so that strong peptide bonds can form between the amino acids which form polypeptide chains which then form proteins. The RNA and tRNA are normally used several time before breakdown.