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4.1 outline, simply, the steps in the synthesis of protein in the cell, including: the difference between DNA and RNA the production of messenger RNA the role of transfer RNA the formation of the polypeptide chain(s) the formation of the protein from polypeptide chains
outline, simply, the steps in the synthesis of protein in the cell, including:
- the difference between DNA and RNA
- the production of messenger RNA
- the role of transfer RNA
- the formation of the polypeptide chain(s)
- the formation of the protein from polypeptide chains
- The differences between DNA and RNA can be summarised in a table.
DNA |
RNA |
doubled stranded molecule of nucleotides in the shape of a spiral helix |
single stranded molecule of nucleotides |
contains a deoxyribose sugar |
contains a ribose sugar |
contains the nitrogen base thymine |
contains the nitrogen base uracil |
one type |
two types, messenger and transfer |
For a diagram of the structure of DNA, click here
Molecular Station
For the structure of RNA click here
Molecular Biology Notebook Online
- The first process in the synthesis of protein from DNA is transcription. The DNA molecule in the nucleus partly unzips and the code of nitrogen bases on the DNA is transferred to messenger RNA (mRNA). This is done by adenine bonding to uracil and guanine bonding to cytosine. Any non-coding sequences are removed at this point and the mRNA travels through the nuclear membrane to the cytoplasm.
- The second process is translation. Transfer RNA (tRNA) picks up amino acids in the cytoplasm and brings them to the mRNA that is attached to a ribosome. The first and second amino acids brought to the ribosome attach together, forming a peptide bond. The amino acids that link together will be determined by the order of bases on the mRNA. This linking continues down the code on the mRNA until a stop code is reached and then the chain of amino acids is released by the ribosome. This chain of amino acids is a polypeptide chain.
- The last process is the forming of a protein and this happens by the long polypeptide chain folding in particular shapes. The way they fold largely depends on the order of the amino acids. They fold several times to give their final structure.