Modelling the process of polypeptide synthesis

• Polypeptide synthesis is the formation of amino acids/polypeptides to create proteins used in important development and regulations of the body.
• The proteins are made by the ribosomes in the cell. This means both free ribosomes, and ribosomes on the endoplasmic reticulum (making it rough endoplasmic reticulum).
• Peptides are short chains of 5-20 amino acids.
• polypeptides are linear molecules, made of multiple peptides.
• proteins are functional unit, made up of one or more polypeptide. Proteins make up all living materials!
• Proteins can be either enzymes, which act as a catalyst for biochemical reactions in our body, which send chemical signals to regulate and/or adapt bodily functions.or hormonal
• DNA

  •  Deoxyribonucleic Acid
  • Base Pairs:Adenine, Guanine, Cytosine, Thymine  G=C &  A=T
  • Double stranded sugar phosphate 
• RNA

  • Ribonucleic Acid
  • Base Pairs:Adenine, Guanine, Cytosine, Uracil G=C &  A=U
  • Single stranded sugar phosphate
• Amino acids are simple organic compounds that contain a carboxyl (-COOH) and an amino (-NH2) grouP and are the building blocks of proteins.
• They can either be essential, Must be obtained food or non essential, Produced by our bodies.
• mRNA or messenger RNA is a  single stranded nucleic acid, consisting of a ribose sugar, phosphate backbone, and nitrogen bases (A, U, G and C)
• tRNA or transfer RNA is a small RNA molecule that transfers specific amino acids to the ribosome during formation of polypeptides.
• A codon is Set of three nitrogen bases in mRNA.
• An anticodon is a Complementary set of three nitrogen bases on tRNA.
• Transcription is the first main step in polypeptide synthesis which is carried out in the nucleus. A segment of a genes DNA sequence is copied and transferred from a double helical strand to a single stranded messenger RNA or mRNA performed by RNA polymerase. 
• The first step in transcription occurs , initiation. Where the DNA double helix structure is unwound by the RNA polymerase  in preparation for elongation
• The Second step in transcription is elongation.  This is the process of synthesising a premature mRNA strand. The RNA polymerase begins to create a complementary mRNA strand to the template strand. It moves along the template strand and synthesizes an RNA strand, making it longer as it moves along by joining free nitrogen bases in the nucleus to it.
• Then the third step is termination which takes place where the RNA polymerase reaches the stop sequence and stops the formation of the mRNA strand and exits the DNA strand to undergo splicing in the nucleus
• Splicing is the second main step in polypeptide synthesis. It is where the premature mRNA is turned into a mature mRNA. It does this by removing the non coding DNA or introns from the mRNA strand, and leaving the DNA that codes for Proteins  which  are called Exxon’s
• Translation is the third main step in polypeptide synthesis. The mRNA sequence is translated into a specific sequence of amino acids carried by transfer RNA or tRNA, which takes place in a ribosomes located in the cytoplasm. The tRNA transfers specific amino acids to the ribosome during formation of polypeptides.
• The first step In translation is initiation. Where the mRNA strand is prepared for translation.  The small ribosome subunits binds to the start of the mRNA strand at the codon and the large ribosome subunit binds to the tRNA in which carries the  anticodon, creating the “initiation complex” by joint the codon and anti codon
• The second step In translation is elongation,  where the polypeptide chain of amino acids is created when the tRNA brings a new amino acid one by one. The codon on the mRNA and the anti codon the tRNA donating the amino acids attract an and bind to each other. This forces the release of the amino acid into the cytoplasm. As a new amino acid is deposited, peptide bonds will form between them to form a chain.
• The final step in translation as well as the polypeptide synthesis process is termination. The ribosome will reach the stop codon, the release of amino acids  will stop as well as the formation of  the chain.
• After the polypeptide has been fully formed, it will travel back to the Golgi apparatus to become a protein.
• mRNA is need because DNA does not leave the nucleus. As a result, a message must be sent from the nucleus to the ribosomes where protein synthesis occurs to allow for proteins to be formed. This message is sent in the form of RNA.
• tRNA is needed because it has the molecule has a distinctive three loop structure that contains an anticodon and an amino acid. As a result of the complementary nature of the mRNA and tRNA codon-anticodon complex, the specific sequence of amino acids required for protein synthesis.