protein synthesis

• RNA

  ribonucleic acid
• The sugar in the RNA nucleotide

  ribose
• Nitrogen bases for RNA

  adenine, uracil, guanine, cytosine
• Protein synthesis


  the process of decoding DNA and making a protein
• Genes


  section of DNA that codes the production of a specific protein
• What determines your traits

  the sequence of amino acids
• Transcription


  RNA polymerase copies the sequence of nucleotides in DNA to make MRNA (messenger RNA)
• Transcription process happens

  inside the nucleus
• Adenine-Uracil

  A-U
• Guanine-Cytosine


  G-C
• RNA Polymerase


  Joins RNA nucleotides to create MRNA
• Translation


  the process of decoding mRNA into amino acids and making a polypeptide (protein)
• mRNA to Proteins (language is changing)

  translation
• What process happens inside the ribosome

  Translation
• Steps of translation

  1. mRNA moves from nucleus to ribosome

  2. mRNA attaches to rRNA (ribosome)

  3. tRNA (transfer RNA) brings a specific amino acid to the ribosome

  4 tRNA's amino acids attach to each other forming a protein
• Codon


  3 nucleotide/base code for an amino acid on mRNA
• Anti-codon


  3 nucleotide/base code for an amino acid on tRNA
• Gene


  A section of DNA with a particular sequence of bases that codes for a particular sequence of amino acids
• Codon


  A sequence of three bases that is the code for a single specific amino acid
• Polypeptide chain


  The amino acid sequences that are joined together to form a protein
• Proteins


  • They fold up into a unique shape which enables them to fulfil a specific function
  • Types: Enzymes, Hormones, Structural proteins
• Protein synthesis


  1. Transcription (DNA is transcribed and an mRNA molecule is produced)

  2. Translation (mRNA is translated and a polypeptide chain is produced)
• The order of bases in the DNA determines which proteins are produced
• Enzymes


  Speed up chemical reactions occurring in the body
• Hormones


  Proteins that carry messages around the body
• Structural proteins


  Proteins that provide structure and are physically strong
• There are also many other types of proteins
• Gene


  A sequence of nucleotide bases in a DNA molecule that codes for the production of a specific sequence of amino acids, that in turn make up a protein
• Transcription


  DNA is transcribed and an mRNA molecule is produced
• Translation


  mRNA (messenger RNA) is translated and an amino acid sequence is produced
• Transcription


  • Occurs in the nucleus of the cell
  • Part of a DNA molecule unwinds (the hydrogen bonds between the complementary base pairs break)
  • This exposes the gene to be transcribed
  • An enzyme known as RNA polymerase binds to a region of non-coding DNA just in front of the gene
  • RNA polymerase then makes a complementary copy of the code from the gene by building a single-stranded nucleic acid molecule known as mRNA (messenger RNA)
  • The mRNA molecule leaves the nucleus via a pore in the nuclear envelope
• RNA


  • A polynucleotide - it is made up of many nucleotides linked together in a long chain
  • Contains the nitrogenous bases adenine (A), guanine (G) and cytosine (C), but never thymine (T) - instead it contains uracil (U)
  • RNA molecules are only made up of one polynucleotide strand (they are single-stranded)
• Translation


  • Occurs in the cytoplasm of the cell
  • The mRNA molecule attaches to a ribosome
  • The ribosome 'reads' the code on the mRNA in groups of three (each triplet of bases on the mRNA molecule, known as a codon, codes for a specific amino acid)
  • In this way, the ribosome translates the sequence of bases into a sequence of amino acids that make up a protein
  • tRNA molecules have a triplet of unpaired bases at one end (the anticodon) and a region where a specific amino acid can attach at the other
  • There are at least 20 different tRNA molecules, each with a specific anticodon and specific amino acid binding site
  • The tRNA molecules bind with their specific amino acids (also in the cytoplasm) and bring them to the mRNA molecule on the ribosome
  • The triplet of bases (anticodon) on each tRNA molecule pairs with a complementary triplet (codon) on the mRNA molecule
  • Two tRNA molecules fit onto the ribosome at any one time, bringing the amino acid they are each carrying side by side
  • A peptide bond is then formed between the two amino acids
  • This process continues until a 'stop' codon on the mRNA molecule is reached - this acts as a signal for translation to stop and at this point the amino acid chain coded for by the mRNA molecule is complete
  • This amino acid chain (the final polypeptide) will then fold to form a protein
• DNA cannot travel out of the nucleus to the ribosomes (it is far too big to pass through a nuclear pore) so the base code of each gene is transcribed into an RNA molecule called messenger RNA (mRNA)