Protein Synthesis

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Protein Synthesis

• Transcription Translation

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RNA is composed of 3 parts

• Ribose smaller sugar than deoxyribose of DNA
• Phosphate
• 4 Nitrogenous Bases
• Adenine (A)
• Guanine (G)
• Uracil (U) instead of T
• Cytosine (C)
• RNA is single stranded and thus smaller able to
  leave the nucleus of the cell

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• These 3 parts (deoxyribose, phosphate and 1 base)
  still form a nucleotide when combined
• RNA is used by DNA to carry the code and create
  proteins that control the functioning of the cell
• There are several types of RNA used mRNA and
  tRNA.

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TranscriptionWriting of DNA Message to mRNA

• Takes places in the nucleus of the cell
• The process by which the information from DNA is
  transferred to RNA.
• DNA uncoils and unzips.
• The exposed DNA bases are matched up with RNA
  bases in the nucleus to form mRNA.

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mRNA (Messenger RNA)

• The mRNA will detach and because it is
  single-stranded relatively small, it can move
  out of the nucleus into the cell cytoplasm.
• The DNA strands rejoin.
• The mRNA will move to the ribosomes with the DNA
  message.

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Translation

• In the cytoplasm, translation occurs.
• The mRNA binds to a ribosome.
• The strand of mRNA is pulled through the ribosome
  three bases at a time, in triplets.

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• Each of these triplets on the mRNA strand is
  called a codon.

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tRNA (Transfer RNA)

• Transfer RNA (tRNA), reads the strand of mRNA and
  translates it into a strand of amino acids.
• A molecule of tRNA has at one end a set of three
  bases that will complement the mRNA strand this
  is called the anticodon.
• At the other end is a specific amino acid.
• If the 3 base anticodon of the tRNA complements
  the 3 base codon of the mRNA, they briefly
  combine.
• The amino acid is left behind when the tRNA
  leaves.
• As each codon is read, the next tRNA brings in a
  new amino acid and the polypeptide (protein)
  chain grows.
• This requires enzymes and ATP.

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Codons code for particular amino acids

• Each codon will correspond to one amino acid.
• These amino acids when put together form
  polypeptides or proteins.
• The genetic code is redundant. There are 64
  possible codons but only 20 amino acids.

 
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Translation






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