PROTEIN SYNTHESIS

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PROTEIN SYNTHESIS
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PROTEIN SYNTHESIS

• Process of using DNA to make protein
• Function of protein in body
• Enzymes
• Immunity
• Communication between cells
• structural
• Characteristics (skin color, eye color, etc)

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Structure of DNA

• Double helix
• Nucleotides
• Dexyribose (5 carbon sugar)
• Phosphate
• Nitrogen base (A,T,C,G)

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DNA
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DNA
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BASES
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HELPERS

• RNA - ribonucleic acid
• Single strand of nucleotides
• Can act as a messenger between DNA and ribosomes
• Ribosomes - where protein is constructed
• 3 types of RNA
• mRNA
• tRNA
• rRNA

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3 Stages of Protein synthesis

• 1. Transcription - write recipe down
• 2. Translation - put recipe together
• 3. Elongation - glue amino acids together to
  form protein

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SUMMARY
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Transcription

• Occurs in nucleus of cell
• Process by which molecule of DNA is copied into
  complementary strand of mRNA

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Steps of Transcription

• 1. DNA unwinds and unzips (helicase) (only in
  area of the recipe) creating 2 strands. An
  active strand and dummystrand
• 2. Active strand is the one to be used to make
  the protein (the template)
• 3. Special sequence of DNA is recognized by RNA
  polymerase as the start signal (promoter)

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Steps of transcription cont

• 4. RNA polymerase matches up complementary bases
  between DNA and RNA (A-U, C-G), using DNA as a
  template
• 5. RNA polymerase moves along the area of the DNA
  with the recipe, matching up complementary bases
  (elongation phase)
• 6. when it hits the stop codon mRNA drops off
  DNA.(termination phase)
• 7. At this point mRNA has copied the recipe
  for the protein.
• DNA winds back up and mRNA gets modified before
  leaving the nucleus

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(No Transcript)
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TRANSCRIPTION
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mRNA modification

• While still in the nucleus, mRNA gets modified.
• mRNA consists of exons and introns
• An enzyme comes along and splices out the introns
  (pieces of DNA) that is not part of the recipe
  needed for the protein.
• Exons are then spliced together to create the
  real recipe for the protein your body needs
• Exons are capped and tailed for protection and
  then leave the nucleus via nuclear pores.

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EXONS AND INTRONS
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WHY COPY DNA????

• DNA is too large to leave the nucleus, so it
  needs a messenger to bring genetic information to
  the ribosome in the cytoplasm.
• This messenger is the mRNA

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TRANSLATION

• Process of decoding mRNA into protein
• Code being translated from language of nucleic
  acids into polypeptide

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STEPS OF TRANSLATION

• 1. mRNA attaches onto a ribosome and the first
  codon start is read by the ribosome. This
  signals ribosome to start translating the recipe
  (initation phase)
• 2. The ribosome reads each codon of mRNA and
  signals tRNA (complementary nitrogen bases which
  are carrying a specific amino acid. (Also called
  an anticodon)
• 3. Complementary tRNA matches up with mRNA codon,
  and brings the amino acid along with it.

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IN THE CYTOPLASM
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Translation cont.

• 4. The ribosome moves along the mRNA reading it
  and signaling tRNA to bring amino acids to the
  ribosome.
• 5. The amino acids are bonded together, the
  previous one with the next one in line.
  (elongation)
• 6. This continues until the ribosome hits the
  stop codon. (terminiation)
• 7. When hits stop codon, mRNa breaks off and
  returns to the nucleus (disassembles)
• 8. All that is left is a string of amino acids
  in a specific order. This specific order is what
  determines the name and type of protein that was
  just made.

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TRANSLATION ON RIBOSOME
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TRANSLATION
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Translation
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ELONGATION

• The string of amino acids is bonded together
  (during the process of translation) to create the
  protein that your body needs.

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