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Protein Synthesis

Protein Synthesis. Today we will be learning about how proteins are made. What do you guys already know about making proteins?. Transcription Introduction Animation. Protein Synthesis: The making of proteins from DNA DNA  mRNA  polypeptides. Transcription. Translation.

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Protein Synthesis

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  1. Protein Synthesis • Today we will be learning about how proteins are made What do you guys already know about making proteins? Transcription Introduction Animation

  2. Protein Synthesis: The making of proteins from DNADNA  mRNA  polypeptides Transcription Translation

  3. Review Slide: What is DNA Made Of? • DNA is made of 4 different bases • They come in pairs • Cytosine and Guanine, Adenine and Thymine Who can tell me about complementary base pairing?

  4. What is RNA Made Of? • RNA is composed of nucleotides • RNA is single stranded • It is made of 4 bases • Instead of Thymine, RNA has Uracil.

  5. DNA versus RNA

  6. Goal of Transcription The goal of transcription is to make a mRNA (messenger RNA) strand inside the nucleoplasm that can move into the cytoplasm to be read

  7. Transcription Animation

  8. Transcription Process 1. DNA unzips using the enzyme RNA polymerase 2. The promoter is a sequence of nucleotides that signals for the beginning of the transcription process (this is found on the antisense strand of DNA)

  9. Transcription Process 3. RNA nucleotides in the nucleoplasm complementary base pair with one strand of the DNA molecule 4. The new nucleotides are bonded together by the enzyme RNA polymerase (this period is called elongation) Important Note: Just like in DNA replication, new nucleotides are added to the 3’ side

  10. 5. The transcription process moves along the DNA strand until it hits a terminator sequence 6. The mRNA completely separates and now there is a single strand of mRNA Note: the mRNA strand is shorter than the DNA strand because it is encoded for one gene and is typically the length required to make one polypeptide

  11. How does this change for Eukaryotic Cells? • Note: What we just learned is the simplified version of Transcription for Prokaryotic Cells • Eukaryotic Cell adjustments: • Some of the mRNA is non-coding (called introns) and needs to be removed to form mature mRNA (so only the exons are left) before Translation Comparing Prokaryotic and Eukaryotic Protein Synthesis

  12. DNA Translation • DNA translation is the process that converts an mRNA sequence into a string of amino acids that form a protein http://www.dnalc.org/resources/3d/TranslationBasic_withFX0.html

  13. Translation Process • mRNA that is now in the cytosplasm will locate a ribosome and align with it so that the start codon can be read • Codons – a set of three bases in a row on a mRNA molecule; when the codon is read by tRNA (transfer RNA) it codes for a specific amino acid to be made

  14. 2. A specific tRNA molecule floats in; the tRNA molecule must have the complementary anticodon to the first mRNA codon

  15. Amino acid is here! • A tRNA molecule has an anticodon at one end and an amino acid on the other

  16. 3. Another tRNA molecule brings in the next set of anticodons to bond with the mRNA codon 4. Now, two amino acids are side by side so an enzyme catalyzes the reaction to bond them together covalently (this makes a peptide bond) 5. The first tRNA molecule can now detach from the amino acid and move out into the cytoplasm to search for another amino acid to join with

  17. 6. This process continues until the ribosome reaches the stop codon; this will signal the end of translation 7. The entire polypeptide now breaks away from the final tRNA molecule and becomes a free-floating polypeptide in the cytoplasm

  18. One Gene/One Polypeptide • In the early 1940’s people hypothesized that for every one gene of DNA produced, one protein was produced • It was later discovered that many proteins are composed of more than one polypeptide and it was proposed that each individual polypeptide required a separate gene • In the last few years, researchers have discovered that one gene results in the production of many different polypeptides during translation since mRNA molecules can be modified in different ways

  19. Protein Synthesis Video

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