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Protein Synthesis

Protein Synthesis. Grade 12 Earl Haig. Why do we need to synthesize proteins? What important roles do they play?. Examples of Protein Function. Protein Synthesis. Proteins are the machines that make all living things function. They are VERY important

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Protein Synthesis

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  1. Protein Synthesis Grade 12 Earl Haig

  2. Why do we need to synthesize proteins? What important roles do they play?

  3. Examples of Protein Function

  4. Protein Synthesis • Proteins are the machines that make all living things function. They are VERY important • Proteins perform specific functions within cells. • DNA codes for these proteins • DNA is the blue print for making proteins • What is a blue print? • DNA CANNOT LEAVE THE NUCLEUS • Why is this? • However Proteins are made in the cytoplasm! • How does the information from the DNA get sent to the cytoplasm to make proteins?

  5. This is how! DNA is transcribed (a copy is made) into a complementary RNA message that can code for genetic material Numerous copies of this message can be delivered to Ribosomes in the cytoplasm that translate the message into polypeptide chains which are processed into proteins

  6. 2 Processes • Transcription • Making a copy of the code • Translation • Translating code into another language, amino acids

  7. RNA (Ribonucleic Acid) • Carrier of genetic information • Single Stranded but can complimentarily pair with itself • 3 types • Ribosomal RNA • Structural component of a ribosome • Transfer RNA (tRNA) • Transfers the amino acids to the ribosome to build a protein • Messenger RNA (mRNA) • Varies in length depending on the gene • Important for Transcription

  8. What is the difference between DNA and RNA?

  9. Differences b/w RNA and DNA • Instead of Thymine, RNA uses Uracil which complimentarily pairs with Adenine (AU) • Ribose sugar instead of Deoxyribose sugar

  10. Similarly to DNA, RNA free nucleotides have 3 phosphate groups • When they bind on to the growing RNA strand, they lose 2 phosphate groups

  11. Transcription Transcription is the process of making an RNA copy of a gene sequence (DNA). This copy, called a messenger RNA (mRNA) molecule The mRNA made during transcription leaves the cell nucleus and enters the cytoplasm, where it directs the synthesis of the protein that it encodes (Translation).

  12. Transcription • mRNA production during transcription requires the use of DNA as a template

  13. Transcription (Part 1) • Initiation • RNA Polymerase binds the DNA at a specific site called “The Promoter” • The Promoter • Tells RNA Polymerase where to start transcribing and what strand to transcribe • Upstream of a gene coding a specific protein • High in Adenine & Thymine • TATAAA box • The promoter itself is not transcribed

  14. Transcription (Part 2) • Elongation: • Using DNA as a template, RNA Polymerase puts together appropriate Ribonucleotides and builds the mRNA transcript in the 5’3’ direction. • Unlike DNA Replication, no primer is needed for RNA Polymerase to start building the complimentary strand • Complementary base pairing • Adenine & Uracil • Guanine & Cytosine • DNA strand NOT being used for transcription = Coding Strand • DNA strand being used for transcription = Template Strand • mRNA is complementary to the template strand, therefore identical to the coding strand except the T and U are switched

  15. Transcription (Part 3) • Termination • RNA Polymerase continues to synthesize mRNA until it passes the end of the gene • There is a Terminator Sequence that is recognized by the enzyme • mRNA is released from the DNA and exits the nucleus for Translation

  16. http://www.youtube.com/watch?v=ztPkv7wc3yU

  17. TRY THIS AT HOME! http://www.pbslearningmedia.org/resource/lsps07.sci.life.stru.celltrans/cell-transcription-and-translation/

  18. Post-Transcriptional Modifications • In eukaryotic cells, the primary transcript of mRNA must be modified before it can leave the nucleus • Capping: • A 5’ cap is added • This cap protects mRNA from digestion by nucleases and phosphatases as it exits the nucleaus and enters the cytoplasm • Consists of modified guanine nucleoside triphosphate • Plays a role in the initiation of translation

  19. Post-Transcriptional Modifications • Tailing: • a string of about 200 adenine ribonucleotides is added to the 3’ end of the mRNA • AKA Poly-A Tail • Added by the enzym Poly-A polymerase

  20. Post Transcriptional Modifications DNA of eukaryotic genes contain coding regions (exons) and non-coding regions (introns) If the non-coding regions are translated, the resulting protein will not fold correctly Introns are removed from the primary transcript or pre-RNA before it leaves the nucleus Spliceosomes cut out the introns and join the remaining exons so that the mRNA is comprised of only coding regions. This exits the nucleus and the remainng introns stay in the nucleus and it’s nucleotides are recycled

  21. Post Transcriptional Modifications Ctd… There is no quality control enzyme to make sure the mRNA transcript is correct BUT… Because there are hundreds of transcripts being made consistently of the same gene for protein synthesis, if a protein made from one mRNA transcript degrades, there are lots of other correct copies that can compensate for this loss

  22. Overview Video Clip • http://i-biology.net/ibdpbio/01-cells-and-energy/transcription-and-translation-inc-ahl-73-74/ • Finishes at 7:32

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