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Protein Synthesis

Protein Synthesis. Why do we need Proteins?. 1. Cell Structure Cell = 80% protein. Cell membrane. 2. Many Cell Processes are based on Proteins… Like Hormones (signals) Enzymes (speed up reactions) Membrane Channels (transport materials), and

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Protein Synthesis

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  1. Protein Synthesis

  2. Why do we need Proteins? 1. Cell Structure Cell = 80% protein Cell membrane 2. Many Cell Processesare based on Proteins… Like Hormones (signals) Enzymes (speed up reactions) Membrane Channels (transportmaterials), and Neurotransmitters(carry nerve / brain messages)

  3. Review of Proteins Protein Structure: Large molecules made up of thousands of amino acids The properties of the molecules are determined by: The type of the amino acids included The number of the amino acids used The order in which the amino acids are joined Protein Functions: As catalysts (enzymes) As antibodies As building materials (muscles) As hormones …And much, much more!

  4. Review of Nucleic Acids Nucleic acids made up of chains of nucleotides Nucleotides consist of: A base A sugar (ribose) A phosphate Two types of nucleic acids in cells: Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA)

  5. What are the differences between DNA & RNA? Two main differences: 1. Deoxyribonucleic acid (DNA) – “Double Helix” Ribonucleic acid (RNA) – “Single Strand” 2. Different Nucleotides Thymine in DNA Uracil in RNA

  6. What is needed for Protein Synthesis? Let’s think of Protein Synthesis like a Recipe…Such as Baking a Cake!! What is need for Protein Synthesis is like a Recipe’s Ingredients: (Instead of flour, sugar, eggs, etc., for a cake… 1. DNA (Deoxyribonucleic acid) 2. RNA (Ribonucleic acid) We will need three kinds (mRNA, tRNA, andrRNA) Messenger RNA (mRNA) - carries genetic information from DNA in nucleus to cytoplasm where proteins synthesized Transfer RNA (tRNA) - carries amino acids from amino acid pool to mRNA Ribosomal RNA (rRNA) - joins with ribosomal proteins in ribosome where amino acids joined to form protein primary structure. 3. Ribosomes 4. Amino Acids We will need 20 kinds (since there are 20 different amino acids)

  7. What are the Steps in Protein Synthesis? Now lets start “cookin’!”Following the analogy of a recipe…Here are the directions: (two main steps—like mixing dry ingredients and mixing other ingredients) Transcription- information transcribed from DNA into mRNA. Transcription (writing the “message”) DNA ►mRNA Translation - information in mRNA translated into a protein. Translation (reading the “message”) mRNA ►tRNA►protein (AA chain)

  8. What is Involved in “Transcription”? Codon is 3 bases long Information transcribed from DNA into RNA Location = nucleus Steps: The part of the DNA molecule (the gene) that the cell wants the information from to make a protein unwinds to expose the bases. Enzyme binds to DNA, unzips it. The mRNA copy is made with the help of RNA polymerase. This enzyme joins up the mRNA nucleotides to make a mRNA strand. This mRNA strand is a complementary copy of the DNA (gene) Free mRNA nucleotides in the nucleus base pair with one strand of the unwound DNA molecule. mRNA copy of gene made from DNA template*U replaces T in RNA The mRNA molecule leaves the nucleus via a nuclear pore into the cytoplasm The mRNA moves to ribosome and DNA helix rewinds

  9. What is Involved in “Translation”? Information TranslatedfrommRNA ►tRNA►protein (AminoAcidchain) Location = cytoplasm (1st) then ribosome (2nd) (NOTE: first codon in mRNA is the start codon AUG) Information in mRNA translated into primary sequence of a protein in 4 steps: ACTIVATION INITIATION ELONGATION TERMINATION (Animation on teacherworld.com)

  10. What is Involved in “Translation”? Information in mRNA translated into primary sequence of a protein in 4 steps: ACTIVATION INITIATION ELONGATION TERMINATION ACTIVATION 1. tRNA molecules are activated as tRNAsynthetase enzyme attaches their complementary amino acids to them.

  11. What is Involved in “Translation”? Information in mRNA translated into primary sequence of a protein in 4 steps: ACTIVATION INITIATION ELONGATION TERMINATION INITIATION 1. mRNA copy attaches to the small subunit of the ribosome in cytoplasm. 6 of the bases in the mRNA are exposed in the ribosome. 2. tRNAanticodon UAC bringsAA(methionine)to mRNA codon on ribosome 3. Initiator tRNA attaches to start codonA tRNA bonds complementarily with the mRNA via its anticodon. 4. Larger body of ribosome combines with smaller body.

  12. What is Involved in “Translation”? Information in mRNA translated into primary sequence of a protein in 4 steps: ACTIVATION INITIATION ELONGATION TERMINATION ELONGATION 1. A second tRNA bonds with the next three bases of the mRNA, the amino acid links onto the amino acid of the first tRNA via a peptide bond. (Reminder) Each tRNA specific for one amino acid only, but some amino acids coded for by up to 6 codons. Order of bases in mRNA codons determine which tRNA anticodons will align and therefore determines order of amino acids in protein 2. The ribosome moves along one codon (3 bases long). (The first tRNA leaves the ribosome.) 3. A third tRNA brings a third amino acid. 4. Ribosome moves down mRNA to next codon 5. tRNA anticodon brings & attaches next AA with peptide bond.

  13. What is Involved in “Translation”? Information in mRNA translated into primary sequence of a protein in 4 steps: ACTIVATION INITIATION ELONGATION TERMINATION TERMINATION 1. Eventually a stop codon is reached on the mRNA This final codon on mRNA contains termination signal 2. Releasing factors cleave polypeptide chain from tRNA that carried final amino acid.The newly synthesised polypeptide leaves the ribosome. 3. mRNA is released from ribosome and broken down into nucleotides.

  14. Summary Protein synthesis is an essential part of our body! Proteins are long chains of amino acids which serve many roles, from enzymes, to the basic structural unit of our cells. Protein synthesis involves not only amino acids, but nucleic acids and ribosomes as well. Protein synthesis can be likened to a recipe, with ingredients and directions for preparing the “protein cake”!

  15. Transcription Translation

  16. Protein Synthesis Process

  17. Activity Making a Recipe Card for Protein Synthesis Use your notes and the 4 by 6 index card I gave to you to write your own “recipe card”. Recipe Name Ingredient List Directions 1. 2.

  18. References http://staffweb.psdschools.org/shunter/Bioweb/DNA%20Protein%20Synth/Protein%20Synthesis.pdf www.worldofteaching.com/powerpoints/biology/protein%20synthesis.ppt www.unisanet.unisa.edu.au/.../Lecture%20Presentation%20-%20Protein%20Synthesis.ppt

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