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Protein Synthesis Chapter 10
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Imagine Imagine you were a cell and your job was to make proteins.
How would you do it? What would you use? Where do you start? Is there anyone or anything that could help you?
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What are proteins? Quick Review Proteins are biological molecules made of amino acids.
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Amino Acids Amino acids play central roles both as building blocks of proteins and as intermediates in metabolism.
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The cell’s job is…. It is the cell’s job to make proteins.
The instructions that the cell needs to make proteins are kept (coded) in the genes located in our DNA.
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Genetic Library Your DNA can be compared to a very large library, full of thousands upon thousands of cook books. Directions for making proteins can be found on a single page of one cook book, or a couple of pages, or maybe even an entire chapter- depending on the protein being made and the length of the gene coding its instructions.
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So, how do we get from here…
DNA protein …to here?
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DNA RNA copy
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How Genes Work Genes are coded DNA instructions (aka recipes) that control the production of proteins with in the cell. The first thing that needs to happen is for DNA to be copied into RNA. Now the RNA contains the coded information (recipe) for making proteins.
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A = U C = G RNA ribonucleic acid Base Pairs contains the sugar ribose
uses uracil instead of thymine is single stranded usually much shorter in length than DNA about the length of one gene Base Pairs A = U C = G Think of RNA as j-U-nk DNA
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RNA vs. DNA RNA DNA Single-stranded molecule in most of its biological roles and has a much shorter chain of nucleotides. Contains ribose Complementary nucleotide to adenine is uracil Double-stranded helix Contains deoxyribose Complementary nucleotide to adenine is thymine
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The many faces of RNA Messenger RNA (mRNA): carries copies of instructions for assemble of amino acids into proteins from DNA to the rest of the cell Ribosomal RNA (rRNA): makes up the major part of the ribosome Transfer RNA (tRNA): transfers amino acids to ribosomes during protein synthesis
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Making j-U-nk copies of DNA
Transcription Making j-U-nk copies of DNA
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RNA & Transcription During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled.
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The Genetic Code mRNA has a “4” letter alphabet:
U C G “words” (codes) are only 3 letters long each 3 letter “word” is called a codon
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TRANSLATING THE “MESSAGE” INTO A PROTEIN
TRANSLATION TRANSLATING THE “MESSAGE” INTO A PROTEIN
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How is the “message” read?
mRNA tRNA tRNA reads the “words” using a lock-and-key method: ANTICODON “word”
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How is the “message” read?
Start codon: AUG mRNA: indicates where translation should begin Stop codons: UAA, UAG, UGA Signal for translation to end
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UCGCACGGU UCG – CAC - GGU Serine-Histidine-Glycine
The Genetic Code UCGCACGGU UCG – CAC - GGU Serine-Histidine-Glycine
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Translation Decoding of a mRNA message into a polypeptide chain of amino acids or a protein Takes place on the ribosomes. DNA replication RNA transcription mRNA translation protein
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Summary
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