Protein Synthesis PDF

copyright cmassengale 1  Protein Synthesis DNA ‘s code must be copied and taken to the ribosomes. In the ribosomes, this code must be read so amino acids (20) can be assembled to make polypeptides and eventually proteins. This process is called PROTEIN SYNTHESIS akA The Central Dogma...

copyright cmassengale 1  Protein Synthesis DNA ‘s code must be copied and taken to the ribosomes. In the ribosomes, this code must be read so amino acids (20) can be assembled to make polypeptides and eventually proteins. This process is called PROTEIN SYNTHESIS akA The Central Dogma copyright cmassengale 2  Roles of RNA and DNA DNA is the MASTER PLAN RNA is the BLUEPRINT (copy) of the Master Plan (can leave the nucleus); also has other functuons… copyright cmassengale 3  DNA Begins the Process DNA is found inside the nucleus Proteins, however, are made in the cytoplasm of cells by organelles called ribosomes Ribosomes may be free in the cytosol or attached to the surface of rough ER copyright cmassengale 4 RNA Differs from DNA RNA has a sugar ribose DNA has a sugar deoxyribose copyright cmassengale 5  Other Differences RNA contains the base uracil (U) DNA has thymine (T) RNA molecule is single- stranded DNA is double-stranded DNA copyright cmassengale 6 Structure of RNA copyright cmassengale 7 Remember the Complementary Bases On DNA: A-T C-G On RNA: A-U C-G copyright cmassengale 8. Three Types of RNA Messenger RNA (mRNA) copies DNA’s code & carries the genetic information to the ribosomes Ribosomal RNA (rRNA), along with protein, makes up the ribosomes Transfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesized copyright cmassengale 9 Messenger RNA Long Straight chain of Nucleotides Made in the Nucleus Copies DNA & carries info to ribosomes. copyright cmassengale 10 Ribosomal RNA (rRNA) Globular in shape Are part of the ribosomes actual structure. Site of protein Synthesis (where the proteins are made) copyright cmassengale 11  Transfer RNA (tRNA) Clover-leaf shape Single stranded molecule. Attachment site at one end for an amino acids. Opposite end has three nucleotide bases called the anticodon. copyright cmassengale 12 Transfer RNA amino acid attachment site U A C anticodon copyright cmassengale 13  Codons and Anticodons Groups of 3 nucleotides are called Codons The 3 bases of an anticodon are UGA complementary to the 3 bases of a codon Example: Codon ACU ACU Anticodon UGA copyright cmassengale 14 The Genetic Code A codon designates an amino acid An amino acid may have more than one codon There are 20 amino acids, but 64 possible codons Some codons tell the ribosome to stop translating copyright cmassengale 15 The Genetic Code Use the code by reading from the center to the outside Example: AUG codes for Methionine copyright cmassengale 16 Name the Amino Acids GGG? UCA? CAU? GCA? AAA? copyright cmassengale 17  The Central Dogma of Biology = going from a DNA code to a protein. Two Steps: 1) Transcription 2)Translation copyright cmassengale 18  Transcription – makes mRNA The process of copying the sequence of one strand of DNA, the template strand. During transcription, RNA polymerase binds to DNA and separates the DNA strands RNA Polymerase then uses one strand of DNA as a template to assemble nucleotides into RNA copyright cmassengale 19 Transcription Promoters are regions on DNA that show where RNA Polymerase must bind to begin the Transcription of RNA Called the TATA box. copyright cmassengale 20 Transcription Specific base sequences act as signals to stop Called the termination signal. Once the Polymerase is done it falls off, the DNA re-zips up and the mRNA escapes out the nucleus. copyright cmassengale 21 mRNA Transcript mRNA leaves the nucleus through its pores and goes to the ribosomes. copyright cmassengale 22 Translation Translation is the process of decoding the mRNA into a protein. Ribosomes read mRNA three bases or 1 codon at a time and construct the proteins Methionine (AUG) on mRNA is called the start codon because it triggers the linking of amino acids copyright cmassengale 23 Ribosomes Made of a large and small subunit Composed of rRNA (40%) and proteins (60%) Have two sites for tRNA attachment --- P and A copyright cmassengale 24 Step 1- Initiation mRNA enters the ribosome and attaches to the tRNA. The tRNA has an anticodon that matches with the three “start” nucleotides. 25  Initiation aa2 amino 2-tRNA 1-tRNA G A U anticodon U A C hydrogen A U G C U A C U U C G A bonds codon mRNA copyright cmassengale 26  Step 2 - Elongation The ribosome moves down the mRNA strand. The first tRNA detaches and leaves it’s amino acid. Two new tRNA with their amino acids move into position (positions are called A and P) The new tRNAs have the correct amino acid for that specific codon. Each amino Acid forms a bond. copyright cmassengale 27  Amino peptide bonds 1 Amino 4 Amino Amino 2 3 4-tRNA 2-tRNA 3-tRNA G C U G A U G A A A U G C U A C U U C G A A C U mRNA copyright cmassengale 28 Amino peptide bonds Amino 1 Amino 5 2 Amino 4 Amino 3 5-tRNA U G A 3-tRNA 4-tRNA G A A G C U G C U A C U U C G A A C U mRNA copyright cmassengale 29 Termination tRNA’s will continue to read mRNA and hook up amino acids until “stop” codon is reached. A “stop” codon is three nucleotides on the mRNA that tRNA does not have an anticodon for. copyright cmassengale 30 Dissaembly When the stop codon is reached the ribosome falls off, the protein goes into the body, and the tRNAs go out to find more amino acids. The ribosome will go find another strand of mRNA and the whole process starts over. 31 End Product –The Protein! The end products of protein synthesis is a primary structure of a protein A sequence of amino acid bonded together by peptide bonds 5 3 4 2 199 1 200 copyright cmassengale 32