PROTEIN SYNTHESIS copyright cmassengale 1 DNA DNA contains

PROTEIN SYNTHESIS copyright cmassengale 1

DNA • DNA contains genes, sequences of nucleotide bases • These Genes code for polypeptides (proteins) • Proteins are used to build cells and do much of the work inside cells copyright cmassengale 2

Amino Acid Structure copyright cmassengale 3

Polypeptides • Amino acid chains are called polypeptides copyright cmassengale 4

Starting with DNA • DNA ‘s code must be copied and taken to the cytosol • In the cytoplasm, this code must be read so amino acids can be assembled to make polypeptides (proteins) • This process is called PROTEIN SYNTHESIS copyright cmassengale 5

Pathway to Making a Protein DNA m. RNA Read by ribosomes Protein copyright cmassengale 6

DNA RNA Protein Eukaryotic Cell Nuclear membrane DNA Transcription Pre-m. RNA Processing m. RNA Ribosome Translation Protein copyright cmassengale 7

RNA copyright cmassengale 8

Differences between DNA and RNA Nucleic Sugar Base Strands Acid DNA Deoxyrib A, C, G, Double ose Thymine RNA Ribose A, C, G, Uracil copyright cmassengale Single 9

Structure of RNA copyright cmassengale 10

. Three Types of RNA • Ribosomal RNA (r. RNA), along with protein, makes up the ribosomes • Messenger RNA (m. RNA) copies DNA’s code & carries the genetic information to the ribosomes • Transfer RNA (t. RNA) transfers amino acids to the ribosomes where proteins are synthesized copyright cmassengale 11

Ribosomal RNA (r. RNA) • r. RNA is a single strand 100 to 3000 nucleotides long • Globular in shape • Made inside the nucleus of a cell and exported to cytoplasm • Associates with proteins to form ribosomes • Site of protein Synthesis copyright cmassengale 12

Messenger RNA • Long Straight chain of Nucleotides • Copies DNA and carries the information for a specific protein • Made up of 500 to 1000+ nucleotides long, organized into 3 -base codons copyright cmassengale 13

Remember the Complementary Bases On DNA: A-T C-G On RNA: A-U C-G copyright cmassengale 14

Genetic Code § DNA contains a triplet code § Every three bases on DNA stands for ONE amino acid § Each three-letter unit on m. RNA is called a codon § Most amino acids have more than one codon! § 20 amino acids: 64 different triplets § ALL organisms use the SAME code 15

The Genetic Code • Example: AUG codes for Methionine 16

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Transfer RNA (t. RNA) • Clover-leaf shape • Single stranded molecule with attachment site at one end for an amino acid • Opposite end has three nucleotide bases called the anticodon copyright cmassengale 18

Transfer RNA amino acid attachment site U A C anticodon copyright cmassengale 19

Codons and Anticodons • The 3 bases of an anticodon are complementary to the 3 bases of a codon • Example: Codon ACU Anticodon UGA copyright cmassengale UGA ACU 20

RNA Ad • You are part of a marketing team tasked with designing a half page ad to sell RNA. You need to have a picture and slogan that will sell at least one of the types of RNA to consumers by showcasing its unique properties. • Underneath your ad, write 3 -5 sentences explaining how your ad will sell RNA. copyright cmassengale 21

Two Parts of Protein Synthesis § Transcription makes an RNA molecule complementary to a portion of DNA § Translation occurs when the sequence of bases of m. RNA DIRECTS the sequence of amino acids in a polypeptide 22

Transcription Translation 23

Transcription • The process of copying the sequence of one strand of DNA, the template strand • m. RNA copies the template strand • Requires the enzyme RNA Polymerase copyright cmassengale 24

Template Strand copyright cmassengale 25

Question: § What would be the complementary RNA strand for the following DNA sequence? DNA 5’-GCGTATG-3’ copyright cmassengale 26

Answer: • DNA 5’-GCGTATG-3’ • RNA 3’-CGCAUAC-5’ copyright cmassengale 27

Transcription • 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 28

RNA Polymerase copyright cmassengale 29

m. RNA Transcript • m. RNA leaves the nucleus through its pores and goes to the ribosomes copyright cmassengale 30

Translation • Translation is the process of decoding the m. RNA into a polypeptide chain • Ribosomes read m. RNA three bases or 1 codon at a time and construct the proteins copyright cmassengale 31

Ribosomes • Made of a large and small subunit • Composed of r. RNA (40%) and proteins (60%) • Have two sites for t. RNA attachment --- P and A copyright cmassengale 32

Translation • Three steps: 1. initiation: m. RNA binds to ribosome at start codon (AUG) 2. elongation: amino acids linke 3. termination: stop codon (UAG, UAA, or UGA) signals ribosome to release m. RNA 33

Step 1 - Initiation • m. RNA transcript attaches to the small ribosomal subunit • Small subunit attaches to large ribosomal subunit m. RNA transcript copyright cmassengale 34

Ribosomes Large subunit P Site A Site m. RNA Small subunit A U G C U A C U U C G copyright cmassengale 35

Initiation aa 2 aa 1 2 -t. RNA 1 -t. RNA anticodon hydrogen bonds U A C A U G codon G A U C U A C U U C G A copyright cmassengale m. RNA 36

Step 2 - Elongation • As ribosome moves, t. RNA with their amino acids move into the ribosome • Peptide bonds join the amino acids copyright cmassengale 37

Elongation peptide bond aa 1 aa 3 aa 2 3 -t. RNA 1 -t. RNA anticodon hydrogen bonds U A C A U G codon 2 -t. RNA G A U C U A C U U C G A copyright cmassengale m. RNA 38

aa 1 peptide bond aa 3 aa 2 1 -t. RNA 3 -t. RNA U A C (leaves) 2 -t. RNA A U G G A A G A U C U A C U U C G A m. RNA copyright cmassengale Ribosomes move over one codon 39

aa 1 peptide bonds aa 2 aa 4 aa 3 4 -t. RNA 2 -t. RNA A U G 3 -t. RNA G C U G A A C U U C G A A C U m. RNA copyright cmassengale 40

aa 1 peptide bonds aa 4 aa 2 aa 3 2 -t. RNA 4 -t. RNA G A U (leaves) 3 -t. RNA A U G G C U G A A C U U C G A A C U m. RNA copyright cmassengale Ribosomes move over one codon 41

aa 1 peptide bonds aa 5 aa 2 aa 3 aa 4 5 -t. RNA U G A 3 -t. RNA 4 -t. RNA G A A G C U A C U U C G A A C U m. RNA copyright cmassengale 42

peptide bonds aa 1 aa 5 aa 2 aa 3 aa 4 5 -t. RNA U G A 3 -t. RNA G A A 4 -t. RNA G C U A C U U C G A A C U m. RNA copyright cmassengale Ribosomes move over one codon 43

aa 4 aa 5 Termination aa 199 aa 3 primary structure aa 2 of a protein aa 200 aa 1 200 -t. RNA A C U terminator or stop codon C A U G U U U A G m. RNA copyright cmassengale 44

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 aa 2 aa 1 aa 3 aa 4 aa 5 aa 199 copyright cmassengale aa 200 45