Protein Synthesis
If DN resides in the nucleus, and proteins are made at the ribosomes, how can DN direct protein production? cell nucleus? ribosome
Summary of Protein Synthesis DN deoxyribonucleic acid Important Note: Step 1: Transcription inside nucleus DN is the cell s official, permanent source of information. It never leaves the nucleus. RN is a temporary copy of DN information that can leave the nucleus. It is referred to as a messenger. mrn RN ribonucleic acid Step 2: Translation ribosomes (cytoplasm) amino acid sequence protein polypeptide chain twists and folds determines cell structure and function determines a characteristic or trait
DN vs. RN Deoxyribose sugar Thymine Ribose sugar Uracil DN (gene): C G T T C G RN ( copy ): G U C U U G C
Messenger RN (mrn) Carries copies of instructions for making proteins Ribosomal RN (rrn) Makes up ribosomes Transfer RN (trn) Carries amino acids to the mrn (at the ribosome)
Transcription Step 1: DN unzips with the help of an enzyme. Step 2: Free RN nucleotides base pair with one side of DN. incoming free RN nucleotides
Step 3: RN strand (now called mrn) detaches from DN and leaves the nucleus. DN zips back up. one gene mrn forming from gene mrn DN re-zips completed mrn, carrying DN information in the matching sequence of nitrogen bases
cell nucleus pores one gene ribosome mrn in cytoplasm, arriving at ribosome
Transcription Review Questions 1. It is said that our DN makes us unique, but how? What does DN actually do? 2. What is an amino acid? 3. What does the m in mrn stand for? 4. Explain the purpose of RN. 5. mrn is a temporary copy of the DN gene. Why is the word copy in quotes?
Sequence the following from smallest to largest: 8 Cell 9 Organ 5 Chromosome 7 Nucleus 3 Nucleotide Organism 4 Gene 2 Nitrogen Base 6 Genome 1 Carbon 10 C Phosphate- Sugar- denine, T, C, or G
Translation (Protein Synthesis step 2) The mrn copy of the gene is used to align amino acids in a specific sequence to make a specific protein. Each amino acid is carried by a specific transfer RN (trn).
Translation ribosome base pairing! This trn (UC) will ONLY carry the amino acid Methionine (Met) This trn (GGG) will ONLY carry the amino acid Proline (Pro)
Translation ribosome growing amino acid chain
Translation ribosome growing amino acid chain
Translation ribosome growing amino acid chain
Translation ribosome growing amino acid chain
Translation ribosome growing amino acid chain
Translation Step 1: Each trn carries a specific amino acid. The trn molecules base pair with the mrn in groups of threes. Codon= group of 3 mrn bases nticodon = group of 3 trn bases that base pair to mrn
Translation Step 1: Each trn carries a specific amino acid. The trn molecules base pair with the mrn in groups of threes. Codon= group of 3 mrn bases nticodon = group of 3 trn bases that base pair to mrn NOTE: there are only 20 amino acids and 64 different trn anticodons each trn can only carry one type of amino acid one type of amino acid can be carried by more than one type of trn
Translation Step 2: The amino acids, held in position at the ribosome, join by dehydration synthesis. The new bonds that connect them are called peptide bonds. Peptide bond
Translation Step 3: mino acids are added one by one to the growing polypeptide chain. This chain will eventually twist and fold to make a protein. The trn molecules are released and will be used again. peptide bond This amino acid chain, once completed, will twist and fold to become a protein. 1) Structural protein 2) Enzyme (control reactions)
Determining amino acid sequence from DN gene. T C T T G C T G T T DN U G U C G C mrn trn mino cid U C U U G C U G U U mrn translation table Methionine sparagine rginine Glutamine T G T C G C template Complimentary strand Start codon UG (Met) Stop codons UG, U, UG