Making Proteins: Translation Lecture #25 Honors Biology Ms. Day

REVIEW… Translation mRNA  polypeptide (protein)

Type of RNAFunction JobPicture mRNA (messenger RNA) Brings message from DNA (DNA instructions) to ribosome to make protein tRNA (transfer RNA) Transfers/moves amino acids to ribosomes rRNA (ribosomal RNA) Makes up ribosomes along with proteins

tRNA A cell translates mRNA message into protein with help from transfer RNA (tRNA) Each carries a specific amino acid “t” shape Carries amino acids Matches codons to anticodons

Ribosomes Help bind tRNA anticodons with mRNA codons during translation An t icodon ( t RNA) = codon (mRNA)

tRNA (with anticodons) mRNA (with codons) AMINO ACIDS

REVIEW…The Genetic Code It’s a table used that TRANSLATES RNA nucleotides called CODONS (or mRNA “letters”) into one of the 20 amino acids 3 letter mRNA “word” = 1 amino acid There are 4 different RNA “letters” that can be used A, U, C, and G

THE GENETIC CODE

Ribosomes There are 2 ribosomal subunits Constructed of proteins and ribosomal RNA or rRNA

Building a Polypeptide Translation can be divided into 3 phases Initiation Elongation Termination

Initiation of Translation initiation stage brings together mRNA tRNA bearing 1 st amino acid (“start”) called MET 2 subunits of a ribosome come together

Large ribosomal subunit Initiator tRNA mRNA mRNA binding site Small ribosomal subunit Translation initiation complex GDP GTP Start codon Met U A C A U G Figure 17.17

Elongation Amino acids are added one by one to the preceding amino acid Peptide bonds are formed Amino acid

Termination of Translation When the ribosome reaches a stop codon on the mRNA There are 3 stop codons UAA, UAG, and UGA Release factor (protein) binds to stop codon (NOT tRNA)  polypeptide released

Termination of Translation Release factor Free polypeptide Stop codon (UAG, UAA, or UGA)

Figure TRANSCRIPTION TRANSLATION DNA mRNA Ribosome Polypeptide Amino acids tRNA with amino acid attached Ribosome tRNA Anticodon mRNA Trp Phe Gly A G C A AA C C G U G GU U U GG C Codons 5 3 “EMPTY” tRNA

Polypeptide  3D Protein Primary Structure Amino acids is a row (LINEAR) Secondary Structure Amino Acids BEND and FOLD towards each other Tertiary Structure Amino acids BIND to each other 3D shape made Quartnary structure (only some) 2 or more polypeptides BIND to each other

Translation (Protein Synthesis) Animation online.com/objects/index_tj.asp?objID=AP online.com/objects/index_tj.asp?objID=AP hill.com/sites/ /student_view0/cha pter15/animations.html# hill.com/sites/ /student_view0/cha pter15/animations.html# hill.com/sites/ /student_view0/cha pter3/animation__how_translation_works.htm l hill.com/sites/ /student_view0/cha pter3/animation__how_translation_works.htm l tein_synthesis.htm tein_synthesis.htm