Making Proteins:Translation

Lecture #25Honors Biology

Ms. Day

REVIEW…Translation

mRNA polypeptide (protein)

Type of RNA Function Job Picture

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

tRNAA cell translates mRNA message into

protein with help from transfer RNA (tRNA)Each carries a specific amino acid“t” shapeCarries amino acidsMatches codons to anticodons

RibosomesHelp bind tRNA anticodons

with mRNA codons during translation

Anticodon (tRNA) = 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 acids3 letter mRNA “word” = 1 amino acid

There are 4 different RNA “letters” that can be used

A, U, C, and G

THE GENETIC

CODE

RibosomesThere are 2 ribosomal subunits

Constructed of proteins and ribosomal RNA or rRNA

Building a PolypeptideTranslation can be divided into 3 phasesInitiationElongationTermination

Initiation of Translationinitiation stage brings

togethermRNAtRNA bearing 1st amino acid

(“start”) called MET2 subunits of a ribosome come

together

Large ribosomal subunit

Initiator tRNA

mRNA

mRNA binding site Smallribosomalsubunit

Translation initiation complex

GDPGTP

Start codon

Met MetU A C

A U G

3

5

5

3

35 35

Elongation Amino acids are added one by one

to the preceding amino acidPeptide bonds are formed

Amino acid

Termination of TranslationWhen the ribosome reaches a stop codon on the

mRNAThere are 3 stop codons

UAA, UAG, and UGARelease factor (protein) binds to stop codon (NOT tRNA)

polypeptide released

Termination of TranslationRelease factor Free

polypeptide

Stop codon(UAG, UAA, or UGA)

5

3 35

35

Figure 17.13

TRANSCRIPTION

TRANSLATION

DNA

mRNA

Ribosome

Polypeptide

Polypeptide

Aminoacids

tRNA with amino acid attachedRibosome

tRNAAnticodon

mRNA

Trp

Phe Gly

A G C

A A A

C C G

U G G U U U G G C

Codons5 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

1 2

3 4

Translation (Protein Synthesis) Animation

http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter15/animations.html#

https://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter3/animation__how_translation_works.html

http://www.biostudio.com/demo_freeman_protein_synthesis.htm