AP Bio - translation

the synthesis of a polypeptide using information from the mRNA

translation

translation occurs at the:

ribosome

in translation, a nucleotide sequence becomes an:

amino acid sequence

• L shaped RNA molecule that has an anticodon at one end and amino acid attachment site at the other

• each carries a specific amino acid and binds to the corresponding codon in mRNA during translation

tRNA

• tRNA has an ___________ region which is complimentary and _________ to mRNA

anticodon, antiparallel

• tRNA carries the _______ ______ that the mRNA codon codes for

amino acid

• the _________ aminoacyl-tRNA synthetase is responsible for attaching amino acids to tRNA

enzyme

what occurs at the ribosome?

translation

small subunit (30s) and large subunit (40s)

prokaryote subunits

small subunit (40s) large subunit (60s)

eukaryote subunits

__ site:

• amino acid

  • holds the next tRNA carrying an amino acid

A site

__ site:

• polypeptide site

  • holds the tRNA carrying the growing polypeptide chain

P site

__ site:

• exit site

E site

how does the tRNA interact with the mRNA?

through its anticodon

what codes for the amino acid?

the mRNA codon

3 stages of translation

1. initiation

2. elongation

3. termination

the small ribosomal subunit binds to the mRNA and a charged tRNA binds to the start codon, AUG, on the mRNA

initiation

the tRNA carries

methionine

the next tRNA comes into the A site

• mRNA is moved through the ribosome and its codons

• each mRNA codon codes for a specific amino acid

elongation

codon recognition: appropriate anticodon of the next tRNA goes to the A-site

1st step of elongation:

peptide bond formation: peptide bonds are formed that transfer the polypeptide to the A-site tRNA

2nd step of elongation

translocation: the tRNA in the A site moves to the P site, the tRNA in the P site goes to the E site

• the A site is open for the next tRNA

3rd step of elongation

a stop codon in the mRNA reaches the A site of the ribosome

• signals for a release factor

termination

the _______ ______

• hydrolyzes the bond that holds the polypeptide to the P site

• polypeptide releases

• all translational units assemble

release factor

chain of amino acids

primary protein

coils and folds due to hydrogen bonds forming

secondary protein

side chain interaction

tertiary protein

2+ polypeptide chains interacting

quaternary protein

______ determine the ________ _____________

genes, primary structure

a protein designed to help polypeptides fold and modify them before they can be fully functional in the cell

chaperone proteins

• information flows from RNA to DNA

• use an enzyme known as reverse transcriptase

retroviruses

a messenger RNA molecule that is being translated by two or more ribosomes

polyribosome

transfer RNA that is covalently bound to an amino acid

aminoacyl tRNA

enzymes that catalyze the addition of a particular amino acid to its corresponding tRNA molecule

aminoacyl tRNA synthetases

• allows one tRNA to read more than one codon

• 40 tRNAs can translate all 61 codons

wobble pairing

class of proteins that assist ribosomes in binding to a messenger RNA molecule to begin translation

initiation factors

• more initiation factors needed

• ribosome first associates with 5’ cap of mRNA

• initiator tRNA carries a normal methionine

initiation in eukaryotes

• mRNA binds to small ribosomal subunit

• the initiator tRNA bearing f-Met binds to the start codon

• the large ribosomal subunit binds

initiation in bacteria

movement of a ribosome down a messenger RNA

translocation

any class of proteins that assist ribosomes in the synthesis of the growing peptide chain

elongation factor

• protein folding

• chemical modifications

post-translational modification