L16 translation 1

What are proteins composed of

Amino acids

How many amino acids are used to make proteins

Twenty

What type of bond links amino acids

Peptide bond

What groups form a peptide bond

Carboxyl and amino groups

How many codons encode amino acids

Sixty one

How many stop codons exist

Three

What is meant by degeneracy of the genetic code

Multiple codons encode the same amino acid

Which amino acids have only one codon

Methionine and tryptophan

What codon is used for initiation

AUG

What does mRNA do

Encodes protein sequence

What is the role of rRNA

Forms part of ribosome and catalyses translation

What is the role of tRNA

Brings amino acids and matches codons

What is the structure of tRNA

Cloverleaf

What sequence is added to tRNA after transcription

CCA tail

What unusual bases are found in tRNA

Pseudouridine and dihydrouridine

What is aminoacylation

Charging of tRNA with amino acid

What enzyme carries out aminoacylation

Aminoacyl tRNA synthetase

What cofactor is required for aminoacylation

ATP

What is a charged tRNA

Aminoacyl tRNA

Where is the amino acid attached on tRNA

Three prime or two prime OH of terminal adenine

How many aminoacyl tRNA synthetases exist

At least twenty

What ensures specificity in aminoacylation

Editing by synthetases

What type of base pairing occurs between codon and anticodon

Watson Crick pairing

What is wobble pairing

Flexible pairing at third codon position

What does wobble contribute to

Degeneracy of genetic code

What is usually the first amino acid in proteins

Methionine

What special tRNA is used for initiation in prokaryotes

tRNAfmet

What special tRNA is used for initiation in eukaryotes

tRNAimet

What is used for elongation methionine

tRNAmmet

What are the two ribosomal subunits

Large and small

What molecule makes up most of the ribosome

rRNA

What is the rate limiting step of translation

Initiation

What sequence helps ribosome bind mRNA in prokaryotes

Shine Dalgarno sequence

Where does Shine Dalgarno bind

Sixteen S rRNA

What do IF1 and IF3 do

Guide initiator tRNA and prevent large subunit binding

How many sites are in the ribosome

Three

What are the ribosome sites

A P and E

What is the A site

Aminoacyl site

What is the P site

Peptidyl site

What is the E site

Exit site

What does EFTu do

Brings aminoacyl tRNA to ribosome

What happens to EFTu during elongation

Hydrolyses GTP and leaves

What catalyses peptide bond formation

Peptidyl transferase centre

Is peptidyl transferase a protein enzyme

No

What type of molecule catalyses peptide bond formation

Ribozyme

What ribosomal subunit contains peptidyl transferase

Fifty S subunit

What are ribozymes

Catalytic RNA molecules

What cellular processes involve ribozymes

RNA splicing and intron removal

What is translocation

Movement of ribosome along mRNA

What direction does ribosome move

Three prime direction

What factor is required for translocation

EFG

What energy source is required for translocation

GTP

What happens to peptidyl tRNA during translocation

Moves from A site to P site

What happens to uncharged tRNA during translocation

Moves from P site to E site

What happens to EFG after translocation

Released and reused

What is structural similarity between EFG and EFTu

EFG mimics EFTu tRNA complex

Where does EFG bind

A site

What drives conformational changes during translocation

GTP hydrolysis

How far does ribosome move each step

Three bases

What are the steps of elongation

tRNA binding peptide bond formation and translocation

What happens to tRNA in E site during elongation

It is displaced

How long can polypeptide chains become

Over one thousand amino acids

What happens at stop codons

Release factors bind

What does RF1 recognise

UAA and UAG

What does RF2 recognise

UAA and UGA

Why does no tRNA bind stop codons

No corresponding anticodon exists

What is ribosome recycling factor

Protein that helps disassemble ribosome

What promotes ribosome disassembly

RRF and EFG GTP

What does IF3 do during recycling

Stabilises small subunit