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Genes and early embryology > Protein synthesis > Flashcards

Protein synthesis Flashcards

1
Q

What is Riacin and what does it do

A

N-glycosidase

-inactivates large eukaryotic ribosome

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2
Q

What are the functions of the ribosome

A
  • binds mRNA so codons can be read
  • BInding sites for tRNA
  • mediate the interaction of non-ribosomal protein factors promoting: polypeptide chain initiation, polypeptide chain elongation and polypeptide chain termination
  • catalyse peptide bond formation
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3
Q

What does the movement of ribosome allow

A

Translation of sequential codons

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4
Q

Where are prokaryotic ribosomal proteins found

A

Located on subunit back and sides

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5
Q

IN prokaryotes, what are the names of the tRNA binding sites

A
  • A site
  • P site
  • E site
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6
Q

What is the A site on a prokaryotic ribosome

A

Accommodates incoming amino-acyl-tRnA

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7
Q

Wat is the P site on prokaryotic ribosome

A

Accommodates the tRNA attached to growing peptide chain

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8
Q

What is the E site on prokaryotic ribosome

A

Accommodates the tRNA without amino acid, that is leaving

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9
Q

How do tRNA’s bind to eukaryotic ribosomes

A

all 3 tRNA have anticodons bound to 30s subunit and the rest of the tRNA bound to 50s subunit

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10
Q

What do the tRNA on the A site and P site interact with the mRNA via

A

Base-pairing

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11
Q

What is elongation in translation

A
  • links growing polypeptide to incoming tRNA amino acid
  • Growing polypeptide transferred from peptide-tRNA in the p site to the incoming amino acid tRNA in A site
  • new peptidyl-tRNA is transferred from A to P site
  • Uncharged tRNA moves to E site
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12
Q

what is polycistronic

A

When prokaryotic mRNA has more than one coding region and each coding region has its own initiation and termination codons

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13
Q

What is monocistronic

A

mRNA has just one coding region

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14
Q

What is polysome

A

multiple ribosomes can translate a message because of length of mRNA

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15
Q

What is initiation and what happens in it

A

involves assembly of translation system components

  • mRNa
  • 2 ribosomal subunits
  • amino acyl-tRNA specified by the 1st codon
  • GTP
  • Initiation factors
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16
Q

What do ribosomes recognize the start codon via

A

Shine-Delgarno sequence (not in eukaryotes)

17
Q

What are the stages of initiation

A
  • ribosomes recognize start codon (only in prokaryotes)
  • initiation and binding of tRNA in P site
  • HYdrolysis of GTP and initiation factors are released
  • allows large subunits to bind
18
Q

What happens in elongation

A
  • Involves addition of amino acid to carboxyl end of growing chain
  • Delivery of the next amino-acyl tRNA by elongation factors which requires GTP hydrolysis
  • Ribosome them advances 3 nucleotides to mRNA 3’ end (translocation)
19
Q

What happens in termination

A
  • termination codons recognized by release factors
  • Allow GTP to hydrolase and release of protein because RF binding causes hydrolysis pf bond linking peptide to tRnA on p-site and so protein is released
20
Q

What do antibiotics do

A

Block translation

21
Q

What does a low level of streptomycin mean

A

Ribosome misreads mRNA

22
Q

What does a high level of streptomycin mean

A

Prevents chain initiation (causes cell death)

23
Q

What does chloramphenicol do

A

Binds near A site and stops peptide formation. HOWever its toxic because it affects mitochondrial translation

24
Q

What does tetracycline do

A
  • Bind to small subunit or prokaryotic ribosomes and prevents entry of amino acyl-tRNA into A site
  • Stops synthesis and is an energy drain
  • However allow elongation factors to bind
25
Q

What folds proteins

A

Chaperones

26
Q

What is phsphorylation reversedby

A

PHosphatases

27
Q

what is phosphorylation catalysed by

A

kinases

28
Q

How are proteins directed to their ultimate destinations

A

Small ubiquitin related modifier addition can signal cellular localisation

29
Q

HOW are many transmembrane and secretory proteins translocated through membranes via

A

Secretory pathway through ER

  • as N terminal signal sequences emerge from ribosome, associate with signal recognition particle
  • Docks with ER receptor
  • PRotein synthesis takes place and pushes the protein into the ER
  • Post translational modification occurs

Genes and early embryology (12 decks)

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