Protein synthesis Flashcards
5’ cap structure [2 mark]
- 7-methylguanosine residue linked to a triphosphate at 5’ end.
- next 2 nucleotides after cap have methylated 2’-OH on ribose halves.
How many adenylic residues are added at the 3’ end? [1 mark]
100 to 250
How many amino acids can be made? [1 mark]
20
How many possible codons are there? [1 mark]
64
How many amino acids can ribosomes add per second? [1 mark]
20
What are the ribosomes for prokaryotic and eukaryotic cells? [2 marks]
Prokaryotic: 70S
Eukaryotic: 80S
What are the large and small ribosomal subunits for prokaryotic and eukaryotic cells? [2 marks]
Prokaryotic: 50S & 30S
Eukaryotic: 60S & 40S
What are the large ribosomal subunit components of prokaryotic and eukaryotic cells? [2 marks]
Prokaryotic: 23S & 5S RNA, 31 proteins
Eukaryotic: 28, 5.8S & 5S RNA, 49 proteins
What are the small subunit components of prokaryotic and eukaryotic cells? [2 mark]
Prokaryotic: 16S, 21 proteins
Eukaryotic: 18S, 33 proteins
What is initiation of protein synthesis? [1 mark]
Assembly of the ribosome on mRNA with met-tRNAi
What does eIF2 do? [1 mark]
Binds to met-tRNAi and GTP on the P site.
What does eIF1, eIF1A and eIF3 do? [1 mark]
Binds to the 40S subunit to form the 43S preinitiation complex
What forms the 48S preinitiation complex? [2 marks]
- 43S preinitiation complex
- mRNA
What does eIF5 do? [2 marks]
- Hydrolyses GTP
- Causes eIF2 and eIF3 to be released
What is the start codon in eukaryotes? [1 mark]
AUG
What does eIF1 do? [1 mark]
Allows the charged tRNA to enter the A site
What is elongation? [1 mark]
Adding 1 amino acid at a time to form the polypeptide
Which enzyme allows tRNA to be charged and hydrolysis EF1 and GTP? [1 mark]
Aminoacyl-tRNA synthase (binds to A site)
Which enzyme translocates the amino acid to the polypeptide? [1 mark]
Peptidyltransferase
Which enzyme translocates the 80S ribosome and hydrolyses EF2 and GTP? [1 mark]
Translocase
What does the release factor do? [1 mark]
Recognises and binds to the stop codon
What causes polysomes? [1 mark]
Binding of many ribosomes to an individual mRNA molecule
