lecture 17 - translation Flashcards
How are amino acids coded for?
Triplets of base pairs called codons.
How many codons are there?
4^3 = 64 codons
How many codons specify an amino acid?
61
How many amino acids code for STOP?
3
What codon specifies start?
AUG
Why are there only 20 amino acids when there are many more codons?
Several codons code for the same amino acid. e.g. CAT and CAC both code for His (H)
What is tRNA?
transport RNA - an adapter that carries specific amino acids to the template strand (mRNA) and allows them to fit together.
What is the structure of tRNA
single strand, 70-80 nucleotides long that folds up, giving it an Amino acid attachment site at one end and an anticodon at the other end.
What does the anticodon of tRNA interact with?
Codon sequence of mRNA
What is the process of charging tRNA?
An enzyme (aminoacyl-tRNA synthetase) recognises both a specific specific amino acid and the appropriate tRNA molecule, joining them together at the tRNA attachment site. ATP is used to bind them covalently at the active site of the enzyme.
How many different aminoacyl tRNA synthesise enzymes are there?
20 - one for each different amino acid.
What is translation?
The synthesis of proteins by ribosomes using mRNA as a ‘set of instructions’.
What do ribosomes contain?
Ribosomal RNA (rRNA) and proteins.
Where are ribosomes found?
rER and free in cytosol of cell.
What are the components of a ribosome? (4)
Large subunit, small subunit, E, P, A sites, exit tunnel.