Translation - Ribosomes and overview of process Flashcards
What are the two steps of translation?
Capturing complementary tRNA molecules and holding them in position (to allow the tRNA anticodons to base-pair with mRNA codons)
Covalently linking the amino acids that tRNAs carry so as to form a protein chain
What is the protein manufacturing machine?
The ribosome
Where are ribosomal subunits made in eukaryotes?
Made in nucleus
What does the small ribosomal subunit do?
Matches tRNAs to codons of mRNA
What does the large ribosomal subunit do?
It catalyses formation of peptide bonds that link amino acids together into a polypeptide chain
Where and why do the 2 ribosomal subunits come together?
They come together on an mRNA molecule - near 5’ end
This allows them to begin synthesis of protein
How does the ribosome work?
2
It moves along mRNA
As it does so it translates the nucleotide sequence into an amino acid sequence, one codon at a time
How does the ribosome work with tRNA
The ribosome uses tRNAs as adaptors to add each amino acid in the correct sequence
What happens to the ribosome when protein synthesis is completed?
The 2 subunits of the ribosome separate
How many amino acids are added per second to a polypeptide chain by ribosomes in eukaryotic cells?
Ribosomes add 2 amino acids to a polypeptide chain per second in eukaryotes
How much faster are prokaryotic ribosomes than eukaryotic ribosomes?
Prokaryotic ribosomes are ten times faster than eukaryotic
What are the three binding sites for tRNA?
P site
A site
E site
What is the P site of a ribosome?
2
The peptidyl-tRNA site
It holds the tRNA that is carrying the growing polypeptide chain
What is the A site of a ribosome?
2
The aminoacyl-tRNA site
It holds the tRNA that is carrying the next amino acid to be added to the chain
What is the E site of a ribosome?
2
The exit site
This is where discharged tRNAs leave the ribosome