Lecture 12: Translation Flashcards
What is the triplet codon hypothesis
suggests that three consecutive nucleotides (a codon) in mRNA code for a single amino acid during protein synthesis.
(One protein can have many codons)
What codon specifies start
AUG (methionine)
How many codons specify stop
3
UAA, UAG, and UGA
How long is tRNA molecule
70-80 nucleotides in length
What is tRNA
A single strand of RNA, an adaptor molecule
how trna acts as an adaptor molecule
linking amino acids to the mRNA code. It carries a specific amino acid at one end (the amino acid acceptor end) and has an anticodon on the other end that binds to a corresponding codon on the mRNA.
How many types of aminoacly tRNA synthase enzymes are there?
20, one for each amino acid
Explain how tRAN is “Charged”
tRNA and amino acid enter active site of enzyme
ATP syntase catalyzes covalent bonding between the two
Aminoacyl (charged) tRNA is released
What is translation?
Translation is the synthesis of
proteins by ribosomes using
mRNA as a set of instructions
What is the order of sites in the ribosome
EPA
What is the P site
The P site is peptidyl-tRNA binding site
What makes the rER rough?
Ribosomes attatched to its outer surface. sER lacks ribosomes, giving it a smooth apperance
What do ribosomes bound to the rER do?
They synthesize proteins that are used within the plasma membrane or are exocytosed from the cell
What do ribosomes free in the cytosol do?
synthesize proteins that are released into the cytosol and used within the cell
What are the 3 stages of translation
Initiation, Elongation, Termination
What is the first step in initiation
A specific initiation tRNA (carrying methionine) binds to the small
ribosomal subunit.
What happens when the ribosome reaches a stop codon?
a protein called release
factor enters the A site.
The release factor breaks the bond between the P site tRNA (using
water) and the final amino acid. This causes the polypeptide chain
to detach from its tRNA and the newly made polypeptide is
released.
