Unit 6 - topic 4 Flashcards
translation
synthesis of a polypeptide using information from the mRNA
a nucleotide sequence becomes
an amino acid sequence
tRNA is a key player in
translating mRNA to an amino acid sequence
transfer RNA
has an anticodon region which is complementary and antiparallel to mRNA
tRNA carries
the amino acid that the mRNA codon codes for
enzyme aminoacyl-tRNA synthetase is responsible for
attaching amino acids to tRNA
when tRNA carries an amino acid it is
“charged”
translation occurs at the
ribosome
ribosomes have two subunits
small and large
prokaryote subunit
small subunit (30s) large subunit (40s)
eukaryote subunit
small subunit (40s) large subunit (60s)
large subunit has three sites
A, P, and E
A site
amino acid site
holds the next tRNA carrying an amino acid
P site
polypeptide site
holds the tRNA carrying the growing polypeptide chain
E site
exit site
initiation
- small ribosomal subunit binds to the mRNA and a charged tRNA binds to start codon AUG on mRNA
- tRNA carries methionine
- large subunit binds
elongation
- next tRNA comes into A site
- mRNA is moved through ribosome and its codons are read
- each mRNA codon codes for a specific amino acid
- codon charts are used to determine amino acid
common ancestry
idea that all organisms use the same genetic code
elongation steps order
codon recognition
peptide bond formation
translocation
codon recognition
appropriate anticodon of next tRNA goes to A-site
peptide bond formation
peptide bonds are formed that transfer the polypeptide to A site tRNA
translocation
tRNA in A site moves to P site, tRNA in P site goes to E site. A site is open for next tRNA
termination
- termination occurs when a stop codon in the mRNA reaches the A site of the ribosome
- stop codons do not code for amino acids
- stop codon signals for a release factor
release factor
- hydrolyzes bond that holds the polypeptide to P site
- polypeptide releases
- all translational units disassemble
primary
chain of amino acids
secondary
coils and folds due to hydrogen bonds forming
tertiary
side chain interaction
quaternary
2+ polypeptide chains interacting
protein folding
as translation takes place, growing polypeptide chain begins to coil and fold
genes determine
primary structure
primary structure determines
final shape
some polypeptides require
chaperone proteins to fold correctly and some require modification before it can be functional in cell
retroviruses
retroviruses, like HIV, are an exception to the standard flow of genetic information
information flows from
RNA to DNA
uses an enzyme known as reverse transcriptase
reverse transcriptase
couples viral RNA to DNA
DNA then becomes part of RNA
