AP Bio Chapter 17 Part 5 Flashcards
Where does polypeptide leave ribosome
Exit channel
What does a codon code for
Amino acid
No chemical effect
What’s tRNA responsible for
Transfer RNA
Responsible for bringing amino acids to the ribosome
How are amino acids added to the tRNA molecules
The action of “amino-acyl tRNA synthase” enzymes
When is a tRNA “charged”
When it has an amino acid attached to it
Why is the genetic code special
Universal all domains
Triplet code
mRNA is read in units of 3 bases (codons)
How many possible codons are there for possible amino acids
64 possible codons for 20 possible amino acids
What is bad about the code
Redundant and ambiguous
What are the punctuations of the code
Start and stops
What could a codon’s bases not be less than
3
What happens in initiation of translation
The mRNA attaches to the small ribosomal subunit
Methionine is brought to the start codon (AUG) by the methionine tRNA
The ribosome assembles so that the start codon (AUG) in in the p site
What is the assembled ribosomes on the mRNA called
Translation initiation complex
What does the anti codon loop in tRNA do
Mediates tRNA binding at the ribosomes
What is the first step in elongation in translation
The next codon determines the next amino acid to be brought to the ribosome and the incoming charged tRNA enters at the A site
What is the second step of elongation in translation
The growing polypeptide is transferred to the new tRNA molecule. A peptide bond is formed
What is the 3rd step in elongation of translation
The ribosomes shifts (translocates) the tRNA with the polypeptide is now in the p site, the uncharged polypeptide us now in the e site
What is the last step of elongation in translation
The next codon is now available in the A site for the next incoming charged tRNA
What happens at termination of translation
When a stop codon (NAG, UAA, or UGA) is encountered a release factor binds to the A site
The polypeptide is released
The ribosome disassembles
What is special about prokaryotes because they don’t have a nucleus
Transcription and translation can be coupled
What’s the concept of polyribosomes in prokaryotes
Simultaneous translation of a transcript, even while the transcript is still being made
How is eukaryotic transcription and translation different from prokaryotic
Eukaryotes do not couple transcription and translation, they also do not have polyribosomes
What do eukaryotes also need to target
Different polypeptides to different areas of the cell
What’s a signal peptide (eukaryotes)
A small signal peptide sequence on polypeptides that need to be made at the endoplasmic reticulum, recruits an SRP protein, which modulates “docking” of the ribosome to the rough ER
