7.3 Translation Flashcards
What are ribosomes made of?
Proteins and ribosomal RNA
Why are ribosomes made of proteins?
For stability
Why are ribosomes made of ribosomal RNA?
For catalytic activity
What do ribosomes consist of?
A large and small subunit
What does the small ribosome subunit consist of?
An mRNA binding site
What does the large ribosomal subunit consist of?
Three tRNA binding sites
What are the three binding sites on the large subunit called?
Aminoacyl (A) site
Peptidyl (P) site
Exit (E) site
Where can ribosomes be found?
Freely floating in the cytosol or bound to the rough ER
What are the two sizes of ribosomes?
Prokaryotes = 70S
Eukaryotes = 80S
What is the structure of the tRNA molecule?
A cloverleaf structure with four regions
What are the four regions of the tRNA molecules?
The acceptor stem
The anticodon
The T arm
The D arm
What does the acceptor stem carries?
An amino acid
What does the anticodon associate with?
The mRNA codon
How does the anticodon associated with the mRNA codon?
Via complementary base pairing
What does the T arm associate with?
The ribosome
How does the T arm associate with the ribosome?
Via the E, P and A binding sites
What does the D arm associate with?
The tRNA activating enzyme
What is the tRNA activating enzyme responsible for?
Adding the amino acid to the acceptor stem
What does each tRNA molecule bind with?
A specific amino acid
Where does the tRNA molecule bind with specific amino acids?
In the cytoplasm
What catalyses the binding between tRNA molecule and amino acid?
A tRNA activating enzyme
What is each amino acid recognised by?
A specific enzyme
Why may the enzyme recognise multiple tRNA molecules?
Due to degeneracy
What is the two step process of an amino acid binding to the tRNA acceptor stem?
The enzyme binds ATP to the amino acid to form an amino acid AMP complex
The amino acid is then coupled to tRNA and the AMP is released and the tRNA molecule is charged
What is the function of the ATP in tRNA activation?
To create a high energy bond that is transferred to the tRNA molecule
What does the stored energy do in tRNA activation?
Provides the majority of the energy required for peptide bond formation during translation
What does the initiation stage of involve?
The assembly of the three components that carry out the process (mRNA, tRNA, ribosome)
In initiation, where does the small ribosomal subunit bind to?
The 5’- end of the mRNA
In initiation, up until what point does the small ribosomal subunit move along the mRNA?
Until it reaches the start codon
In initiation, what happens when the small ribosomal unit reaches the start codon?
The appropriated tRNA molecule bind to the codon via its anticodon
How does te tRNA molecule bind to the codon via its anticodon?
Complementary base pairing
In initiation, where does the large ribosomal subunit aligns itself to the tRNA molecule?
At the P site
In initiation, what does the large subunit do once it is at the P site?
Forms a complex with the small subunit
In elongation, what does the second tRNA molecule do?
Pairs with the next codon
In elongation, where does the second tRNA molecule pair with the next codon?
At the A site
In Elongation, what happens to the amino acid in the P site?
It is covalently attached to the amino acid in the A site
In elongation, via what type of bond and reaction is the amino acid in the P site attached to the amino acid in the A site?
A peptide bond and condensation reaction
In elongation, after the tRNA in the p site attaches to the A site, what happens to the tRNA in the P site?
It is now deacylated