tRNA Structure and Function

What is the approximate length of a transfer RNA (tRNA) molecule?

50 nucleotides
120 nucleotides
100 nucleotides
80 nucleotides (correct)

What is the function of the short single-stranded region at the 3ʹ end of a tRNA molecule?

Recognizing codons in mRNA
Attaching amino acids to tRNA (correct)
Binding to ribosomes
Pairing with other tRNA molecules

How many different types of synthetase enzymes are typically present in most cells?

10
40
20 (correct)
60

What is the reason why there are not 64 different types of tRNA?

Some tRNA can recognize more than one codon (A) Signup and view all the answers

What type of base pairing occurs in the wobble position of the anticodon?

Non-canonical base pairing (B) Signup and view all the answers

What is the function of aminoacyl-tRNA synthetases?

To couple each amino acid to its appropriate tRNA molecule (A) Signup and view all the answers

What is the primary function of the A site and the P site in a ribosome?

To form base pairs with adjacent codons on the mRNA molecule (B) Signup and view all the answers

What is the consequence of tRNA binding to the ribosomal A site?

The P site and the A site contain adjacent bound tRNAs (B) Signup and view all the answers

What is the significance of the 'wobble' in the anticodon of the tRNA molecule?

It allows for specific binding of tRNA to the mRNA molecule, despite variations in the codon (A) Signup and view all the answers

What is the outcome of protein synthesis initiation?

Each new amino acid is added to the elongating chain in a cycle of reactions (C) Signup and view all the answers

What is the role of the E site in a ribosome?

It is not mentioned in the text as a specific site (D) Signup and view all the answers

What is the outcome of the tRNA binding to the ribosomal A site in step 1 of protein synthesis?

The P site and the A site contain adjacent bound tRNAs (A) Signup and view all the answers

What is the role of initiation factors in protein synthesis?

They recognize the initiator tRNA–methionine complex (D) Signup and view all the answers

What would be the consequence of an error of one nucleotide in the starting site of protein synthesis?

The reading frame would be shifted, resulting in a nonfunctional protein (A) Signup and view all the answers

What is the function of the initiator tRNA in protein synthesis?

It carries the amino acid methionine and starts translation (B) Signup and view all the answers

What is the role of the sequence AUG in protein synthesis?

It signals the start of protein synthesis (B) Signup and view all the answers

What is unique about the initiator tRNA compared to other tRNAs carrying methionine?

It has a different nucleotide sequence (C) Signup and view all the answers

Where does the initiator tRNA–methionine complex get loaded in eukaryotes?

The small ribosomal subunit (D) Signup and view all the answers

What is the advantage of multiple initiations of protein synthesis in eukaryotes?

It enables the cell to produce more protein molecules in a given time (B) Signup and view all the answers

What is the significance of the 5ʹ and 3ʹ ends of mRNA in eukaryotes?

They interact, allowing for rapid reinitiation of translation (B) Signup and view all the answers

Why are certain antibiotics effective against bacteria but not eukaryotes?

Because they exploit structural and functional differences between bacterial and eukaryotic ribosomes (C) Signup and view all the answers

What is the implication of the multiple steps from DNA to protein?

It provides multiple opportunities for regulation of gene expression (A) Signup and view all the answers

What is the advantage of using inhibitors of prokaryotic protein synthesis as antibiotics?

They can be taken in high dosages without undue toxicity to humans (D) Signup and view all the answers

What is the function of release factors in protein synthesis?

To bind to a ribosome with a stop codon to catalyze the addition of a water molecule (B) Signup and view all the answers

What happens to the growing polypeptide chain after the addition of a water molecule?

It is released into the cytoplasm (C) Signup and view all the answers

What is the purpose of multiple initiations on an mRNA molecule?

To increase the rate of protein synthesis (C) Signup and view all the answers

What is the term for a large cytoplasmic assembly made up of several ribosomes spaced along a single mRNA molecule?

Polyribosome (A) Signup and view all the answers

What happens to the ribosome after the release of the completed protein chain?

It is recycled for another round of protein synthesis (D) Signup and view all the answers

What is the typical time range for the synthesis of a protein molecule?

20 seconds to several minutes (B) Signup and view all the answers