BIOL 112 Lecture Notes - Lecture 21: Aminoacyl-Trna, Ribosome-Binding Site, Start Codon

Facts about ribosomes

Indicate whether each of the following statements aboutribosomes is true or false.

1. Ribosomes are composed of tRNA and protein. TrueFalse
2. During translation in eukaryotes, some ribosomes remain free inthe cytoplasm while others attach to protein channels embedded inthe RER. TrueFalse
3. During initiation of translation, the small ribosomal subunitjoins to the mRNA and initiator rRNA, followed by the largeribosomal subunit. TrueFalse
4. When a ribosome first assembles on the mRNA, the initiator tRNAoccupies the A site while the P and E sites are empty.TrueFalse
5. During translation, a charged tRNA first binds to the ribosomeif its anticodon matches the codon in the E site. TrueFalse
6. A peptide bond forms between the amino acid attached to a tRNAin the A site and the growing polypeptide attached to a tRNA in theP site. TrueFalse
7. Uncharged tRNA molecules in the E site are ejected from theribosome. TrueFalse
8. No more than 2 tRNA molecules are bound to a ribosome at anygiven time. TrueFalse
9. During translocation of the ribosome, tRNA molecules move fromthe P site, to the A site, to the E site, and are then ejected fromthe ribosome. TrueFalse
10. During translation, an amino acid attached to a tRNA in the Asite is transferred to a growing polypeptide attached to a tRNA inthe P site. TrueFalse

Facts about ribosomes

Indicate whether each of the following statements aboutribosomes is true or false.

1. Ribosomes are composed of tRNA and protein. TrueFalse
2. During translation in eukaryotes, some ribosomes remain free inthe cytoplasm while others attach to protein channels embedded inthe RER. TrueFalse
3. During initiation of translation, the small ribosomal subunitjoins to the mRNA and initiator rRNA, followed by the largeribosomal subunit. TrueFalse
4. When a ribosome first assembles on the mRNA, the initiator tRNAoccupies the A site while the P and E sites are empty.TrueFalse
5. During translation, a charged tRNA first binds to the ribosomeif its anticodon matches the codon in the E site. TrueFalse
6. A peptide bond forms between the amino acid attached to a tRNAin the A site and the growing polypeptide attached to a tRNA in theP site. TrueFalse
7. Uncharged tRNA molecules in the E site are ejected from theribosome. TrueFalse
8. No more than 2 tRNA molecules are bound to a ribosome at anygiven time. TrueFalse
9. During translocation of the ribosome, tRNA molecules move fromthe P site, to the A site, to the E site, and are then ejected fromthe ribosome. TrueFalse
10. During translation, an amino acid attached to a tRNA in the Asite is transferred to a growing polypeptide attached to a tRNA inthe P site. TrueFalse

22. There are 20 amino acids and 64 possible codons. Which of the following is closer to the actual number of different tRNA molecules in a cell?

A. 4

B. 16

C. 20

D. 61

E. 64

23. There are 20 amino acids and 64 possible codons. How many different eukaryotic aminoacyltRNA synthetases are there? A. 1

B. 16

C. 20

D. 61

E. 64

24. Which way are the amino acid and tRNA attached in a charged tRNA?

A. Amino acid-5'tRNA3'-AMP B

. Amino acid-AMP-3'tRNA

C. AMP-amino acid-3'tRNA

D. Amino acid-3'tRNA5'-AMP

E. Amino acid-AMP-5'tRNA

25. The anticodon that recognizes the initiation codon in translation is

A. 5' AUG 3'

B. 3' AUG 5'

C. 5' ACU 3'

D. 5' UAC 3'

E. 3' UAC 5'

26. The first amino acid incorporated into a growing polypeptide

A. In bacteria is methionine and it is also methionine in eukaryotes

B. In bacteria is tryptophan, while it is methionine in eukaryotes

C. In bacteria is N-formyl methionine, while it is methionine in eukaryotes

D. In bacteria is N-formyl methionine and it is also N-formyl methionine in eukaryotes

E. In bacteria is methionine, while it is N-formyl methionine in eukaryotes

27. In E. coli the IF3 forces tRNAf Met to bind with

A. The A site of the ribosome

B. The P site of the ribosome

C. The E site of the ribosome

D. IF1

E. IF2