6.6.5 Elongation Continued and Termination Flashcards Preview

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Flashcards in 6.6.5 Elongation Continued and Termination Deck (8)
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1
Q

note

A
  • During the elongation stage of translation a new polypeptide is synthesized by linking amino acids with peptide bonds.
    • Review: During elongation, incoming tRNAs move from the A site to the P site. The tRNA in the P site moves to the E site and leaves the ribosome. The step requires an energy expenditure in the form of GTP. During elongation the mRNA moves through the ribosome 5’ end first
2
Q

Termination

A
  • of translation occurs when a stop codon reaches the A site of the ribosome. A protein release factor binds
    to the stop codon and hydrolyzes the bond between the tRNA in the P site and the last amino acid of the polypeptide chain. The polypeptide is released.
3
Q

Peptide bonds

A
  • link amino acids in a polypeptide chain. The
    peptide bonds are formed by dehydration reactions and link the carboxyl group of one amino acid to the amino group of the next. Water is a by-product of the dehydration reaction.
  • Elongation continues until a stop codon reaches the A site of the ribosome. 1. A protein release factor binds to the stop codon, causing the addition of a water molecule instead of an amino acid to the polypeptide chain. 2. The release factor hydrolyzes the bond between the tRNA in the P site and the last amino acid of the polypeptide chain. The polypeptide is released from the ribosome and floats off into the sunset. 3. The complex of mRNA, tRNA, and ribosomal subunits dissociate and the molecules can be recyled by the cell to construct more proteins.
4
Q

Match the following terms with the appropriate descriptions and choose the correct order of answers.

A
  • c, e, b, a, d
5
Q

The following events take place during translation. Select the answer choice that puts them in the correct sequence.

  1. Binding of aminoacyl-tRNA to the A site.
  2. Binding of the small ribosomal subunit to the 5′ end of the mRNA.
  3. tRNA in the P site moves to the E site.
  4. Translocation of the ribosome.
  5. Peptide bond formation.
A
  • 2, 1, 5, 4, 3
6
Q

A peptide bond

A
  • forms between a carbon atom and a nitrogen atom
7
Q

The final amino acid of every polypeptide is

A
  • variable
8
Q

Which of the following statements concerning release factors is incorrect?

A
  • The release factor carries terminal amino acids

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