Molecular biologyLesson 5 of 5 in the course Genes and Proteins

Ribosomal Translation, Protein Folding, and Cellular Targeting

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Proteins are essential to nearly every cellular function, and making them uses more of a cell’s energy than any other metabolic process. A protein or protein component is built from a chain of amino acids called a polypeptide. Polypeptides can range from about 50 to more than 1,000 amino acid residues.

Each amino acid has an amino group (NH2NH_2) and a carboxyl group (COOHCOOH). A peptide bond forms when the amino group of one amino acid links to the carboxyl group of another. This reaction releases one water molecule. Ribosomes catalyze peptide-bond formation as the chain is assembled.

All flashcards

What is translation?
Translation decodes an mRNA sequence to produce a polypeptide.
What are the roles of the ribosomal subunits?
The small subunit binds mRNA; the large subunit binds tRNAs and catalyzes peptide-bond formation.
How does a tRNA connect an mRNA codon to an amino acid?
Its anticodon pairs with a complementary mRNA codon, while the tRNA carries an amino acid.
What is tRNA charging?
An aminoacyl-tRNA synthetase uses ATP to attach the appropriate amino acid to a tRNA.
What is a signal sequence?
A short protein sequence that helps direct the protein to a cellular destination.

Quiz questions

  1. What happens when a peptide bond forms between two amino acids?Answer: One amino acid's amino group links to another's carboxyl group, releasing water.
  2. Which amino acid does the initiator tRNA carry during translation initiation in *E. coli*?Answer: Formylated methionine.
  3. How does a ribosome respond when a stop codon reaches its A site?Answer: A release factor recognizes the codon and promotes polypeptide release.
  4. What does translocation do during translation elongation?Answer: It advances the ribosome by one codon along the mRNA.
  5. How do chaperones assist some newly made proteins?Answer: They help proteins fold and reduce aggregation.

Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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