Biology: Amino Acids and Proteins
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Questions and Answers

Which of the following best describes phenylalanine?

  • A branched-chain amino acid
  • Contains a sulfhydryl group
  • Contains a hydroxyl group
  • An aromatic amino acid (correct)
  • A dietary nonessential amino acid

    • Which of the following amino acids is most likely a precursor of the neurotransmitter GABA?

  • Aspartate
  • Tryptophan
  • Glutamine
  • Glutamate (correct)
  • Tyrosine
  • Glycine

    • A researcher is studying the secondary structure of an enzyme involved in intermediary metabolism. He observes that it contains alpha-helices. Which of the following best describes this structure?

  • A structure favored by a high amount of proline residues
  • Stabilized by peptide bonds
  • Contains amino acids with their side chains towards the outside of the helix (correct)
  • Retained when the protein is heated to high temperatures
  • Stabilized by phosphodiester linkages

    • A research group is studying covalent bonds which are formed by the side chains of amino acids. Which of the following bonds is most likely being studied by this research group?

    <p>Disulfide bonds between two cysteine residues (A)</p> Signup and view all the answers

    Which of the following best describes gene expression in bacteria?

    <p>Some internal AUG sequences must be recognized as start codons (B)</p> Signup and view all the answers

    Which of the following positions best indicates the first nucleotide of the anticodon?

    <p>5 (D)</p> Signup and view all the answers

    A research laboratory studies a disease-causing gene that leads to loss of function of an enzyme in a metabolic pathway. Karyotyping and DNA microarray shows that the chromosome structure is unchanged. Northern blot analysis shows no change in the mRNA transcript of the gene. Western blot shows a smaller than normal protein is formed.

    <p>One base pair insertion in an exon (B)</p> Signup and view all the answers

    Which of the following modifications is most likely observed during the process of primary insulin translation product undergoing modifications to produce the mature insulin hormone?

    <p>Hydrolytic cleavage of specific peptide bonds (E)</p> Signup and view all the answers

    A researcher has developed a bacterial strain in the laboratory with reduced rates of translation. It has a mutation which confers decreased activity in peptide bond formation during ribosomal protein synthesis. A Mutation in which of the following is most consistent with these findings?

    <p>One of the ribosomal RNAs (A)</p> Signup and view all the answers

    Which of the following codon changes best explains the loss of an important alpha-helical segment of the protein?

    <p>CUC to CCC (A)</p> Signup and view all the answers

    Which of the properties of the code in the novel organism is most likely different from the terrestrial (earth) genetic code?

    <p>The genetic code was overlapping (D)</p> Signup and view all the answers

    Which of the following processes is most likely inhibited by the antibiotic erythromycin?

    <p>The translocation step of translation in bacteria (D)</p> Signup and view all the answers

    Flashcards

    Phenylalanine

    An aromatic amino acid that is essential in diet.

    GABA precursor

    Glutamate can be decarboxylated to form GABA.

    Alpha-helix

    A secondary structure of proteins stabilized by hydrogen bonds.

    Covalent bond in proteins

    Disulfide bonds formed between cysteine side chains.

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    Polycistronic mRNA

    A single mRNA that encodes multiple enzymes in bacteria.

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    Anticodon

    The tRNA region that pairs with mRNA codons during translation.

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    Mutation effects on mRNA

    Insertions in exons may not change mRNA structure.

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    Insulin modification

    Involves hydrolytic cleavage to become functional insulin.

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    Translation inhibition by erythromycin

    Inhibits translocation during peptide synthesis in bacteria.

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    Codon usage

    Different codons can code for the same amino acid (degeneracy).

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    Overlapping genetic code

    A characteristic likely different in the Martian organisms.

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    Ribosomal RNA function

    Catalytic RNA that facilitates peptide bond formation.

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    Hydrophobic interactions

    Noncovalent forces driving hydrophobic amino acids together.

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    Signal peptide

    Leads to the cleavage for mature protein synthesis.

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    Frameshift mutation

    Caused by base pair insertion or deletion leading to altered reading frame.

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    Degenerate codons

    Multiple codons that specify the same amino acid.

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    Transcription inhibitors

    Compounds that prevent mRNA synthesis from DNA.

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    Chorismate

    Intermediate in the synthesis pathways for certain amino acids.

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    Disulfide bond

    Covalent bond formed between sulfur atoms in cysteine residues.

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    Polypeptide modifications

    Post-translational alterations that affect final protein form.

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    Ribosomal protein synthesis

    Process involving elongation factors during translation.

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    Eukaryotic vs prokaryotic translation

    Bacteria have formyl-methionine; eukaryotes use methionine.

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    Gene expression regulation

    Control over the transcription and translation of genes.

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    Protein denaturation

    Loss of protein structure due to heat or pH changes.

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    AUG start codon

    Initiates protein synthesis by providing methionine.

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    Amino acid side chains

    Determine the properties and function of proteins.

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    Study Notes

    Practice Questions: Translation, Amino Acids, and Proteins

    • Question 1: Aspartame, an artificial dipeptide sweetener, contains phenylalanine. Phenylalanine is an aromatic amino acid.

    • Question 2: GABA (gamma-aminobutyric acid) is formed by decarboxylating glutamate.

    • Question 3: Enzyme secondary structure, specifically alpha-helices, is stabilized by hydrogen bonds. R-groups face outwards in alpha-helices.

    • Question 4: Covalent bonds in tertiary protein structure are most likely formed by disulfide bonds between cysteine residues.

    • Question 5: E. coli gene expression for tryptophan synthesis is polycistronic, meaning one mRNA will produce multiple enzymes.

    Further Questions and Explanations

    • Question 6: Figure indicates the first nucleotide of the anticodon is position 5.

    • Question 7: A smaller-than-normal protein, unchanged mRNA transcript, and unchanged chromosome, suggests a base-pair insertion within an exon.

    • Question 8: Insulin modifications after synthesis include peptide bond cleavage.

    • Question 9: Reduced rates of translation are consistent with mutations in ribosomal proteins or ribosomal RNA.

    • Question 10: A codon change from CUC to CCC (results in an altered amino acid) would cause a loss of an important alpha-helical segment.

    • Question 11: The Martian code likely differs in the amino acid that is assigned to certain codons from terrestrial genetic codes.

    • Question 12: Erythromycin inhibits bacterial protein synthesis at the translocation step of elongation.

    • Additional Practice Questions: The indicated pages in Lippincott's Biochemistry textbook provide more practice questions covering DNA structure and replication, RNA structure, synthesis, and processing.

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    Practice Questions - Translation & Amino Acids Proteins PDF

    Description

    Test your knowledge on translation, amino acids, and protein structure with this quiz. Explore concepts such as dipeptide sweeteners, enzyme structures, and gene expression in E. coli. Perfect for students studying biochemistry and molecular biology.

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