Amino Acids and Polypeptide Chains
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Questions and Answers

What type of bonding stabilizes the α-helix?

  • electrostatic bonding
  • ionic bonding
  • hydrogen bonding (correct)
  • covalent bonding

    • What is the primary structure of keratins?

  • β-bend
  • α-helical (correct)
  • β-pleated sheet
  • random coil

    • Why does proline disrupt an α-helix?

  • It forms ionic bonds with other amino acids
  • Its secondary amino group is geometrically compatible with the right-handed spiral of the α-helix
  • It has a bulky side chain
  • Its secondary amino group is not geometrically compatible with the right-handed spiral of the α-helix (correct)

    • What type of amino acids can interfere with the formation of an α-helix?

    <p>All of the above</p> Signup and view all the answers

    What is a characteristic of β-sheets?

    <p>All peptide bond components are involved in hydrogen bonding</p> Signup and view all the answers

    What is the arrangement of β-strands in an antiparallel β-sheet?

    <p>The N-terminal and C-terminal ends of the β-strands alternate</p> Signup and view all the answers

    What is the function of β-bends?

    <p>To join two units of secondary structures</p> Signup and view all the answers

    What is the secondary structure that myoglobin has?

    <p>α-helical</p> Signup and view all the answers

    What is the correct order of reading an amino acid sequence?

    <p>From the N-terminal to the C-terminal end</p> Signup and view all the answers

    What type of interactions occur between negatively charged groups and positively charged groups?

    <p>Ionic interactions</p> Signup and view all the answers

    What is the term used to describe proteins that consist of multiple polypeptide chains?

    <p>Multi-subunit protein</p> Signup and view all the answers

    What is the level of protein structure that describes the sequence of amino acids?

    <p>Primary structure</p> Signup and view all the answers

    What is the characteristic of fibrous 3D structure?

    <p>Less folded and more extended</p> Signup and view all the answers

    What is the type of bond that keeps the entire peptide in a rigid planar configuration?

    <p>Peptide bond</p> Signup and view all the answers

    What is the term for the arrangement of polypeptide subunits in a protein?

    <p>Quaternary structure</p> Signup and view all the answers

    What is an example of a protein with a dimeric quaternary structure?

    <p>Insulin</p> Signup and view all the answers

    What is the term used to describe the local conformation of a part of a polypeptide?

    <p>Secondary structure</p> Signup and view all the answers

    What is the result of mild denaturation of a protein?

    <p>Disruption of tertiary or quaternary structures</p> Signup and view all the answers

    What is the most common type of secondary structure in proteins?

    <p>α-Helix</p> Signup and view all the answers

    What is the shape of the α-helix?

    <p>Spiral</p> Signup and view all the answers

    What is an example of a physical agent of denaturation?

    <p>Heat</p> Signup and view all the answers

    What is the result of abnormalities in the amino acid sequences of proteins?

    <p>Genetic diseases</p> Signup and view all the answers

    What is a characteristic of denatured proteins?

    <p>They are more easily digested</p> Signup and view all the answers

    What is the result of harsh denaturation conditions on a protein?

    <p>Fragmentation of the chain</p> Signup and view all the answers

    What is the composition of amyloid proteins?

    <p>Aggregates of twisted β-pleated sheet fibrils</p> Signup and view all the answers

    What is the result of protein accumulation in tissues and organs?

    <p>Severe disruption of normal physiological processes</p> Signup and view all the answers

    In which of the following conditions can amyloid deposit be produced?

    <p>Chronic inflammatory diseases</p> Signup and view all the answers

    What is the purpose of protein turnover?

    <p>To maintain constant protein content in healthy adults</p> Signup and view all the answers

    How much protein is hydrolyzed and resynthesized daily?

    <p>300-400 g/day</p> Signup and view all the answers

    What determines the rate of protein degradation?

    <p>Half-life of the protein</p> Signup and view all the answers

    Which peptide is 200 times sweeter than sucrose and used as a low-calorie artificial sweetener?

    <p>Aspartame</p> Signup and view all the answers

    What is the significant function of Glutathione in proteins?

    <p>Prevents the oxidation of sulfhydryl (SH) groups to disulfide (SS) groups</p> Signup and view all the answers

    Which hormone is produced by the posterior pituitary gland and stimulates the kidney to retain water?

    <p>Vasopressin (ADH)</p> Signup and view all the answers

    What role do molecular chaperones play in protein folding?

    <p>They bind reversibly to unfolded polypeptide segments to prevent misfolding.</p> Signup and view all the answers

    What structure is predominantly found in proteins in persons with amyloidosis?

    <p>Beta-pleated sheet</p> Signup and view all the answers

    What does the process of protein folding seek to achieve?

    <p>Low-energy state</p> Signup and view all the answers

    Which peptide causes contraction of the uterus?

    <p>Oxytocin</p> Signup and view all the answers

    What is the common result of protein misfolding?

    <p>Formation of long, fibrillar protein assemblies</p> Signup and view all the answers

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