Lecture 21 – Protein structure: Quaternary structure and folding
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Questions and Answers

What characterizes the quaternary structure of a protein?

  • It is a single polypeptide chain.
  • It involves multiple polypeptide chains. (correct)
  • It only includes alpha-helices.
  • It is independent of secondary structure.

What is the function of GAPDH in its tetrameric form?

  • It is catalytically inactive.
  • It is catalytically active. (correct)
  • It has no cellular functions.
  • It is a structural protein.

What is the primary sequence of collagen?

  • Gly-X-Y (correct)
  • Pro-Gly-X
  • Gly-Pro-His
  • X-Y-Gly

What modification of proline is required for collagen synthesis?

<p>Hydroxylation (A)</p> Signup and view all the answers

What is the typical structure of collagen?

<p>Trimer (C)</p> Signup and view all the answers

Which of the following proteins was used in Christian Anfinsen's experiment on protein folding?

<p>RNAse (C)</p> Signup and view all the answers

What does Anfinsen's experiment demonstrate about protein folding?

<p>The native structure is determined by the protein sequence (B)</p> Signup and view all the answers

What reagent did Anfinsen use to disrupt hydrogen bonds and hydrophobic interactions?

<p>8M Urea (C)</p> Signup and view all the answers

What happens during the dialysis step of Anfinsen's experiment?

<p>Small molecules are removed. (B)</p> Signup and view all the answers

What is a major problem associated with unfolded proteins in the cell?

<p>They tend to aggregate due to exposed hydrophobic surfaces. (B)</p> Signup and view all the answers

What role do chaperones play in protein folding?

<p>They help prevent misfolding and aggregation. (C)</p> Signup and view all the answers

What is required for chaperones to change their conformation during the protein folding process?

<p>pH change (C)</p> Signup and view all the answers

Where is Protein Disulfide Isomerase (PDI) primarily found?

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

What is the consequence of protein misfolding?

<p>It can lead to diseases. (B)</p> Signup and view all the answers

What is the function of GAPDH as a monomer?

<p>It has no cellular function. (B)</p> Signup and view all the answers

Which of the following statements is true regarding quaternary structure?

<p>Not all proteins exhibit quaternary structure. (B)</p> Signup and view all the answers

Which condition favors protein folding in the cell?

<p>Low concentration of proteins (B)</p> Signup and view all the answers

What is the role of disulfide bridges in proteins?

<p>They stabilize the tertiary structure. (B)</p> Signup and view all the answers

What happens to a protein when urea is removed in Anfinsen's experiment?

<p>It refolds spontaneously. (C)</p> Signup and view all the answers

What type of protein is collagen classified as?

<p>Structural protein (B)</p> Signup and view all the answers

How does the sequence of amino acids affect protein folding?

<p>It determines the native structure. (C)</p> Signup and view all the answers

What is a key feature of chaperone proteins?

<p>They assist in proper protein folding. (C)</p> Signup and view all the answers

Which of the following does NOT promote protein aggregation?

<p>Proper folding (C)</p> Signup and view all the answers

What is the significance of the hydroxyproline modification in collagen?

<p>It is essential for structural integrity. (C)</p> Signup and view all the answers

What type of protein structure is most commonly associated with enzymes?

<p>Tertiary structure (C)</p> Signup and view all the answers

Which of the following best describes the term "homo-tetramer"?

<p>A protein composed of four identical polypeptide chains (B)</p> Signup and view all the answers

What is the primary consequence of exposing hydrophobic regions on unfolded proteins?

<p>They promote aggregation. (B)</p> Signup and view all the answers

Which factor is essential for protein disulfide bond formation in the endoplasmic reticulum?

<p>Oxidising environment (C)</p> Signup and view all the answers

What does the term "native structure" refer to in protein folding?

<p>The functional, folded form of a protein (B)</p> Signup and view all the answers

Which of the following is a common consequence of protein misfolding diseases?

<p>Aggregation of misfolded proteins (C)</p> Signup and view all the answers

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