Lecture 21 – Protein structure: Quaternary structure and folding

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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?

Hydroxylation Signup and view all the answers

What is the typical structure of collagen?

Trimer Signup and view all the answers

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

RNAse Signup and view all the answers

What does Anfinsen's experiment demonstrate about protein folding?

The native structure is determined by the protein sequence Signup and view all the answers

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

8M Urea Signup and view all the answers

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

Small molecules are removed. Signup and view all the answers

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

They tend to aggregate due to exposed hydrophobic surfaces. Signup and view all the answers

What role do chaperones play in protein folding?

They help prevent misfolding and aggregation. Signup and view all the answers

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

pH change Signup and view all the answers

Where is Protein Disulfide Isomerase (PDI) primarily found?

Endoplasmic reticulum Signup and view all the answers

What is the consequence of protein misfolding?

It can lead to diseases. Signup and view all the answers

What is the function of GAPDH as a monomer?

It has no cellular function. Signup and view all the answers

Which of the following statements is true regarding quaternary structure?

Not all proteins exhibit quaternary structure. Signup and view all the answers

Which condition favors protein folding in the cell?

Low concentration of proteins Signup and view all the answers

What is the role of disulfide bridges in proteins?

They stabilize the tertiary structure. Signup and view all the answers

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

It refolds spontaneously. Signup and view all the answers

What type of protein is collagen classified as?

Structural protein Signup and view all the answers

How does the sequence of amino acids affect protein folding?

It determines the native structure. Signup and view all the answers

What is a key feature of chaperone proteins?

They assist in proper protein folding. Signup and view all the answers

Which of the following does NOT promote protein aggregation?

Proper folding Signup and view all the answers

What is the significance of the hydroxyproline modification in collagen?

It is essential for structural integrity. Signup and view all the answers

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

Tertiary structure Signup and view all the answers

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

A protein composed of four identical polypeptide chains Signup and view all the answers

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

They promote aggregation. Signup and view all the answers