Bio1332 Biochemistry - Lecture Eight - Protein Folding And Stability

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Bio1332 Biochemistry - Lecture Eight - Protein Folding And Stability - Quiz

Understand the physical basis of the various forces that hold proteins together. Understand that protein structure is determined by primary sequence. Understand that the folded native conformation is the most energetically favourable. Appreciate that protein folding is a directed process and conformations are not just cycled through until the best one is found.


Questions and Answers
  • 1. 

    Complete the following sentence:Interaction with solvent plays a major role in protein folding. Contact with solvent is _________ in a protein's unfolded state.

    Explanation
    The interaction with solvent is at its highest or maximum level in a protein's unfolded state. This means that the protein is exposed to and in close contact with the solvent molecules, which can affect the folding process. The term "most" can also be used to describe this high level of interaction. However, the phrase "at maximum" or "at most" indicates the highest possible level of interaction with the solvent in the unfolded state.

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  • 2. 

    Which of the following is true?

    • A.

      Most proteins are only stable between pH 5.0 and pH 9.0

    • B.

      Most proteins are only stable at approx neutral pH 7.0

    • C.

      Most proteins are only stable between pH 2.0 and pH 12.0

    • D.

      Most proteins are only stable between pH 6.0 and pH 8.0

    Correct Answer
    A. Most proteins are only stable between pH 5.0 and pH 9.0
    Explanation
    Most proteins are only stable between pH 5.0 and pH 9.0 because the stability of proteins is highly influenced by the pH of their environment. Proteins have specific pH ranges in which they are most stable and function properly. Outside of this pH range, proteins can undergo denaturation, leading to loss of structure and function. The pH range of 5.0 to 9.0 is considered a physiological pH range, which is close to the neutral pH of 7.0. Therefore, most proteins are stable within this range, allowing them to maintain their structure and function effectively.

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  • 3. 

    Complete the following sentence:Hydrophobic atoms have a _____ group.

    Correct Answer
    Methyl
    Explanation
    Hydrophobic atoms have a methyl group. A methyl group consists of one carbon atom bonded to three hydrogen atoms (-CH3). This group is nonpolar and does not readily interact with water molecules, making it hydrophobic.

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  • 4. 

    Complete the following sentence:Electrostatic interaction only occurs on amino acids that have a ________ charge on their side chain.

    Correct Answer
    Positive
    Explanation
    Electrostatic interaction only occurs on amino acids that have a positive charge on their side chain. This is because electrostatic interactions are attractive forces between oppositely charged particles. Amino acids with a positive charge on their side chain can form electrostatic interactions with amino acids that have a negative charge on their side chain. This interaction is important in protein folding, protein-protein interactions, and other biological processes.

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  • 5. 

    Complete the following sentence:Van der Waals interactions are non-covalent interactions between electrically ______ molecules.

    Correct Answer
    Neutral
    Explanation
    Van der Waals interactions are non-covalent interactions between electrically neutral molecules. These interactions occur due to temporary fluctuations in electron distribution, resulting in the formation of temporary dipoles. These temporary dipoles induce similar dipoles in neighboring molecules, leading to attractive forces between them. Since these interactions occur between neutral molecules, it means that the molecules involved have an equal number of positive and negative charges, resulting in no overall charge.

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  • 6. 

    True or False?Van der Waals interactions are much weaker than ionic reactions.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Van der Waals interactions are weaker than ionic reactions because they are temporary attractive forces that occur between molecules. These interactions are caused by the fluctuations in electron distribution around atoms, resulting in temporary dipoles. On the other hand, ionic reactions involve the transfer of electrons between atoms, leading to the formation of strong electrostatic attractions between positively and negatively charged ions. Therefore, the statement that Van der Waals interactions are much weaker than ionic reactions is true.

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  • 7. 

    Which of the following is true?Hydrogen bonds are...

    • A.

      Electrostatic interactions between a weak acidic donor group and an acceptor atom

    • B.

      Electrostatic interactions between a strong acidic donor group and an acceptor atom

    • C.

      Electrostatic interactions between a weak alkaline donor group and an acceptor atom

    • D.

      Electrostatic interactions between a strong alkaline donor group and an acceptor atom

    Correct Answer
    A. Electrostatic interactions between a weak acidic donor group and an acceptor atom
    Explanation
    Hydrogen bonds are electrostatic interactions between a weak acidic donor group and an acceptor atom.

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  • 8. 

    Disulfide bonds are #_____# bonds between two #______# molecules in a protein chain when they approach each other in the 3D folded structure.

    Correct Answer
    Covalent
    Cysteine
    Explanation
    Disulfide bonds are covalent bonds between two cysteine molecules in a protein chain when they approach each other in the 3D folded structure. Covalent bonds involve the sharing of electrons between atoms, and in the case of disulfide bonds, the sulfur atoms in two cysteine molecules form a covalent bond. These bonds play a crucial role in stabilizing the 3D structure of proteins and can greatly impact their function.

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  • 9. 

    Complete the following sentence:Correct protein folding is helped in the cell by other proteins called _________.

    Correct Answer
    Chaperonins
    Explanation
    Chaperonins are proteins that assist in the correct folding of other proteins in the cell. They provide a protective environment for the folding process, preventing misfolding and aggregation. Chaperonins act as molecular chaperones, ensuring that proteins fold into their proper three-dimensional structures, which is crucial for their functional activity. These proteins play a vital role in maintaining protein homeostasis and preventing the formation of protein aggregates that can lead to cellular dysfunction and disease.

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