Question

During protein folding, the entropy of water: a. increases b. decreases c. is equal to the protein entropy change d. is zero

Short answer

a. increases

Step-by-step solution

Understanding Protein Folding

Protein folding is the process by which a protein structure assumes its functional shape or conformation. During this process, the hydrophobic regions of the protein tend to be buried inside, away from water, while the hydrophilic regions are exposed to the aqueous environment.

Analyzing Water's Role

In an unfolded protein, water molecules are organized around hydrophobic residues, creating a structured layer to minimize interaction with these residues. This ordered state represents a lower entropy for the water molecules.

Entropy Change During Folding

When a protein folds, the hydrophobic regions are sequestered from water, disrupting the previously structured water layer. This disruption leads to an increase in the disorder of water molecules, resulting in an increase in the entropy of the water surrounding the folding protein.

Determining the Correct Answer

Since protein folding sequesters hydrophobic residues and allows water molecules to become more disordered, the entropy of water increases during protein folding.

Key concepts

Entropy Change

Proteins fold by organizing themselves into specific shapes. This process impacts the entropy of the surrounding water molecules. Entropy is a measure of disorder or randomness in a system. During protein folding, the hydrophobic (water-repelling) regions are hidden away from water. Initially, these hydrophobic regions cause water molecules to gather in an orderly fashion around them, creating a structured environment. This ordered state is low in entropy.

When the protein folds, it effectively hides these hydrophobic regions. This action disrupts the ordered water environment, freeing water molecules to move more randomly. As a result, the level of disorder in the water increases, leading to higher entropy. In summary, during protein folding, the entropy of the surrounding water molecules increases, as the system shifts to a more disordered state.

Hydrophobic Effect

The hydrophobic effect is crucial to protein folding. It is the driving force that makes nonpolar substances, like certain parts of proteins, avoid contact with water. This effect plays an essential role in determining the structure of a protein.

Hydrophobic residues, or the water-repelling parts of a protein, aim to stay away from water. As the protein folds, these hydrophobic regions get buried within the protein's core, far from the aqueous environment. This action results in a more stable protein structure because the hydrophobic effect helps reduce the exposure of nonpolar areas to water, favoring energetically advantageous arrangements.

• Hydrophobic regions try to minimize their contact with water.
• Proteins tend to bury these regions inside during folding.
• This folding helps stabilize the final structure of the protein.

Understanding the hydrophobic effect is vital for comprehending how proteins naturally find their shape and function.

Protein Structure

Protein structure is established through a careful folding process, where the sequence of amino acids determines the final shape. Protein folding results in complex structures that define the protein's functionality.

Proteins are made up of amino acid chains. Their first level of organization is the primary structure, which is simply the sequence of amino acids. As folding progresses, proteins form secondary structures like alpha-helices and beta-sheets. Eventually, the folding completes into a unique three-dimensional shape, known as the tertiary structure, which is essential for the protein's function.

• Primary Structure: sequence of amino acids.
• Secondary Structure: alpha-helices and beta-sheets.
• Tertiary Structure: The complete 3D conformation.

This organized yet intricate folding is essential because the three-dimensional shape is closely tied to the protein's role inside the body.