Protein Denaturation Question

[shefv]

Can someone explain how the hydrophobic bonds would increase? I thought that when proteins denature due to heat or pH, the amount of bonds between them decreases since the bonds are broken.

There is a protein sample in a flask for your upcoming science experiment. Which of the following will occur in the sample if you place the flask on top of a Bunsen burner?

1. Proteins in the sample will denature
2. Hydrophobic interactions of the molecules in the sample will increase
3. Both A and B
4. Neither A nor B

(C) Increasing the temperature of the sample will change the protein structures and lead to the loss of physical properties. Hydrophobic interactions will increase because the active globular proteins will fold, releasing water molecules to the environment.

AND

Conformational stability of proteins is involved with free energy difference between the native folded state and unfolded state. Which of the following factor can break the stability of a protein by breaking the hydrogen bonds?

1. Chemicals
2. Enzymes
3. pH
4. All of the above

(A) Different chemicals can disrupt hydrogen bonds that hold the protein structure together. However, since the primary structure is held together by only peptide bond, it will not get disrupted.

Wouldn't enzymes and pH changes also disrupt the H bonds?

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[SkyJumper42]

1) So you understand proteins will denature. Next, lets say we have a folded protein ok? It is 100 meters long and we have different points all over the protein the have hydrophobic bonds which make them happy in their folded, isolated parts of the protein. Now we denature the protein and we have these hydrophobic regions exposed to this environment they don't like. Without the bonding and folding of a protein, these hydrophobic parts will find each other and clump together. Kind of like how oil (hydrophobic) and water separate out when mixed together.

2) I would agree with you that pH and enzymes would disrupt hydrogen bonds.

 

[amy_k]

pH changes can definitely denature proteins. At low pH the hydrogen bonds formed by carboxylate groups would be disrupted whereas at high pH the hydrogen bonds formed by amino groups would be disrupted.

 

[amy_k]

enzymes are themselves proteins so their own amino acid residues could interact with and interfere with other proteins' hydrogen bonds, though this is a pretty vague question, I'd say all of the above.

 

[kingtal0n]

an someone explain how the hydrophobic bonds would increase? I thought that when proteins denature due to heat or pH, the amount of bonds between them decreases since the bonds are broken.

A functional protein is most likely highly organized. Many of the internal hydrophobic regions (if there are any) are kept apart because they serve a functional role, their interactions are reserved for whichever molecule they are designed to find and work with. If you alter the shape of this example protein by denaturing it, then the structure will no longer be organized, the internal hydrophobic regions may collapse on themselves, forming a globular non functional mess that the body now needs to clean up.

The more disorganized the protein the more it will likely stick to itself, a dangerous entity to have floating around a cell compartment... as it could stick to other proteins and structures, and cause a disaster.

 

[Axes]

1.) Basically when a protein forms, it folds so as to expose hydrophilic regions to the surrounding aqueous solution and keep hydrophobic regions away from the surrounding water. When we denature this protein via heat, the internally folded hydrophobic regions may become exposed as the protein becomes misshapen, and thus hydrophobic interactions between these regions and the surrounding aqueous solution will increase. Tricky question.

2.) Where is this question from? "Chemicals?" Not a scientific use of that word, in my opinion. pH should have more of an effect of ionic bonds, but is maybe still relevant to H bonds at extremes. I agree with the previous poster in that the "enzyme" option is ambiguous; there may not be enzymes that specifically function to denature proteins, but incorrect protein protein interaction could definitely do it, case in point prions. Poor question, imo.