DAT Biology Protein Structure Q: Need Clarification

[GoGreenAndFloss]

Hi all,

Can someone please help me out with this??

6. Which of the following is a type of intramolecular force that is seen in the tertiary structure of a protein, but not in the secondary structure of a protein?

• A. Subunit bonding
• B. Hydrogen bonding
• C. Peptide bonding
• D. Covalent bonding
• E. Hydrophobic interactions

Answer: E

I understand that E is correct but wouldn't D also be correct. Due to disulfide bridges which are covalently bonded. I have tried searching for this answer on google and a couple sites listed disulfide bonds as under tertiary structure only. Should I assume bootcamp wrong on this one? Or can someone provide a more thorough explanation? This frustrated me even more because in the detailed description of the problem it lists disulfide bridge as tertiary.

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[caffeine jitters]

I think the crux of that question was that it didn't specify the covalent bond as being a disulfide bond. It just referred to covalent bonds, which is a broad term that refers to many different types of interactions.

I can definitely see where you're coming from, but in a multiple choice question like this, I think letter E is definitely the best choice.

 

[joelm]

Peptide bonds (which are covalent bonds) make up the protein backbone and are seen in primary, secondary, tertiary and quaternary structure. As are the bonds between different atoms within the amino acids. Covalent bonding therefore is seen in all levels of protein structure. It'd be incorrect to choose covalent bonding as appearing in tertiary but not secondary structure. E however is correct, as you've pointed out! Let me know if this helps clarify things : )

 

[Bingwen]

Yeah I gotta agree with caffeine jitters. With tests like this it is more about the best answer rather than correct. My other thought on this too is that it is asking what is in tertiary and not secondary. I was taught that you have to consider the peptide bonds in all of the the levels which are covalent bonds.

 

[deleted738762]

I'm not sure but I'll give it a go. All proteins don't have disulfide bonds right?. Also, peptide bonds are covalent and since their present in the primary structure then they should also be present in the secondary structure because you polymerize off the monomers no? Obviously the secondary structure has it's own unique characteristics like H-bonding, but it still has peptide bonds between amino acids so they would be present in the secondary structure. I'm just theorizing here so someone can chime in, it makes sense to me, but I could be wrong.

 

[caffeine jitters]

I'm not sure but I'll give it a go. All proteins don't have disulfide bonds right?. Also, peptide bonds are covalent and since their present in the primary structure then they should also be present in the secondary structure because you polymerize off the monomers no? Obviously the secondary structure has it's own unique characteristics like H-bonding, but it still has peptide bonds between amino acids so they would be present in the secondary structure. I'm just theorizing here so someone can chime in, it makes sense to me, but I could be wrong.

Proteins will only have a disulfide bond if they have 2 or more methionine or cysteines (methionine is one of our 9 essential amino acids that we use to make cysteine; only two amino acids that have sulfur).
With the secondary structure, we're most concerned about the H-Bonding between adjacent amino/carboxyl groups, which is why we have the alpha helices and B-pleated sheets developing the way they do.
The tertiary structure is going to mainly be the intermolecular interactions between R groups of adjacent amino acids, as well as the disulfide bonds.
Then, of course, the quaternary structure is when multiple peptides come together to function as a unit.
I think the main thing we gotta remember, is that the purpose of having different levels of protien structure is for classification. So if we start applying the defining characteristics of one level to another, it all gets kinda muddy and confusing. Ya know?

 

[GoGreenAndFloss]

Thanks for the clarification everyone!

 

[deleted738762]

Proteins will only have a disulfide bond if they have 2 or more methionine or cysteines (methionine is one of our 9 essential amino acids that we use to make cysteine; only two amino acids that have sulfur).
With the secondary structure, we're most concerned about the H-Bonding between adjacent amino/carboxyl groups, which is why we have the alpha helices and B-pleated sheets developing the way they do.
The tertiary structure is going to mainly be the intermolecular interactions between R groups of adjacent amino acids, as well as the disulfide bonds.
Then, of course, the quaternary structure is when multiple peptides come together to function as a unit.
I think the main thing we gotta remember, is that the purpose of having different levels of protien structure is for classification. So if we start applying the defining characteristics of one level to another, it all gets kinda muddy and confusing. Ya know?

What you said is all true, but that's the only way the question make sense.