Cell BIo QUESTION HELP PLEASE

[americanangel]

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Okay here's the deal:
A protein has several levels of structure. Does the foramtion of these structures require energy input by the cell? If so which levels?

 

[HessExpress]

well if i'm correct i believe the only level that requires energy input, via ATP, is the primary structure. A phosphate group attaches to the COO- making the amino acid closer to the transition state in energy terms, then the condensation step occurs. I don't believe any other structure of proteins requires energy input since they are all non-covalent bond interactions. Maybe the exception is disulfide bonds, which are convalent - i'm not sure if the reducing agents involved in this require energy input.

 

[daffy]

Okay here's the deal:
A protein has several levels of structure. Does the foramtion of these structures require energy input by the cell? If so which levels?

How many structures in a protein?
1' - polipeptide bonds
2' - alpha & beta bonds
3' - 3D structure, bonds btw neighbouring atoms, S bridges
4' - if more than one subunit present, bonds btw different subunits

Now the real question - does bond forming require energy? this is your answer

good luck to all

 

[Uegis]

Okay here's the deal:
A protein has several levels of structure. Does the foramtion of these structures require energy input by the cell? If so which levels?

polypeptides does have various structures. Anyone correct me if I am wrong, but there are electrostatic, hydrophobic, and disulfide bridges from cysteine that mainly attributes to the strucutres.

Hydrophobic forces is rendered by the composition of the peptides and helps to exclude water, so i don't think this requires energy.

Disulfide bridgess are formed, so may require energy.

I'm not sure about the electrostatic forces (+ve and -ve charges on peptides, which is also related to hydrophobicity to a certain degree)

Edit: Oh yea, forgot about primary structure, peptide bonds require energy.

 

[cmb81]

Okay here's the deal:
A protein has several levels of structure. Does the foramtion of these structures require energy input by the cell? If so which levels?

just formation of primary primary structure...secondary is by hydrogen bonding....tertiary is by disulfide, hydrogen, and ionic bonds.

 

[liverotcod]

Primary structure requires ATP (think of the decrease in entropy!), but all other levels are the result of exergonic processes. The final folded form of a protein is about as stable as it can get.

 

[americanangel]

This is what I thought...
The primary structure would require energy b/c of translation. The seconardy structre with teh alpha helix and beta sheet, well that happens because of H-bonding, which is spontaneous between the amino and carboyxl groups. The tertiary structure modifies that 3D structure with additional H-bonding, van der Wall interactions, disulfide bridges, ionic bonds and hydrophobic interactions. Then the quaternary is a combination of two or more polypeptide. Now since a protein can usually regenerate itself spontaneously after degeneration, the final two structures wouldn't require energy. But to make bonds a certain amount of energy is needed even if it is negligable...
I don't know...do you guys think I'm on the right track

 

[liverotcod]

This is what I thought...
The primary structure would require energy b/c of translation. The seconardy structre with teh alpha helix and beta sheet, well that happens because of H-bonding, which is spontaneous between the amino and carboyxl groups. The tertiary structure modifies that 3D structure with additional H-bonding, van der Wall interactions, disulfide bridges, ionic bonds and hydrophobic interactions. Then the quaternary is a combination of two or more polypeptide. Now since a protein can usually regenerate itself spontaneously after degeneration, the final two structures wouldn't require energy. But to make bonds a certain amount of energy is needed even if it is negligable...
I don't know...do you guys think I'm on the right track

In all cases, bond formation is exothermic while bond breaking is endothermic. An overall reaction couples the endothermic and exothermic parts of the reaction to generate a final delta H related to the stability of the structures: more stable = more spontaneous. Then, to figure delta G, you have to think about gain or loss of entropy.

 

[americanangel]

Thanks so much everybody!!!!

 

[TTSD]

Think favorable energy states.

Exothermic and Endothermic. Like if I shoved this glass pipe up Mister slave's @$$ and put Lemmiwinks up there. =D

 

[liverotcod]

Think favorable energy states.

Exothermic and Endothermic. Like if I shoved this glass pipe up Mister slave's @$$ and put Lemmiwinks up there. =D

I think you should use an odd-petaled flower in your sig.

That was one of my fave South Parks, BTW.

 

[Dr. N]

Okay here's the deal:
A protein has several levels of structure. Does the foramtion of these structures require energy input by the cell? If so which levels?

Well, I would think that folding of the protein into its natural form does not require any ATP input at all, because it is spontaneous process. On the other hand to unfold the protein does require energy input.

 

[Medikit]

They all can require energy, but the primary structure always requires energy

 

[MEG@COOL]

Part of what makes protein folding in a cell thermodynamically favorable is that it increases entropy of the surrounding aqueus media by reducing the surface area of protein and thus allowing the water to form either less h bonds with the protein or less of a "shell" around the hydrophobic parts.

 

[ChyLn]

I don't know if this is thinking too far... but the folding of a protein is almost never just a protein by itself folding itself up. There are almost always other proteins around, chaperone proteins, etc, that make sure the protein folds correctly in case it misfolds, etc. This process, I'm sure, requires input of energy.