BIOCHEMISTRY Question

[tjddmskiss]

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Anyone can solve this question?

1. Which of the following statement about protein is false?
a) secondary structure is regular, recurring arrangement in space of nearby amino acid residue is a poly-peptide
b) active protein are generally very loosely structured
c) in water soluble protein, hydrophobic amino acid residues are generally buried and not exposed to water
d) quaternary structure involves the interaction of subunits in a protein with more than one polypeptide chain
e) primary structure determines tertiary structure

2. Which force contributes least to the Tertiary and quaternary structure of protein?
a) dipole dipole interaction
b) hydrophobic interaction
c) hydrogen bond
d) covalent bond
e) ionic interaction

I totally got lost for these two questions, seems like little bit tricky

 

[jimlaner]

Anyone?

 

[tjddmskiss]

I think 1 - b 2 - d

I choose covalent bond since only covalent interaction on tertiary structure is disulfide bond. I am not sure though. I really want to know right answer for the second question.

 

[yappy]

I agree with 1 B but for 2 I say A.

Why not d? disulfide bridges.

What are the ans?

 

[R1Guy]

I thinks 2 is A as well. Yes there are much fewer disulfide bonds than dipole-dipole interactions but covalent bonds are ridiculously stronger.

 

[1800RAW]

is also say #1 is definitely b, #2 is kinda tricky. if it was just tertiary structure id go with covalent bonds but alot of proteins with a quaternary structure are held together by disulfide bridges (antibodies, lots of extracellular proteins, etc.). then again, all the other forces listed are a major contribution to tertiary structure...

i dunno, id go with D but i wouldnt be very confident with that answer.

 

[rmm30]

#1 a) isn't a sentence.

 

[sbdento]

1) B
2) E, there are no metals in protein.

 

[1800RAW]

1) B
2) E, there are no metals in protein.

doesnt have to contain a metal in order for there to be ionic interactions. several AAs have amine and carboxy functional groups that, depending on the pH vs. their own pKas, may be positively or negatively charged.

OP, do you have the answer?

 

[sbdento]

doesnt have to contain a metal in order for there to be ionic interactions. several AAs have amine and carboxy functional groups that, depending on the pH vs. their own pKas, may be positively or negatively charged.

OP, do you have the answer?

The definition of an ionic bond is (almost always) between a metal and a nonmetal and in the case of the DAT will probably always be between a metal and a nonmetal. You are correct about amines and carboxy's having a charge, but I don't think the charge is strong enough to be considered ionic.

 

[1800RAW]

I dont think an ionic bond is always between a metal and nonmetal, although its certainly an accurate generalization, but rather the result of an electrostatic interaction between 2 oppositely charged species. Also, I dont think you can consider a charge to be strong/weak enough to be called ionic or not; it either is charged or it isnt. Granted in the case of acidic and basic sidechains, there wont be full de/protonation of all R groups and an equilibrium will be reached, but those molecules that do transfer protons will be fully charged ie. ions. Also campbells has a diagram in their book that describes this kind of interaction as ionic.

Then again, its also possible that im an idiot and have no idea wtf im talking about. If so someone please chime in because the last thing I wanna do is confuse someone

 

[yappy]

SO salt bridges are not considered ionic? Surely these are stronger than dipole dipole.

OP What is the answer! lol

 

[sbdento]

I dont think an ionic bond is always between a metal and nonmetal, although its certainly an accurate generalization, but rather the result of an electrostatic interaction between 2 oppositely charged species. Also, I dont think you can consider a charge to be strong/weak enough to be called ionic or not; it either is charged or it isnt. Granted in the case of acidic and basic sidechains, there wont be full de/protonation of all R groups and an equilibrium will be reached, but those molecules that do transfer protons will be fully charged ie. ions. Also campbells has a diagram in their book that describes this kind of interaction as ionic.

Then again, its also possible that im an idiot and have no idea wtf im talking about. If so someone please chime in because the last thing I wanna do is confuse someone

Looks like I'm wrong about the ionic interactions according to Campbells and this site: http://www.chemguide.co.uk/organicprops/aminoacids/proteinstruct.html
oops

 

[jimlaner]

The answer for 2nd question is B because Hydrophic interaction is not really a force.

 

[IndianaGuy]

I would say #1: B and #2: D

 

[yappy]

The hydrophobic effect in protein folding plays a huge role in tert and quat structure though... did you look up the answer?

The answer for 2nd question is B because Hydrophic interaction is not really a force.

 

[bigndog525]

1) is B

 

[rmm30]

how bout choice
f) this is a s.hitty question with no answer

 

[sbdento]

how bout choice
f) this is a s.hitty question with no answer

Unfortunately there isn't a like button on sdn.

 

[Juggernauts]

I am leaning toward
1: E. My reasoning is because it's the primary amino acid SEQUENCE, not structure that determines tertiary structure and then two or more tertiary proteins interacting that make up a quarternary structure. The primary STRUCTURE of every protein is the same. It's a linear sequence of aa's.
My only beef with answer choice B is that it is so vague. I do not know what they mean by "loosely structured." A protein structure does have bend and flexibility to it. As we all know, Secondary sequence has Hydrogen(weak) bonds down the backbone (COOH & NH2)causing alpha helix and beta sheets,and more Hydrogen (weak) bonds between the R(amino) and a disulfide(covalent) bond between the cystein aa's of the tertiary structure, this is how protein structure is formed. All you need is heat to break a hydrogen bond and a covalent bond, so I would say that a protein could very well be "loosely" structured. Just my thoughts, and I am very open to being proven wrong based some good home grown logic or the writer of the problems solution to the question would suffice.
2: E.