Adenine - Uracile vs. Adenine - Thymine

[zoner]

which hybridized bond is stronger between these? one pyrimidine has a methyl group and the other one does not.

Thanks

I think methyl group donates electrons thus destabilizes the ring, making it (if it had acidic proton) less acidic or less willing to give up its proton. Wait am I right on this or is it the other way around....

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[loveoforganic]

I wouldn't expect significant differences between the two in their h-bonding. Could be wrong though. Biochem book not on campus with me

 

[zoner]

there should be. maybe not significant, but I do know that methyl group does affect it.

I was thinking,,, would a methyl group make the bond between the two stronger since its donating electrons to the ring thus giving more electrons for the bonding connection?

anyone?

 

[zoner]

urr.. anyone?

 

[ridethecliche]

Where is this coming up?

I can't picture this in any passage except if they give you two strands to make templates of and one needs a higher T to break the strands.

They don't bond covalently, they're actually held together by H bonds, so I'm really not sure how you're thinking about this. Yes, the backbone is held by covalent bonds, but that's the same for both.

A-T and A-U are both held by 2 H bonds and have the same bonding strength as all else is equal.

 

[zoner]

Where is this coming up?

I can't picture this in any passage except if they give you two strands to make templates of and one needs a higher T to break the strands.

They don't bond covalently, they're actually held together by H bonds, so I'm really not sure how you're thinking about this. Yes, the backbone is held by covalent bonds, but that's the same for both.

A-T and A-U are both held by 2 H bonds and have the same bonding strength as all else is equal.

So I am asking which H bonds are stronger between these two? one with methyl group or one without?

They could give you this kind of questions when talking about RNA vs DNA

 

[ridethecliche]

So I am asking which H bonds are stronger between these two? one with methyl group or one without?

They could give you this kind of questions when talking about RNA vs DNA

H bonds are H bonds.

Whichever ones are closer are stronger. Are you suggesting that the methy h's are involved in H bonding because I'm pretty sure they're not.

 

[Rabolisk]

They could give you this kind of questions when talking about RNA vs DNA

I doubt that.

 

[zoner]

no no,, this is a valid question raised by one of TBR instructor except that I never got to hear the answer because I came late to the class next day.

Thymine and Uracil are different because Thymine has a methyl group. They are both H bonded to Adenine in RNA or DNA. So I am asking due to that methyl group, which H bond is stronger? It can't be that all H bonds are the same strength.

 

[cheesier]

I'll give you a totally speculative answer:

A methyl group is electron donating, so it will increase electron density near the hydrogen bond. I would think that this would decrease the strength of the bond very slightly. Someone correct me if I have it backwards.

 

[zoner]

I'll give you a totally speculative answer:

A methyl group is electron donating, so it will increase electron density near the hydrogen bond. I would think that this would decrease the strength of the bond very slightly. Someone correct me if I have it backwards.

oh gawd, I was just thinking the same thing in the shower. So O is more electronegative than N, so H bond is stronger when it involves O. But since we are talking about same elements H bonding between uracil and thymine, whicheve ris more electronegative will have stronger H bond. And since the methyl group donates electrons density, thus making the element within the same pyrimidine less electronegative, thus making it have weaker H bond than pyrimidine rignt without the methyl group.

 

[cheesier]

Hmm, now I'm not so sure. Donating electrons increases the electron density which would increase the polarity of the bond. I think that it might mean that a methyl group strengthens the H bond. I hope someone else chimes in to clarify.

 

[Baller MD]

You do realize that only viral and si RNA are double stranded? mRNA, tRNA, rRNA, hnRNA and snRNA are all single stranded.

 

[loveoforganic]

There's still AU pairing in ssRNA. Zoner - ask your lecturer after class. In my OP, I didn't say there would be zero difference, just that the difference due to such a small structural change would likely be very, very minimal.

 

[ridethecliche]

Like myself and others were getting at, this is something FAR outside the scope of the MCAT and even biochemistry.

This involves crystallization and molecular modeling programs to accurately depict. Yeah, the MCAT is going to make you do that.

You are trying to read into ALL the wrong things...

 

[zoner]

Like myself and others were getting at, this is something FAR outside the scope of the MCAT and even biochemistry.

This involves crystallization and molecular modeling programs to accurately depict. Yeah, the MCAT is going to make you do that.

You are trying to read into ALL the wrong things...

Yeah, but at the same time, if you go with my reasoning, you can deduce it down to pretty simple concept as electronegativity and electron donation.

 

[Rabolisk]

You never know, this VERY QUESTION might be the difference between you getting into med school and not.

 

[zoner]

whether this kind of questions will be on the exam or not, its still an interesting concept tlo think about