pkb values!

[Potatoman1800]

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How does an increase in basicity of an amino acid residue cause a decrease in pkb? I thought since you have a more basic residue, the pkb would be favored and larger...

sorry this is really hard to put together. it was from a Kaplan test bank question about the amino acid residues on a hemoglobin.

if anyone can help that would be great, thanks.

 

[matth87]

Higher Kb means better base.
Lower pKb means better base

Higher Ka means better acid
Lower pKa means better acid

Kb = [BH][OH-]/
the higher the Kb the more BH you have in solution meaning the more protons B accepted meaning the better the base
pKb = -log(Kb) so it just another way to measure bascisity, higher Kb's will give you lower pKb's

 

[Potatoman1800]

great, thanks..i understood the concept for acids, but i can see now how it applies to bases.

 

[csulapredental]

Higher Kb means better base.
Lower pKb means better base

Higher Ka means better acid
Lower pKa means better acid

Kb = [BH][OH-]/
the higher the Kb the more BH you have in solution meaning the more protons B accepted meaning the better the base
pKb = -log(Kb) so it just another way to measure bascisity, higher Kb's will give you lower pKb's

but what exactly is "LOWER" like whats the number, the cut off to determining like OK thats low.