Pro2- Ionization and Chirality

In a solution at pH 7, free amino acids exists as ____________________ or _____________________.

dipolar ions or Zwitterions

Which one is protonated and which one is deprotonated:

NH3+ or COO-?

protonated: NH3+

deprotonated: COO-

what is the ionization state for a solution at pH7?

zero

changes in _________ will alter the Zwittterion's ionization state.

pH

What determines the degree of ionization?

PH and pka

What is occurring when Pka=pH?

50%= of functional group is acid/protonated form

50%= of functional group is conjugate base/deprotonated form

Lower the pka, ________________ the acid.

stronger

what does the pH measure?

the hydrogen ion(H+) concentration

pH=-log[H+]

what does the pka reveal?

the pH cutoff for protonation of an ionizable functional group

when is something considered protonated or deprotonated on a concentration graph?

when it is below the cutoff= protonated

when it is above the cutoff= deprotonated

carboxyl has a pka around what?

~2

amine has a pka around what?

~9

what is the charge of below pH 2?

+1 charge

what is the charge at pH 3-8?

no charge

what is the charge above pH 9?

-1 charge

True or False: Do proteins retain ionization states?

Explain why.

no proteins do not retain ionization charges because peptide bonds between carboxyl

Majority(95%) of natural-occurring proteins have what type of net charge?

low net charge

Some proteins are highly-charged, such as ________________

histones

what are 2 chemical changes that prompt chromatin modeling?

Acetylation and Phosphorylation

Because of structure, most amino acids exist in what type of forms?

two-mirror image forms

What are the 2 amino acid form structures called.

Name the differences in both structures and purposes.

L amino acids and D amino acids

L amino acids: amino acids are constituents of proteins

- eukaryotic enzymes preferentially recognize this isomer

- Amine(NH3+) located on left side, R group top right, Carboxyl(COO-) bottom right, Hydrogen top left

D amino acids: not used in proteins

- Amine(NH3+) on bottom right, Carboxyl(COO-) bottom left, top right Hydrogen, R group top left.

Most amino acids display optical isomerism due to what?

Think of what optical isomerism is.

what is the ONE amino acid exception to this?

Chirality

optical isomerism: molecular formula and connectivity are same; however the rotation/arrangement differ

Glycine

Describe what chiral means:

asymmetric in that structure and mirror image not superimposable

Chiral molecules contain 1 or more ____________________ or chiral centers.

stereocenters

Name the importances of chirality and isomers:

- fundamental component of receptor binding

-isomer selections means to maximize drug efficacy

-isomer selection helps minimize undesirable effects

what is an example of a drug that had 2 different effects due a mix up in the isomers?

Thalidomide used for pregnant women