McMurry (Kap.2,10) Flashcards
Practically all biological reactions involve organic acids and bases.
What defines an organic acid?
Organic acids are characterized by the presence of a positively polarized hydrogen atom, and are of two main kinds:
1) Hydrogen bonded to an electronegative oxygen (ex. methanol, acetic acid).
2) Hydrogen bonded to a carbon next to a C=O bond (O=C-C-H). Examples are acetone.
What are the acidity caused by in both examples of an organic acid?
The conjugate base of the acids, resulting from loss og H+, is stabilized by having its negative charge on an electronegative oxygen (Methanol).
In addition to that, in the example of (acetic acid), the conjugate base is further stabilized by resonance.
In the example of (acetone), the conj. base is stabilized by resonance (from placing the negative charge from carbon to oxygen).
A stable base equals a strong conjugate acid (weak base)
An unstable base equals a weak conjugate acid (strong base)
What organic acid is often seen in living organisms, and is involved in almost all metabolic pathways?
Carboxylic acids, in the forms of acetic acid, pyruvic acid and citric acids.
Practically all biological reactions involve organic acids and bases.
What defines an organic base?
They are characterized by the presence of an atom with a lone pair of electrons that can bond to a H+.
For example nitrogen containing compounds (such as methylamine) - most common and almost involved in all metabolic pathways.
Also oxygen containing compounds when reacting with strong bases - Though depending on the circumstance some oxygen compounds can react as an acid or base.
(example methanol and acetone reacts as a base when they accepts a proton, but as an acid when they donate a proton).
What are amino acids?
Building blocks for proteins in living organisms.
They are made of amines (NH2) and carboxylic acids (CO2H).
How many amino acids exist?
20
Why does amino acids exist in the “zwitterion form”?
Rather then existing in their uncharged form, they exist in the double charged form called zwitterion form.
This form arises because amino acids both have acidic and basic sites within the same molecule, and therefore undergo an internal acid-base-reaction.
