Amino Acids Flashcards
•organic compound containing an amino group and a carboxyl group
•colorless, nonvolatile, crystalline solids, melting and decomposing at temperatures above 200°C
Amino acids
____ amino acids
20
An amino acid in which the amino group is linked to the carbon atom next to the -COOH carbon
Alpha (a) amino acid
•Polar
›Basis for classification - four groups:
nonpolar, polar but neutral, acidic, and basic.
R groups
Nonpolar : _________ (they repel water)
hydrophobic
Polar but neutral, acidic and basic: ______ (attracted to water)
hydrophilic
Chiral (except glycine) : exists as two _______
enantiomers
L-isomer - ________
natural
The amino acids found in proteins have the same chirality as L-glyceraldehyde, which is opposite to that of
D- glyceraldehyde
Stereochemistry of alanine and glyceraldehyde
carboxylic acids
•RCOOH
•cannot exist in the presence of a moderately weak base (such as NH3)
•They donate a proton to become carboxylate ions, RCOO
Amines
•RNH2
•cannot exist in the presence of a moderately weak acid (such
as acetic acid).
•They gain a proton to become substituted ammonium ions,
RNH3
an amino acid has ______ and ______ groups in the same molecule. Therefore, in water solution, the -COOH donates a proton to the -NH2
-COOH and -NH2
compounds that have a positive charge on one atom and a negative charge on another.
zwitterions
German : zwitter ➡️ “_______”
“hybrid”
______ acids are zwitterions, not only in water solution but also in the solid state
amino acids
they are therefore ______ compounds- internal salts.
ionic
Unionized RCH(NH2 )COOH molecules
do not actually exist, in ___ form.
any
Amino acids still retain as _____ even with the addition of H,O* or NaOH to raise or lower the pH
ions
• A pH at which a sample of amino acids or protein has an equal number of positive and negative charges
Isoelectric point (pl)
Amino acids are ________ compounds, and aqueous solutions of them are buffers.
amphiprotic
Function of amino acids and proteins is determined by its _______
side chains
example: cysteine is easily sometimes by _______
mild OA
can in turn be reduced to give two molecules of cysteine
cystine
