Amino acids Flashcards
the isoelectric point of an amino acid is
the pH of an aqueous solution in which the amino acid is neutral. it is also the pH at which the zwitterion exists in aqueous solution
a zwitterion is
a molecule containing positive and negative charges but which has no overall charge. Because amino acids have both the NH2 and COOH functional groups, when they react, they form a NH3+ group and a COO- group
the general formula o an amino acid is:
H2N - CHR - COOH
where R is an alkyl group or a more complex structure including other elements and functional groups
all amino acids are chiral, except for……………….. because…………………
glycine
its structure is:
H2N - CH2 - COOH
there are over ……………. amino acids found in humans
20
proteins are made of
amino acids
all amino acids are soluble in water true/false:
true
amino acids could react as base and form an alkaline solution when reacting with water according to the equation (use R)
H2N - CHR- COOH + H2O ⇌ H3N+ - CHR - COOH + OH-
reaction as a base
an amino acid could also react as an acid and form an acidic solution with water:
H2N - CHR- COOH + H2O ⇌ H2N - CHR - COO- + H3O+
the H3O+ ion (hydronium ion) is acidic
a third reaction amino acids could undertake with water to form a zwitterion is
H2N - CHR- COOH + H2O ⇌ H3N+ - CHR - COO-
where the H+ from the COOH goes to the NH2 group
a low isoelectric point indicates that the molecule is
predominantly acidic
e.g. glutamic acid has a value of 3.2
a high isoelectric point indicates that the molecule is
predominantly basic
e.g. lysine ha d value of 9.7
the isoelectric point of an amino acid is related to
the number of NH2 and COOH groups in the molecule.
e.g. glutamic acid has 2 COOH group, hence the low isoelectric point, while lysine has two NH2 groups
the amino group is
NH2
true/false: an amino acid can form salts with acids and bases
true
