Organic Chemistry
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Is the following statement true or false?
The amino acid with the lowest pI value is alanine.
How much of the ⍺-amino group of serine is protonated at its isoelectric point (pI)?
The pI of glutamic acid is equal to the average pKa of its two negatively charged carboxyl groups. Explain.
Draw the structure of the prominent form of lysine (PI 9.7) present at pH values of 6, 9.7, and 12.
i. Aspartic acid has an isoelectric point at pH 2.8. Draw its most prominent forms at pH levels 1, 2.8, 5, and 11.
ii. Explain why the carboxylic side chain of aspartic acid is less acidic than its carboxylic acid near the α-carbon atom.
Determine whether valine (pI = 6.02) or cysteine (pI = 5.15) has a more negative charge at pH 7.0.
Explain why glutamic acid (pI = 3.08) elutes before threonine (pI = 5.60) when their solution having pH 5 is passed through a cation-exchange column.
Explain why cysteine (pI = 5.15) elutes before isoleucine (pI = 5.60) when their solution having pH 5 is passed through a cation-exchange column.
Determine whether alanine (pI = 6.11) or serine (pI = 5.70) has a higher percentage of negative charge at pH 7.0.
Show how electrophoresis can separate glutamic acid (PI 3.2), lysine (PI 9.7), and glycine (PI 6.0) from a solution having pH 6.