Amino Acids: Properties and pKa Values

This video tutorial explains how to calculate the isoelectric point (pI) of amino acids using examples of glycine, lysine, and tyrosine. It covers the concept of pKa values, the formation of zwitter ions, and the calculation of pI by averaging relevant pKa values. The video provides a step-by-step guide to understanding the dominant forms of amino acids at different pH levels and determining the pI for each example.

What is the pKa value of the carboxylic acid group in glycine?

• 7.0

• 5.5

• 9.6

• 2.3

At what pH is glycine fully protonated?

• Exactly 5.5

• Greater than 9.6

• Between 2.3 and 9.6

• Less than 2.3

Which structure represents the zwitterion form of glycine?

• Structure A

• Structure B

• Structure C

• None

What type of amino acid is lysine?

• Polar

• Acidic

• Nonpolar

• Basic

What is the pKa value of the amino group in lysine?

• 8.95

• 9.6

• 2.18

• 10.5

What is the isoelectric point of lysine?

• 7.2

• 6.8

• 9.7

• 5.5

What is the pKa value of the carboxylic acid group in tyrosine?

• 2.2

• 9.1

• 8.95

• 10.5

What is the isoelectric point of tyrosine?

• 5.65

• 7.0

• 6.5

• 9.72

Which group in tyrosine has a pKa around 10.5?

• Carboxylic acid

• R group

• Amino group

• Hydroxyl group

What is the net charge of tyrosine at a pH below 2.2?

• -2

• -1

• 0

• +1