Question

The isoelectric point of glutamic acid is ______.

(round off to two decimal places)

Answer 1

Correct Answer: 3.21 - 3.23

Isoelectric Point of Glutamic Acid 

The isoelectric point (\( pI \)) of an amino acid is the pH at which the molecule carries no net electric charge. For glutamic acid, the equation to find \( pI \) involves averaging the \( pK_a \) values of the acidic groups:

Step 1: Identify the relevant \( pK_a \) values for deprotonation:

• \( pK_{a1} \) (α-carboxyl group) = 2.19
• \( pK_{a2} \) (side-chain carboxyl group) = 4.25

Step 2: Compute the average of these values for \( pI \):

The equation for \( pI \) is:

\[ pI = \frac{pK_{a1} + pK_{a2}}{2} = \frac{2.19 + 4.25}{2} = 3.22 \]

Step 3: Verify the result:

The computed \( pI \) value of 3.22 is within the specified range of 3.21 to 3.23, confirming its correctness.

Final Answer:

Thus, the isoelectric point of glutamic acid, rounded to two decimal places, is 3.22.