What is the pl of glycine ? The structure and pKa values are shown below.
`H-underset(pKa=9.60)underset(darr)underset(o+)underset(NH_3)underset(|)overset(H)overset(|)C-COOHlarrpKa=2.34`

Options

A. 2.26
B. 5.97
C. 3.63
D. 11.94

Answer

To find the isoelectric point (pI) of glycine, we will use the given pKa values for the carboxyl group (pKa1 = 2.34) and the ammonium group (pKa2 = 9.60). The pI is calculated as the average of these two pKa values. Here’s a step-by-step solution:

### Step 1: Identify the pKa values
- The pKa of the carboxylic acid group (COOH) is 2.34.
- The pKa of the ammonium ion (NH3+) is 9.60.

### Step 2: Use the formula for pI
The formula for calculating the isoelectric point (pI) is:
\[ \text{pI} = \frac{\text{pKa1} + \text{pKa2}}{2} \]

### Step 3: Substitute the pKa values into the formula
Substituting the identified pKa values into the formula:
\[ \text{pI} = \frac{2.34 + 9.60}{2} \]

### Step 4: Calculate the sum of pKa values
Calculate the sum:
\[ 2.34 + 9.60 = 11.94 \]

### Step 5: Divide by 2 to find pI
Now divide the sum by 2:
\[ \text{pI} = \frac{11.94}{2} = 5.97 \]

### Final Answer
Thus, the isoelectric point (pI) of glycine is **5.97**.

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