Absolutely, let's break this down step-by-step for **lysine** at **pH 5**. --- ## Background: Lysine Structure and pKa Values Lysine is an amino acid with three ionizable groups: - **α-carboxyl group (COOH)**, pKa ≈ 2.2 - **α-amino group (NH₃⁺)**, pKa ≈ 9. - **Side-chain amino group (NH₃⁺ on the R group)**, pKa ≈ 10.5 --- ## a. **Draw the Ionization States for Lysine at pH 5** ### At pH 5: - **Carboxyl group (pKa ≈ 2.2):** Deprotonated (COO⁻) - **α-Amino group (pKa ≈ 9.):** Protonated (NH₃⁺) - **Side-chain amino group (pKa ≈ 10.5):** Protonated (NH₃⁺) **Structure:** ``` H2N-(CH2)4-CH(NH3+)-COO- | (side-chain NH3+) ``` **Drawn form:** - **N-terminal:** NH₃⁺ - **C-terminal:** COO⁻ - **Side chain:** NH₃⁺ --- ## b. **What are the charge(s) for the ionization state(s) for lysine at pH 5?** Add up the charges: - **α-Carboxyl (COO⁻):** -1 - **α-Amino (NH₃⁺):** +1 - **Side-chain amino (NH₃⁺):** +1 **Net charge:** (+1) + (+1) + (-1) = **+1** --- ## c. **What is the concentration(s) of the ionization state(s) at pH 5?** ### At pH 5: - Both amino groups are protonated (very little deprotonation at pH 5, since their pKa values are 9 and 10.5) - Carboxyl group is deprotonated **Therefore:** Nearly all lysine molecules (>99%) are in the +1 charge state at pH 5. **Concentration of this state:** You have a .1 M solution. **So, concentration of lysine in the +1 state = .1 M** **Other ionization states (neutral, -1, etc.) are negligible at pH 5.** --- ## **Summary Table** | Group | pKa | State at pH 5 | Charge | |---------------------|-------|-----------------|--------| | α-Carboxyl | ≈2.2 | COO⁻ | -1 | | α-Amino | ≈9. | NH₃⁺ | +1 | | Side-chain (R) NH₂ | ≈10.5 | NH₃⁺ | +1 | | **Net charge** | | | **+1** | --- Let me know if you'd like me to draw the actual chemical structure!