# General Biochemestry Calculations

GENERAL BIOCHEMISTRY Problem Set No. 1 Answered by: Andrea Rose A. Fajardo of BSFT 2-1N 1. Calculate the pH of a adulterate band-aid that contains a molar arrangement of potassium acetate to acerb acerbic (pKa=4. 76) of: a. 2:1 pH = 4. 76 + log/ = 4. 76 + 0. 3010 = 5. 06 b. 1:4 pH = 4. 76 + log/ = 4. 76 + (-0. 6021) = 4. 16 c. 6:5 pH = 4. 76 + log/ = 4. 76 + 0. 0792 = 4. 81 d. 2:3 pH = 4. 76 + log/ = 4. 76 + (-0. 1761) = 4. 58 e. 9:1 pH = 4. 76 + log/ = 4. 76 + 0. 9542 = 5. 71 2. A absorber contains 0. 01mol of lactic acerbic (pKa=3. 86) and 0. 05mol of sodium lactate per liter. a. What is the consistent pH of the buffer? H = 3. 86 + log[0. 05]/[0. 01] = 3. 86 + 0. 6990 = 4. 56 b. Calculate the change in pH back 5mL of 0. 5M HCl is added to 1L of buffer. 5mL of 0. 5 mol/L 5mL * 1L/1000mL = 0. 005L 0. 005L * 0. 5 mol/L = 0. 0025mol NaC3H5O3 = 0. 05mol - 0. 0025mol = 0. 0475 C3H5O3 = 0. 01mol - 0. 0025mol =0. 0075 pH = 3. 86 + log[0. 0475]/[0. 0075] = 3. 86 + 0. 8016 = 4. 66 • 4. 55-4. 66 = 0. 11 is the change in pH c. What pH change would you apprehend if you added the aforementioned abundance of HCl to 1L of authentic water? [H+] = (0. 0025mol)(1L) = 0. 0025M pH = -log 0. 0025 = 2. 60 3. The anatomy of the amino acerbic of isoleucine is accustomed at the right. a. How abounding chiral centers does it have? 2 b. How abounding optic isomers? 4 c. Draw the angle formulas for all the optical isomers of isoleucine. [pic] 4. A peptide has the sequence: Glu-His-Trp-Ser-Leu-Arg-Pro-Gly a. What is the allegation of the molecules at pH 4 and 11? (Use pKa ethics of those in the ppt) |pH |NH3+ |Glu |His |Arg |COO- |Net Allegation | |4 |+1 |-1 |0 |+1 |-1 |0 | |11 |0 |-1 |0 |+1 |-1 |-1 | . What is the pI for the peptide? | |pKaCOOH |pKaNH3 |pKaR | |Glu |2. 19 |9. 67 |4. 25 | |His |1. 82 |9. 17 |6. 04 | |Trp |2. 83 |9. 39 | | |Ser |2. 1 |9. 15 | | |Gly |2. 34 |9. 60 | | |Leu |2. 63 |9. 60 | | |Arg |2. 17 |9. 04 |12. 48 | |Pro |1. 99 |10. 60 | | |Gly |2. 4 |9. 60 | | 2. 34 6. 04 9. 67 12. 48 pI = 6. 04 + 9. 67 / 2 = 7. 85 5. Histidine has three ionisable anatomic groups. Write the calm equations for its three ionizations and accredit the able pKa for anniversary ionization. Draw the anatomy of histidine in anniversary ionization state. What is the net allegation of the histidine molecules in anniversary ionization state? STRUCTURE OF IONIZATION IN EACH IONIZATION STATE [pic] NET CHARGE Anatomy |Net Allegation | |+H3N--CH--(RH+)--COOH |+2 | |+H3N--CH--(RH+)--COO- |+1 | |+H3N--CH--(R)--COO- |0 | |H2N--CH--(R)--COO- |-1 | ----------------------- -2 +1 +2 -1 0

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