Biochemistry 2280A Lecture Notes - Lecture 2: Deprotonation, Amine, Ph1B

• School: Western University
• Department: Biochemistry
• Course: Biochemistry 2280A
• Professor: Boffa/ Mc Lauchlin/ Brandl

Document Summary

Topic 2: amino acids and the peptide bond. Be able to calculate ph and pka values. Be able to calculate the charge on amino acid groups. Many groups in an aa are ionizable (become charged) The ionization state of these groups critically influences a protein"s structure and function. Ph (i. e. the number of protons available in solution) h+ concentration. Affinity of the ionizable group for its proton (pka) If protons on side chains are lost, they may go from non-polar polar charged or polar. When we classify aas, it is done under ph=7 conditions. Describes the strength of weak acids and bases. Aa contains weak acidic and basic groups that ionize when placed in water. Fraction of ionized molecules (rcoo-) decreases with increasing ph: acidic: rcooh rcoo- + h+ + rnh2 + h+ (decreasing h+: basic: rnh3. Quantitative measure of the strength of an acid; personal scale of acidity. Pka = ka = strength acid = affinity for h+