/20/2018 11:00 PMASS PrintCalculatorPeriodic Table stion 19 of 27 Ma Sapling Lea

Question

/20/2018 11:00 PMASS PrintCalculatorPeriodic Table stion 19 of 27 Ma Sapling Learning All amino acids have two ionizable functional groups: an a-amino group (average pKe of 9.4) and an a-carboxylic acid group (average pk, of 2.2). Tyrosine also has an ionizable side chain (R group) with a pk, of -10.1.One of the possible ionization states of tyrosine is shown below 0 H3N-CH-C-OH CH2 At what pH would the structure above be the predominant ionization state? Note: Consider the ionization state of ali three of the functionai groups. pHSelect answer Scroll down for more of this question. The protonated form of the R group of tyrosine is shown in the structure above. The ratio of the protonated form to the charged (deprotonated) form depends on the pk, of the R group and the pH Prevous @jive up & View Scadon 9 Check Answer Next Exit Hint about us careers prvacy policy terms of use contact us F3 ODO F4 F5 F6 F8

Explanation / Answer

Q1. pH = 1.0

Q2. Correct option is 12.0

Explanation

Q1. The given form of Tyrosine is fully protonated which means there is excess of protons (or H+) and hence pH is very low (lower than pKa of carboxylic acid group). Hence pH is lower than 2.2. I have selected pH = 1.0 but you can also select any pH which is lower than 2.2

Q2. The unprotonated form of side chain will predominate when pH greater than pKa of side chain which is 10.1

Hence correct option is 12.0 because 12.0 is greater than 10.1

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