Problem Title: Isoelectric Point and Electrophoresis (Intro to Biochemistry) The

Question

Problem Title: Isoelectric Point and Electrophoresis (Intro to Biochemistry)

The isoelectric point, pI, of the protein pepsin is 1 , while that of alkaline phosphatase is 4.5 .

What is the net charge of pepsin at pH 5.1 ?_________ (Choose: positive or negative)
What is the net charge of alkaline phosphatase at pH 2.1 ?_________ (Choose: positive or negative)

The isoelectric point of histidine is 7.59 ; threonine , 5.6 .

During paper electrophoresis at pH 7.1 , toward which electrode does histidine migrate? _________ (Choose: positive or negative)
During paper electrophoresis at pH 4.5 , toward which electrode does threonine migrate? _________ (Choose: positive or negative)

Explanation / Answer

the net charge of pepsin at pH 5.1 is negative ( as pH > pI )

the net charge of alkaline phosphatase at pH 2.1 ____POSITIVE CHARGE ( as pH< pI)

paper electrophoresis at pH 7.1 , toward which electrode does histidine migrate negative electrode.( as the net charge is positive and it should move towards negative electrode)

During paper electrophoresis at pH 4.5 , toward which electrode does threonine migrate negative electrode. ( even the net charge on threonine is positive so it migrates towards negative)

i hope im clear. comment if you have any doubt. all the best

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