Question

A pH gradient is formed during isoelectric focusing. Which of the following describes how protein molecules distribute themselves during isoelectric focusing?

More than one option is correct.

Question 5 options:

	proteins migrate towards the positive electrode at positive pH.
	proteins migrate in an electric field based on their net charge.
	proteins cease migration when they have an equal number of positive and negative charges at the ambient pH.
	proteins migrate in an electric field until pH extremes denature their secondary structure.
	the isoelectric point of a protein reflects its amino acid composition.

Answer 1

Answer-

1. Protein migrates in an electric field based on their net charge.

2. Protein cease migration when they have an equal number of positive and negative charges at the ambient pH.

3. The isoelectric point of a protein reflects its amino acid composition.

Explanation-

1. Protein migrates in an electric field based on their net charge-

Protein has charge based on their amino acid content. When electric field is provided in isoelectric focusing, protein moves towards cathode or anode depending on net charge. At low pH most proteins has positive charge and protein moves towards cathode and at high pH protein has negative charge so move towards anode. Protein moves in electric field untill their net charge will become 0 in pH gradient.

2. Protein cease migration when they have an equal number of positive and negative charges at the ambient pH-

When protein has equal number of positive and negative charges then net charge will be 0 and pH at which protein has net 0 charge is known as isoelectric pH or isoelectric point. So that protein cease migration at isoelectric pH because protein doesn't have net positive or negative charge.

3. The isoelectric point of a protein reflects its amino acid composition-

By isoelectric focusing technique proteins can be separated using their different isoelectric points. This isoelectric point reflects relative content of acidic and basic amino acid residues in proteins.