Correct Answer: Isoelectric point (pI) is the pH where protein has no net charge.
Step 1: Understand that proteins are made of amino acids, which can have positive, negative, or neutral charges depending on the pH of their environment.
Step 2: Know that pH is a measure of how acidic or basic a solution is, with lower values being more acidic and higher values being more basic.
Step 3: Realize that at different pH levels, the charges on the amino acids in a protein can change.
Step 4: Identify the isoelectric point (pI) as the specific pH where the total charge of the protein is zero, meaning it has no net charge.
Step 5: Understand that at the isoelectric point, the protein is least soluble in water, which can affect its behavior in biological systems.
