Final answer:
Most proteins have an isoelectric point below pH 7. This point is when proteins carry no net charge, becoming least soluble and often precipitating out of solution.
Step-by-step explanation:
The question pertains to the isoelectric point of proteins, which is the pH at which a protein has an equal number of positive and negative charges and therefore carries no net charge. When proteins are at this pH, they do not move in an electric field, and they become least soluble, potentially precipitating out of solution.
For most proteins, the isoelectric point tends to be below pH 7. This is because the side chains of many amino acids that make up proteins can become protonated or deprotonated, affecting the protein's overall charge. Therefore, the correct answer is C) below.
Examples include casein, which has an isoelectric point of 4.5. At this pH, casein curdles in milk. Basic amino acids have higher isoelectric points, while acidic amino acids have lower isoelectric points.
The isoelectric point (pI) of a protein refers to the pH at which the protein carries no net charge and exists in its zwitterion form, where the positive and negative charges balance out. Most proteins have an isoelectric point below 7, indicating that they are more acidic in nature. This means that at a pH below 7, the proteins will have a positive charge and at a pH above 7, they will have a negative charge.