Question

Isoelectric point of Alanine is 6 . At which pH maximum concentration of zwitter ion of alanine will be present? (A) \(\mathrm{pH}>6\) (B) \(\mathrm{pH}<6\) (C) \(\mathrm{pH}=6\) (D) \(\mathrm{pH}=7\)

Short answer

The maximum concentration of zwitterion of alanine will be present at its isoelectric point. Therefore, the correct option is (C) \(\mathrm{pH}=6\).

Step-by-step solution

Recall the Isoelectric Point Definition

Remember that the isoelectric point (pI) is the pH value at which the amino acid exists mainly in its zwitterionic form. Hence, the maximum concentration of zwitterion will be present at the pI.

Compare the Given pI to the pH Options

We are given that the pI of alanine is 6. Now, we need to compare this pI to the pH options provided: (A) \(\mathrm{pH}>6\) (B) \(\mathrm{pH}<6\) (C) \(\mathrm{pH}=6\) (D) \(\mathrm{pH}=7\)

Choose the Correct Option

The maximum concentration of zwitterion of alanine will be present at its isoelectric point, which is 6. So, the correct option is: (C) \(\mathrm{pH}=6\)

Key concepts

Zwitter Ionic Form

The term "zwitter ionic form" might sound complicated, but it actually refers to a specific type of molecule known as a zwitterion. Zwitterions are special because they have both positive and negative charges, but the overall molecule is neutral. This unique feature allows them to act in interesting ways in different environments. For amino acids, this zwitterionic state is particularly important.

Amino acids, which are the building blocks of proteins, can exist in this zwitterionic form at certain pH levels. At a specific pH, known as the isoelectric point (pI), amino acids like alanine exhibit both a negatively charged carboxylate group (-COO-) and a positively charged ammonium group (-NH3+). These charges balance each other out, resulting in a neutral molecule. At the pI, the concentration of the zwitterion is at its maximum.

This property of amino acids makes them versatile in different biochemical processes, as they can interact with other charged molecules and ions more efficiently when they are in their zwitterionic form.

Amino Acids

Amino acids are the basic units that make up proteins. Imagine them as the Lego pieces that, when combined, build the intricate structures that are proteins. Each amino acid consists of a central carbon atom bonded to four groups:

• A hydrogen atom (H)
• An amino group (-NH2)
• A carboxyl group (-COOH)
• A unique side chain (R group)

These components give amino acids unique properties, and the side chain, in particular, determines the characteristics and behavior of each amino acid.

The environment around an amino acid, especially the pH, influences its state. For instance, in acidic conditions (low pH), amino acids tend to gain protons, whereas, in basic conditions (high pH), they can lose protons. This ability to switch forms helps them function as buffers, maintaining stability in various biological systems. Understanding how amino acids behave at different pH levels is crucial in fields like biochemistry and medicine.

pH Value

The concept of pH is fundamental in chemistry, especially when studying biological molecules like amino acids. pH is a scale used to determine how acidic or basic a solution is. It ranges from 0 to 14, with 7 being neutral (like pure water).

• A pH below 7 indicates an acidic solution.
• A pH above 7 indicates a basic or alkaline solution.

For amino acids, pH is particularly important because it determines their charge state. Surprising as it may seem, this scale dictates whether an amino acid will exist in its cationic form, anionic form, or as a zwitterion.

At their isoelectric point (pI), amino acids are in the zwitter ionic form. They have no net charge, making them unique in their interactions. For alanine, this pI is at pH 6, which is why at this pH level, alanine is mostly present as a zwitterion. The pH value not only influences how molecules are charged but also affects biochemical reactions and processes, highlighting its importance in many scientific disciplines.