Serine exists in its zwitterion form at a pH of 5.7. Draw the structural formula for the same. Explain the manner in which the structural formula of polar and non-polar amino acids would vary
To draw the structural formula of serine in its zwitterion form at a pH of 5.7, we first need to understand what a zwitterion is. A zwitterion is a molecule that has both positive and negative charges within the same molecule. In the case of serine, the zwitterion form is a result of its amino group (NH2) acting as a base and accepting a hydrogen ion (H+) from its carboxyl group (COOH) when the pH is below its pKa value.
Now, let's draw the structural formula of serine in its zwitterion form:
H
|
H3N⁺─C─COO⁻
|
CH2
|
OH
In this structural formula, the amino group (NH2) has accepted an additional hydrogen ion (H+) to become NH3⁺, giving it a positive charge. Meanwhile, the carboxyl group (COOH) has lost a hydrogen ion (H+) to become COO⁻, giving it a negative charge. The central carbon is connected to a hydrogen atom (H), a methylene group (CH2), and a hydroxyl group (OH).
Now, let's discuss the differences in the structural formulas of polar and non-polar amino acids:
Polar amino acids have functional groups that can form hydrogen bonds or interact with water molecules due to their partial charges. These functional groups usually include hydroxyl (OH), amino (NH2), carboxyl (COOH), or sulfhydryl (SH) groups. These functional groups make the molecule more hydrophilic, meaning they have an affinity for water. Examples of polar amino acids include serine, threonine, and asparagine.
Non-polar amino acids, on the other hand, lack charged or polar functional groups. They are primarily composed of hydrocarbon chains and are therefore more hydrophobic, meaning they have low affinity for water. Examples of non-polar amino acids include glycine, alanine, and leucine.
The structural formulas of polar amino acids often have additional functional groups attached to the central carbon, resulting in more complex structures. In contrast, the structural formulas of non-polar amino acids usually consist of simpler hydrocarbon chains without additional functional groups.
Understanding the differences in the structures of polar and non-polar amino acids helps in determining their properties, behavior, and interactions within biological systems.