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 pH 5.7, we need to understand the properties of serine and how it behaves under different pH levels.
Serine is an amino acid with the chemical formula C3H7NO3. It contains a central carbon atom (C) bonded to an amino group (NH2), a carboxyl group (COOH), a hydrogen atom (H), and a side chain that includes a hydroxyl group (OH).
At pH 5.7, serine exists in its zwitterion form. A zwitterion is a molecule that contains both a positive and a negative charge, making it electrically neutral overall. In the case of serine, the carboxyl group will be negatively charged (COO-) and the amino group will be positively charged (NH3+).
To draw the structural formula of serine in its zwitterion form at pH 5.7:
1. Start with the central carbon atom (C).
2. Attach the amino group (NH2) to one side of the carbon atom.
3. Attach the carboxyl group (COOH) to the other side of the carbon atom.
4. Attach a hydrogen atom (H) to the carbon atom.
5. Add the side chain, which contains the hydroxyl group (OH), to the carbon atom.
The structural formula of serine in its zwitterion form at pH 5.7 should look like this:
H
|
NH2
|
C
/ \
OH COO-
Now, let's discuss how the structural formulas of polar and non-polar amino acids may vary.
Amino acids can be classified as polar or non-polar based on the characteristics of their side chains.
Non-polar amino acids have side chains that consist mainly of hydrocarbon groups, such as methyl or ethyl groups (e.g., alanine, valine, leucine). In their structural formulas, the side chains of non-polar amino acids are usually represented as simple hydrocarbon chains or rings without any electronegative atoms.
Polar amino acids, on the other hand, have side chains that contain electronegative functional groups, such as hydroxyl groups (e.g., serine, threonine) or amine groups (e.g., asparagine, glutamine). These functional groups can form hydrogen bonds or interact with water molecules due to their partial charges. In the structural formulas of polar amino acids, the side chains will include these functional groups, which contribute to their polar nature.
In summary, the structural formulas of polar amino acids like serine will have side chains containing electronegative functional groups, while non-polar amino acids will have side chains consisting mainly of hydrocarbon groups.