Question 7 of 32beginner🔧 ApplyDiagram2 marks

Draw the structure of the amino acid, alanine.

Correct Answer

The structure of alanine can be represented as follows:

At neutral pH (Zwitterionic form):

H₃N⁺
   |
H—C—CH₃
   |
 COO⁻

Alanine is a neutral amino acid where the R group is a methyl group (–CH₃). The structure consists of an amino group (–NH₂), a carboxyl group (–COOH), a hydrogen atom, and the R group (methyl) attached to the same carbon atom (alpha carbon). Due to the ionizable nature of –NH₂ and –COOH groups, amino acids exist in different forms at different pH values. At neutral pH, alanine exists predominantly in the zwitterionic form where the amino group is protonated (–NH₃⁺) and the carboxyl group is deprotonated (–COO⁻).

Exercise: EXERCISES | Q: 7 | (Page 16)
For More Understanding

Explanation

According to the textbook context, alanine has a methyl group as its R group. The context states: 'The R group in these proteinaceous amino acids could be a hydrogen (the amino acid is called glycine), a methyl group (alanine)'. The general structure of amino acids shows the amino and carboxyl groups attached to the same carbon along with R group and hydrogen. The context also explains that amino acids have ionizable –NH₂ and –COOH groups, and they exist in zwitterionic form at certain pH values.

Solution Steps

  1. Step 1: Identify that alanine has a methyl group (–CH₃) as its R group from the context.

  2. Step 2: Draw the general amino acid structure with amino group, carboxyl group, hydrogen, and R group attached to the alpha carbon.

  3. Step 3: Replace the R group with methyl group (–CH₃) to get alanine structure.

PreviousNext