Video: EC17-18-S2-Q13

What type of acid is glycine? (a) Hydroxylic acid (b) Amino acid (c) Aromatic acid (d) Fatty acid

02:15

Video Transcript

What type of acid is glycine? a) Hydroxylic acid, b) amino acid, c) aromatic acid, or d) fatty acid.

To kick off this question, we’re going to recall the structure of glycine. This is the structure of glycine. It has an amine group and a carboxylic acid group. What we’re going to do is compare the structure of glycine with the general formulas of the types of acid listed to see which one it corresponds to. Hydroxylic acid is not a type of acid at all. It is in fact another name for water. This is therefore not a correct answer.

One definition of amino acid is a simple organic compound containing an amine group and a carboxylic acid group. However, the term amino acid is more commonly used for organic compounds with this general formula. As we can see from the structure, the R group for glycine is H. So glycine fulfils the definition of amino acid and fits in the general formula of the most common amino acids. Therefore, amino acid is the correct answer.

Just to be safe, let’s have a look at aromatic acid. An example of an aromatic acid would be benzoic acid. Glycine is fully aliphatic. It does not contain any aromatic rings. Therefore, it cannot be an aromatic acid. Therefore, this is an incorrect answer. And lastly, fatty acids. Fatty acids, like palmitic acid, have a carboxylic acid head and a long aliphatic tail. Glycine, being a small, organic molecule, does not have a long aliphatic tail. Therefore, glycine is not a fatty acid.

So, of the types of acid given, glycine is most certainly an amino acid.

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