Intermediate Topic 826 of 1102 Organic Chemistry
Amino Acids
Molecules with amine and carboxyl groups, the building blocks of proteins.
In-depth explanation of Amino Acids
Amino acids contain an amino group and a carboxyl group bonded to the same alpha carbon, along with a side chain R that defines each of the twenty standard types. Except for glycine, whose side chain is hydrogen, the alpha carbon is a stereocentre, and nearly all natural amino acids have the L configuration. Amino acids are amphoteric, meaning they can act as both acids and bases. They join together through peptide bonds to form proteins, and their side chains determine how the protein folds and functions.
Going deeper: Amino Acids
Key ideas: Alpha amino acids, H2N-CHR-COOH, number 20 standard in proteins; all natural ones are L (S configuration, except cysteine which is R) and glycine is achiral. Classified as nonpolar, polar neutral, acidic (Asp, Glu) or basic (Lys, Arg, His). Typical pKa values: COOH about 2, NH3+ about 9. Essential amino acids must come from the diet (about 9 for adults).
Common mistakes and connections: Students claim all L amino acids are S; cysteine is R because sulfur outranks the other substituents. Another error is drawing the neutral amino acid form for dissolved samples at pH 7, where the zwitterion exists. Links to zwitterions, peptide bonds, protein structure and Strecker synthesis.
Visualization of Amino Acids
Glycine, the simplest amino acid, has NH2 and COOH groups on one alpha carbon; other amino acids add a side chain there. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Glycine is the only one of the twenty standard amino acids that is achiral, because its side chain is a hydrogen atom.
Frequently asked questions about Amino Acids
What is Amino Acids?
Molecules with amine and carboxyl groups, the building blocks of proteins.
Is Amino Acids a beginner, intermediate or advanced topic?
Amino Acids is a intermediate topic in Organic Chemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Amino Acids?
Study these earlier topics in Organic Chemistry first: Carbohydrate Structure, Glucose Ring Forms, Reducing Sugars.
What comes after Amino Acids?
The next topics in Organic Chemistry are Zwitterions and Peptide Bond.
Can I practise Amino Acids with quizzes?
Yes. The interactive lesson includes a self-check question on Amino Acids, and the Organic Chemistry quiz draws on every topic in this area.
Where Amino Acids fits in Organic Chemistry
Amino Acids is topic 98 of 148 in Organic Chemistry.