High Yield MCAT: Amino Acids Overview

Key Concepts

• Amino Acids & Residues: In biological contexts, amino acids are sometimes referred to as residues.
• Proteinogenic Amino Acids: There are more than 20 amino acids, but only 20 are encoded by the human genome, termed proteinogenic amino acids.
  • Etymology: "Proteinogenic" means protein-producing.

Genetic Encoding

• Start Codon:
  • AUG: The only mRNA codon you need to memorize for the MCAT, encoding Methionine.

Methionine

• Abbreviations:
  • Three-letter: Met
  • One-letter: M
• Structure:
  • Backbone with a unique R group with sulfur.
• Classification:
  • Nonpolar
• pKRs: Not applicable for Methionine as it doesn’t readily accept/donate hydrogens.
• Special Characteristics:
  • Encoded by the start codon AUG.

Important Concepts for Studying

• Memorization: Flashcards are recommended.
  • Apps: Anki (preferred for medical students), Quizlet.
  • Technique: Draw structures by hand to aid memorization.

Fundamental Characteristics of Amino Acids

• Basic Structure:
  • Includes a hydrogen attached to the middle carbon (alpha carbon) in the backbone.
• Zwitterionic Nature:
  • Amino acids have both a positive and negative charge, making the net charge zero at physiological pH (7.4).
• N-Terminus & C-Terminus:
  • Ends of a polypeptide; terminology arises from amino and carboxylic acid groups.
• R Group:
  • Distinguishes each amino acid.
  • Not an actual atom but a functional group.
• Alpha Carbon (Cα):
  • One carbon away from the carbonyl carbon; only one per amino acid.
  • Chiral center in eukaryotic amino acids (L-configuration).

Conclusion

• This session provided an introduction to amino acids, focusing on their genetic encoding, structure, and classification as it relates to MCAT.
• Encouragement to utilize resources like flashcards and visualization for effective study.