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Essential Amino Acids for MCAT Success

May 20, 2025

Biochemistry: Amino Acids Chart

Importance for MCAT

  • Memorize structures, names, three-letter and one-letter abbreviations of amino acids.
  • Abbreviations could appear in questions and passages.
  • Use mnemonics to remember types of amino acids and their abbreviations.

Concept Check

  • "ILYSM": Understanding letter nomenclature of amino acids is crucial.

MCAT Content Connections

Biology, Gene Expression

  • Amino Acid Substitution Example:
    • F42Y: Phenylalanine (F) at position 42 replaced by Tyrosine (Y).
    • Caused by genetic mutations, e.g., single nucleotide change.
    • Mutation from phenylalanine codons (UUU/UUC) to tyrosine (UAU/UAC).
    • Impact on protein:
      • Altered folding, interaction, or stability.
      • New chemical properties due to changes, e.g., hydroxyl group on tyrosine for hydrogen bonding.

Classification Based on the Polarity of the Side Chain

Polarity of Molecules

  • Definition: Distribution of electric charge around a molecule.
  • Types:
    • Polar Molecules: Uneven electron distribution due to differing electronegativities (difference of 0.5 or more).
    • Nonpolar Molecules: Even electron distribution with similar electronegativities.
  • Electronegativity: Ability of an atom to attract electrons, influencing polarity.

Factors Determining Polarity

  • Covalent Bonds:
    • Electrons shared between atoms.
    • Even distribution = Nonpolar.
    • Uneven distribution = Polar, with regions of slight negative and positive charges.