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.