Mnemonic Strategies for Amino Acids

Mar 13, 2025

Understanding Amino Acids and Their Side Chains

Overview

  • Amino acids are composed of:
    • Alpha carbon
    • Hydrogen
    • Carboxy group
    • Amine
    • Variable side chain (R group)
  • This lecture focuses on memory tricks to remember the 20 common amino acids and their side chains.

Non-polar Amino Acids

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  • Glycine (Gly, G):
    • No R-group, just a hydrogen
    • Achiral
    • Neither hydrophobic nor hydrophilic
  • Alanine (Ala, A):
    • Smallest side chain, CH3
    • Aliphatic and hydrophobic
  • Valine (Val, V):
    • Isopropyl group (upside down V)
    • Aliphatic and hydrophobic
  • Leucine (Leu, L):
    • Isobutyl side chain
    • Aliphatic and hydrophobic
  • Isoleucine (Ile, I):
    • Sec butyl group, isomer of Leucine
    • Aliphatic and hydrophobic with a second chiral center
  • Methionine (Met, M):
    • Sideways M with sulfur
    • Aliphatic and hydrophobic
  • Phenylalanine (Phe, F):
    • Benzyl group (phenyl on alanine)
    • Aromatic and hydrophobic
  • Tryptophan (Trp, W):
    • Bicyclo ring (5-member and 6-member rings)
    • Aromatic and hydrophobic
  • Proline (Pro, P):
    • Involves the amine group, swings around
    • Hydrophobic

Polar Amino Acids

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  • Serine (Ser, S):
    • Simple alcohol (add OH)
    • Polar and hydrophilic
  • Threonine (Thr, T):
    • Three groups (methyl, OH)
    • Polar and hydrophilic
  • Tyrosine (Tyr, Y):
    • Tire (benzene ring) with OH
    • Borderline hydrophobic, aromatic
  • Cysteine (Cys, C):
    • C and S with SH
    • Hydrophobic, can form disulfide bridges
  • Asparagine (Asn, N):
    • CH2 + amide
    • Polar and hydrophilic
  • Glutamine (Gln, Q):
    • Two CH2 + amide
    • Polar and hydrophilic

Acidic Amino Acids

  • Aspartic Acid (Asp, D):
    • CH2 + carboxylic acid
    • Negative carboxylate at physiological pH
  • Glutamic Acid (Glu, E):
    • Two CH2 + carboxylic acid
    • Negative carboxylate at physiological pH

Basic Amino Acids

  • Lysine (Lys, K):
    • Four carbons + basic nitrogen
    • Fully protonated at physiological pH
  • Arginine (Arg, R):
    • Guanidinium group
    • Positive charge on nitrogen
  • Histidine (His, H):
    • Five-member ring
    • Basic nitrogen with positive charge

Resources

Full transcript