Lecture Notes on Amino Acids

Overview

• There are 20 amino acids to recognize in medical school.
• Important as building blocks of protein and metabolic intermediates.
• Categories to focus on:
  • Essential vs. Non-essential
  • Acidic vs. Basic
  • Ketogenic, Glucogenic, and Mixed
  • Branched Chain Amino Acids

Essential vs. Non-Essential Amino Acids

• Essential Amino Acids: Cannot be produced by the body; must be obtained through the diet.
  • Examples: Threonine, Tyrosine, Valine, Phenylalanine, Isoleucine, Leucine, Lysine, Methionine, Histidine
• Non-Essential Amino Acids: Can be produced by the body; not necessary in the diet.

Acidic vs. Basic Amino Acids

• Acidic Amino Acids:
  • Aspartic Acid
  • Glutamic Acid
• Basic Amino Acids:
  • Histidine, Lysine, Arginine
  • Mnemonic: "Her Leggings Are Basic" (HLA)

Ketogenic, Glucogenic, and Mixed Amino Acids

• Ketogenic Amino Acids: Leucine, Lysine
• Glucogenic Amino Acids: Histidine, Methionine, Valine
• Mixed Amino Acids: Isoleucine, Threonine, Tyrosine, Phenylalanine
• Mnemonics:
  • Ketogenic Diet: Lamb and Liver (Leucine and Lysine)
  • Glucogenic Diet: Honey, Mango, Vanilla (Histidine, Methionine, Valine)

Amino Acid Derivatives

• Phenylalanine → Tyrosine → DOPA → Dopamine → Norepinephrine → Epinephrine (Catecholamines)
• Tryptophan:
  • Derivatives: Niacin (NAD+, NADP+) and Serotonin (Melatonin)
  • Co-factors: Vitamin B2, Vitamin B6, BH4
  • Related Disease: Hartnup Disease (Decreased resorption of tryptophan)
    • Symptoms: Pellagra (Diarrhea, Dementia, Dermatitis)
    • Treatment: Nicotinic acid
• Histidine → Histamine (Vitamin B6)
• Glycine → Porphyrin → Heme (Vitamin B6)
• Glutamate → GABA or Glutathione (Vitamin B6)
• Arginine → Creatine, Urea, Nitric Oxide (Complex)

Branched Chain Amino Acids (BCAAs)

• Amino Acids: Isoleucine, Leucine, Valine
• Enzyme: Branched Chain Alpha-Keto Acid Dehydrogenase
• Disease: Maple Syrup Urine Disease (Due to enzyme deficiency)
  • Symptoms: Syrup-smelling urine, Intellectual disability, Poor oral intake
  • Mnemonic: "I love Vermont maple syrup. Can I have a sip?"
    • I: Isoleucine
    • L: Leucine
    • V: Valine
    • S: Syrup smell
    • I: Intellectual disability
    • P: Poor oral intake

Summary

• Understand the categories: Essential vs. Non-essential, Acidic vs. Basic, Ketogenic, Glucogenic, or Mixed, and Branched.
• Know high yield derivatives, especially Tryptophan and the implications of Hartnup Disease.
• Be aware of Maple Syrup Urine Disease related to BCAAs.

---

Note: Review these key points regularly to prepare for exams.