Amino Acids and Their Roles

Essential and Nonessential Amino Acids

• Amino Acid Classification

  • Essential Amino Acids: Cannot be synthesized by the body; must be obtained from diet.
  • Nonessential Amino Acids: Can be synthesized by the body; do not need to be obtained from diet.

• Examples of Aromatic Amino Acids

  • **Essential Amino Acids: **
  • Alanine
  • Tryptophan
  • Nonessential Amino Acids:
  • Arginine (conditionally essential)
    • Exception: Body synthesizes arginine, but not in sufficient amounts for needs, especially during growth.
  • Tyrosine
    • Derived from phenylalanine, requires dietary precursor for its synthesis.

Regulation of Amino Acid Production

• Short-Term Regulation

  • Allosteric Regulation:
  • Feedback inhibition of amino acid production is regulated by the concentration of amino acids.
  • e.g., Threonine inhibits its own synthesis from homoserine.

• Metabolic Pathways

  • Some amino acids require numerous chemical steps for synthesis, e.g.:
  • Methionine and histidine are complex and not easily synthesized, making them essential.
  • Common Precursor Molecules:
  • Nonessential amino acids often share similar carbon backbones with central metabolic intermediates like pyruvate and oxaloacetate.

Cultural Aspects and Dietary Considerations

• Cultural Dietary Examples:

  • Red Beans & Rice: Provides complete proteins when combined; prevalent in certain cultures for health benefits.
  • Succotash: Traditional Native American dish; highlights cultural importance of combining protein sources.

• Plant-Based Protein Sources:

  • Careful dietary balance needed for complete proteins, especially in vegetarian and vegan diets.

Chikismate Pathway and Genetic Engineering

• Chikismate Pathway:

  • Plants synthesize aromatic amino acids via this pathway; requires specific enzymes.
  • EPSP synthase is crucial for converting shikimate-3-phosphate to chorismate.

• Glyphosate and GMOs:

  • Glyphosate is a herbicide that inhibits EPSP synthase, affecting plant growth.
  • Genetically modified organisms (GMOs) have been engineered to carry a resistant variant of the EPSP synthase enzyme, allowing them to withstand glyphosate application.
  • Concerns about environmental and health impacts regarding glyphosate leakages into water sources.

General Takeaways

• Essential vs. Nonessential: Understanding the classification of amino acids is key to nutrition and biology; knowing dietary sources and metabolic pathways is critical.
• Regulatory Mechanisms: The body has evolved mechanisms to efficiently regulate amino acid levels based on dietary intake and metabolic needs.
• Cultural Impact: Dietary practices often reflect biochemical principles, emphasizing the relationship between biochemistry and culture, particularly in protein consumption habits.