Amino Acid Pool Regulation

Amino Pool and Nitrogen Metabolism

• Amino pool, approximately 90-100 g, is essential for nitrogen metabolism despite being small compared to total body protein (about 12 kg in a 70-kg male).
• Depleted by:
  • Synthesis of body proteins
  • Usage as precursors for nitrogen-containing molecules
  • Conversion to glucose, glycogen, fatty acids, ketone bodies, or CO2 + H2O.

Protein Turnover

• Most body proteins undergo constant synthesis and degradation to manage abnormal proteins.
• Regulation of synthesis primarily controls protein concentration; however, some proteins are maintained by selective degradation.

Plasma Proteins

• Plasma proteins, primarily synthesized by the liver, play diverse roles.
• Key plasma proteins:
  • Albumin: 60% of blood proteins; maintains blood osmotic pressure and electrolyte balance.
  • Globulins: Includes alpha, beta, and gamma globulins with various functions such as immune response and transport.
    • Alpha globulins: Includes alpha-fetoprotein for cancer markers.
    • Beta globulins: Includes transferrin and complement proteins.
    • Gamma globulins: Known as immunoglobulins, crucial for immunity.
  • Fibrinogen: Essential for blood clot formation, converted to fibrin during clotting.

Functions of Plasma Proteins

• Maintains blood osmotic pressure via albumin.
• Globulins and albumin transport hormones, enzymes, and molecules.
• Fibrinogen plays a primary role in blood clot formation.
• Some globulins, including immunoglobulins, are vital for immune function.

Hormonal Regulation of Protein Metabolism

• Proteins undergo catabolism to replenish the intracellular amino acid pool.
• In starvation, muscle protein breakdown provides amino acids for gluconeogenesis, serving as an energy source.
• Excess amino acids can be converted to glucose, ketones, or decomposed, producing nitrogenous waste that is processed through the urea cycle.

Functions and Importance of Vitamins

• There are 13 essential vitamins necessary for human health, divided into water-soluble and fat-soluble categories.
• Vitamins cannot usually be synthesized by the body in sufficient amounts and must be obtained through diet or supplements.

Water-Soluble Vitamins

• Vitamin B1 (Thiamine): Vital for carbohydrate metabolism and nerve function; deficiency leads to nerve impairment.
• Vitamin B2 (Riboflavin): Assists in energy production and lipid metabolism; deficiency causes skin and ocular issues.
• Vitamin B3 (Niacin): Important for metabolism and digestion; deficiency causes skin lesions and gastrointestinal issues.
• Vitamin B6: Key for amino acid metabolism and synthesis of hemoglobin; deficiency results in depression and anemia.
• Folic Acid (B9): Crucial for DNA synthesis and red blood cell maturation; deficiency leads to weakness and developmental issues in fetuses.
• Vitamin B12: Necessary for amino acid and fatty acid metabolism; deficiency causes gastrointestinal and nervous problems.
• Pantothenic Acid: Essential for carbohydrate, protein, and fat metabolism; deficiency includes weakness and sleep disturbances.
• Biotin: A cofactor in various metabolic processes; deficiency can cause dermatitis and hair loss.
• Vitamin C: Acts as an antioxidant and is vital for collagen synthesis and immune function; deficiency leads to poor wound healing and gum issues.

Fat-Soluble Vitamins

• Vitamin A: Essential for vision, skin health, growth, and immune response; deficiency can cause blindness and infection vulnerability.
• Vitamin D: Maintains calcium and phosphorus levels, supporting bone health; deficiency leads to improper bone growth.
• Vitamin E: Functions as an antioxidant and protects cell membranes; deficiency may result in peripheral neuropathy.
• Vitamin K: Important for blood coagulation and bone metabolism; deficiency causes impaired clotting.

Vitamin Supplementation Trends

• Vitamin A supplement market projected to exceed $860 million by 2024.
• B Vitamins are popular and often taken as a complex for synergistic effects.
• Vitamin C is a widely consumed supplement, with the market expected to generate approximately $9.8 billion by 2022.
• Vitamin D supplements, crucial for aging populations, are projected to reach $2.5 billion in sales.

Learn about the processes that deplete the amino acid pool in the body, including protein synthesis and the conversion of amino acids to glucose and other molecules.