Chemical Digestion Overview

Carbohydrates

• Forms: Monosaccharides (e.g., Glucose), Disaccharides (e.g., Sucrose, Maltose), Polysaccharides (e.g., Starch, Cellulose)
• Digestion Locations:
  • Oral cavity: Salivary amylase starts breaking down starch
  • Small intestine: Pancreatic amylase continues breakdown, brush border enzymes complete digestion
• Enzymes:
  • Salivary amylase (oral cavity)
  • Pancreatic amylase (small intestine)
  • Brush border enzymes: lactase, maltase, sucrase
• Absorption:
  • Monosaccharides absorbed and converted to glucose in liver
  • Glucose is used for energy or stored as glycogen or fat
• Cellulose: Not digestible, adds fiber, aids in bowel movement

Proteins

• Structure: Made of amino acids linked by peptide bonds
• Digestion Locations:
  • Stomach: Pepsinogen converted to pepsin in low pH
  • Small intestine: Trypsinogen, chymotrypsinogen, and procarboxypeptidase activated
• Enzymes:
  • Pepsin (stomach)
  • Trypsin, chymotrypsin, carboxypeptidase (small intestine)
  • Brush border enzymes: Aminopeptidase, dipeptidase
• Absorption:
  • Amino acids absorbed and used for protein synthesis or converted to glucose

Lipids

• Types: Triglycerides (fats), cholesterol
• Digestion Locations:
  • Mouth: Lingual lipase
  • Stomach: Gastric lipase
  • Small intestine: Pancreatic lipase
• Process:
  • Emulsification by bile salts
  • Pancreatic lipase breaks down into monoglycerides and fatty acids
• Absorption:
  • Enter lacteals and then bloodstream

Celiac Disease

• Autoimmune response to gluten damaging villi
• Results in poor nutrient absorption

Water, Electrolytes, and Vitamins

• Water: Mostly absorbed in small intestine
• Electrolytes: Absorption dependent on diet, iron absorption is regulated
• Vitamins:
  • Fat-soluble (A, D, E, K): Absorbed with lipids
  • Water-soluble (B, C): Absorbed via diffusion/active transport
  • B12 requires intrinsic factor for absorption

Conclusion: This marks the end of the digestive system module. Next is the urinary system.