IGCSE Study Buddy: Human Nutrition Part 2

Overview

• Focus on chemical digestion within human nutrition
• Breaks down large insoluble molecules into small soluble molecules
• Aim: produce molecules that can be absorbed by the body

Chemical Digestion

• Role: Convert food into absorbable molecules

Enzymes in Digestion

• Amylase:
  • Breaks down starch to maltose; maltase further breaks down maltose to glucose
  • Acts in the mouth and duodenum
• Protease:
  • Breaks down proteins to amino acids
  • Pepsin (stomach, acidic environment) and Trypsin (small intestine, alkaline environment)
• Lipase:
  • Breaks down fats and oils into fatty acids and glycerol
  • Acts in the duodenum

Enzyme Activity Locations

• Amylase:
  • Secreted by salivary glands and pancreas
  • Acts in mouth and duodenum
• Protease Pepsin:
  • Produced and acts in the stomach
• Protease Trypsin:
  • Secreted by pancreas, acts in duodenum
• Lipase:
  • Secreted by pancreas, acts in duodenum

Hydrochloric Acid in Gastric Juice

• Functions:
  • Kills harmful microorganisms
  • Provides acidic pH for enzyme activity
  • Enables pepsin to work optimally in the stomach

Bile's Role in Digestion

• Functions:
  • Emulsifies fats (physical digestion)
  • Neutralizes acidic mixture from the stomach
  • Provides suitable alkaline pH for enzyme action in small intestine

Absorption

• Definition: Movement of digested food molecules into the blood
• Location: Small intestine, primarily in the ileum
• Most water absorbed in small intestine, some in colon

Ileum Adaptations for Absorption

• Highly folded surface with villi and microvilli
• Increases surface area for efficient absorption

Structure of a Villus

• Villi:
  • Finger-like projections
  • Capillaries: Absorb glucose, amino acids, transport via blood
  • Lacteals: Absorb fatty acids, glycerol, transport via lymph

Conclusion

• Part 2 of Human Nutrition covers chemical digestion and absorption
• Importance of enzymes, hydrochloric acid, bile, and villi in digestion and absorption
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