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Human Digestive System (Chapter 14) - Coggle Diagram
Human Digestive System (Chapter 14)
Importance of Digestion
Definition: Breaking down large, complex food molecules → smaller, soluble molecules.
Why important?
Absorbed into bloodstream
Used by cells for respiration (energy release)
Main Nutrients
Carbohydrates
Small / large molecules
Immediate energy
Starch (rice, bread, noodles, potatoes), Sugars (fruits), Fibre (cellulose, undigested)
Proteins
Very large molecules
Growth, repair, new cells
Meat, fish, dairy, eggs
Fats
Small, insoluble in water
Energy reserve, insulation
Butter, cheese
Human Digestive System
Processes of Digestion
Physical: chewing, grinding, churning (increase surface area)
Chemical: enzymes break down large → small molecules
Enzymes
Carbohydrates → Carbohydrases → Simple sugars
Proteins → Proteases → Amino acids
Lipases → Fats → Fatty acids + Glycerol
Properties: proteins, speed up reactions, specific, unchanged after use
Main Organs
Mouth
Physical: chewing
Chemical: carbohydrases → partially digested carbs
Oesophagus
Muscles push food down (peristalsis)
Carbohydrate digestion continues
Stomach
Physical: churning
Chemical: proteases + hydrochloric acid → partially digested proteins
Acid kills bacteria
Small Intestine
Complete digestion (carbs → sugars, proteins → amino acids, fats → fatty acids + glycerol)
Absorption into bloodstream
Bile (emulsification of fats)
Large Intestine
Absorption of water, minerals
Undigested food stored in rectum
Faeces released through anus
Issues Affecting Digestive System
Constipation
Lack of fibre / water / exercise
Gastric Pain
Bacterial/viral infection, irregular meals, excess alcohol, caffeine, oily food
Food Poisoning
Poor food handling, expired food, unsafe storage, mouldy/dented cans
Preventive Steps
Proper food storage
Separate utensils for raw/cooked food
Avoid expired/mouldy food
Buy chilled/frozen food stored properly
Beneficial Bacteria
Functions
Fight diseases
Help absorb nutrients & minerals
Produce enzymes, vitamins, amino acids
Aid digestion of some foods
Food products: coffee, cheese, miso, vinegar
