Component 2.4 Exam Q Flashcards
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How is alkaline pH achieved in duodenum
Alkaline mucus - secreted by Brunners Gland
Pancreatic juice
Bile - Sodium hydrogen carbonate
Alkaline pH in the duodenum is achieved by secretions from Brunner’s glands, the pancreas, and the liver. Brunner’s glands secrete alkaline mucus rich in bicarbonate ions. The pancreas releases pancreatic juice containing sodium hydrogen carbonate (NaHCO₃), and bile from the liver also contains NaHCO₃. These secretions neutralise acidic chyme from the stomach, creating an optimal pH for enzyme activity.
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Importance of differe pH around digestive system
Different enzymes
Have different pHs
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Label and what they secrete
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Two functions of mucus secretions in digestive system
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Apart from its length, state two other ways ni which the surface area of the small intestine is increased.
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(c) Identify structures X and Y and state what is absorbed in each case.
4 marks
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What is absorbed by capillaries in villi
The capillaries in the villi of the small intestine absorb small, water-soluble nutrients from digested food.
Substances absorbed by capillaries in villi:
1. Glucose – from carbohydrate digestion
2. Amino acids – from protein digestion
3. Water
4. Vitamins – especially water-soluble vitamins (e.g. B and C)
5. Mineral ions – like sodium, potassium, calcium, etc.
Fatty acids and glycerol are not absorbed into capillaries — they go into lacteals (part of the lymphatic system).
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Define digestion
The breakdown of large insoluble molecules into smaller soluble ones
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Summary of important cells in deigestive system where they are found
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How are epithelial cells adapted to carry out function
1. Epithelial Cells (Enterocytes)
Function: Absorption of nutrients
Adaptations:
• Microvilli (brush border): Greatly increase surface area for absorption
• Thin membrane: Short diffusion pathway for nutrients
• Many mitochondria: Provide ATP for active transport of nutrients
• Tight junctions between cells: Prevent leakage of digestive products between cells
• Carrier proteins & channel proteins: For facilitated diffusion and active transport of specific nutrients
• Enzymes on brush border: e.g. peptidases and disaccharidases for final digestion at the surface
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How are goblet cells adapted to carry out function
2. Goblet Cells
Function: Secretion of mucus to protect and lubricate the lining
Adaptations:
• Goblet shape: Wide at top to store mucus granules
• Large Golgi apparatus & ER: For producing and packaging mucus
• Basal nucleus: Positioned away from mucus to allow more storage space
• Located between epithelial cells: So mucus spreads evenly along the surface
• Mucus secretion: Forms a protective barrier against digestive enzymes and acidic chyme
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Summarise Brunners Gland
Brunner’s Glands – A-Level Summary
Location:
• Found in the submucosa of the duodenum (the first part of the small intestine).
Function:
• Secrete alkaline mucus (rich in bicarbonate ions, HCO₃⁻).
• Neutralises stomach acid (chyme) entering from the stomach.
• Protects the duodenal lining from acidic damage.
• Provides an optimal pH (~7–8) for pancreatic enzyme activity.
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Digestion of fat 5 marks
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Digestion of proteins 5 marks
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