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7.1.10Human Nutrition

Digestion of Starch — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions

5 min read 4 parts Lesson 7 of 9 Unit quiz

📚 Cambridge IGCSE Biology 0610 Hub / Topical Revision
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Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
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Part 1 of 5Starch and Its Enzymes

Starch is a large insoluble carbohydrate that must be broken into small soluble sugars before it can be absorbed.

Amylase
  • Amylase This enzyme digests starch into smaller sugars and is made in the salivary glands and in the pancreas.
Maltose
  • Maltose Amylase breaks starch into maltose, which is a disaccharide made of two glucose units.
Maltase
  • Maltase This enzyme splits maltose into glucose and is found on the membranes of the cells lining the small intestine.
Glucose
  • Glucose The final product is glucose, a small soluble molecule that can be absorbed into the blood.

Part 2 of 5Following Starch Along the Gut

Digestion of starch begins in the mouth and is completed in the small intestine.

1
Salivary amylase is mixed with food as it is chewed, and it begins to digest starch to maltose in the mouth.
2
Food passes through the stomach, where the acidic conditions stop salivary amylase from working.
3
Pancreatic amylase is secreted into the duodenum and continues to break starch down into maltose.
4
Maltase on the membranes of the epithelial lining of the small intestine converts maltose into glucose.
5
Glucose is absorbed through the wall of the small intestine into the blood.

Part 3 of 5Summary Table

Summary Table
Substrate
  • Substrate Each enzyme acts on one substrate, so amylase works on starch and maltase works on maltose.
Active site
  • Active site The shape of the active site matches its substrate, which explains why enzymes are specific.
Optimum conditions
  • Optimum conditions Digestive enzymes work best at body temperature and at a suitable pH for the part of the gut they are in.
Chemical digestion
  • Chemical digestion Breaking large molecules into small ones by enzymes is chemical digestion and happens in addition to chewing.
SubstrateEnzymeWhere madeProduct
StarchAmylaseSalivary glands and pancreasMaltose
MaltoseMaltaseSmall intestine liningGlucose

Part 4 of 5Why Digestion Is Needed

Size of molecules
  • Size of molecules Starch molecules are too large to pass through the wall of the gut into the blood.
Solubility
  • Solubility Small soluble sugars can dissolve in the blood plasma and be carried to the cells.
Use of glucose
  • Use of glucose Glucose is used in respiration to release energy for the cells of the body.
Storage
  • Storage Extra glucose can be converted to glycogen or fat for storage.

Part 5 of 5Exam Checklist & Tips

7.1.10 – Key Points for the Exam

  • Amylase An enzyme that digests starch to maltose.
  • Maltase An enzyme that digests maltose to glucose.
  • Disaccharide A sugar made of two linked sugar units, such as maltose.
  • Duodenum The first section of the small intestine, where pancreatic secretions enter.

Common Mistakes

  • Saying amylase makes glucose directly; amylase gives maltose and maltase then gives glucose.
  • Forgetting that amylase is made in both the salivary glands and the pancreas.
  • Writing that maltase is made in the pancreas; it is found on the lining of the small intestine.
  • Describing digestion as only physical; the breakdown of starch is chemical and involves enzymes.

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