Biology p1

• What is the main function of enzymes in the digestive system?

  They catalyse the breakdown of food.
• What are the main components of the digestive system?

  • Salivary glands
  • Liver
  • Tongue
  • Gullet (Oesophagus)
  • Stomach
  • Gall bladder
  • Large intestine
  • Rectum
  • Pancreas
  • Small intestine
• Where are enzymes produced in the digestive system?

  They are produced by specialised cells in glands and in the gut.
• What is the role of bile in digestion?

  Bile neutralizes stomach acid and emulsifies fats.
• What enzyme is produced in the stomach?

  The protease enzyme, pepsin.
• Why does the stomach produce hydrochloric acid?

  To kill bacteria and provide the right pH for the protease enzyme to work.
• What is the pH level of the stomach acid?

  pH 2 (acidic).
• What happens in the large intestine?

  Excess water is absorbed from the food.
• What is the function of the gall bladder?

  It stores bile before it's released into the small intestine.
• What enzymes does the pancreas produce?

  Protease, amylase, and lipase enzymes.
• What is the role of the small intestine in digestion?

  It produces enzymes to complete digestion and absorbs digested food into the blood.
• What are the products of lipid digestion?

  Glycerol and fatty acids.
• What is the function of carbohydrases?

  They convert carbohydrates into simple sugars.
• What is an example of a carbohydrase?

  Amylase.
• Where is amylase produced?

  In the salivary glands, pancreas, and small intestine.
• What do proteases do?

  They convert proteins into amino acids.
• What is the function of lipases?

  They convert lipids into glycerol and fatty acids.
• What is the role of bile in relation to stomach acid?

  Bile neutralizes the stomach acid and makes conditions alkaline for enzymes to work.
• How does bile emulsify fats?

  It breaks the fat into smaller droplets, increasing the surface area for lipase to work on.
• What are the steps to prepare a food sample for testing food molecules?

  1. Break up the food using a pestle and mortar.
  2. Transfer to a beaker and add distilled water.
  3. Stir the mixture to dissolve some food.
  4. Filter the solution to remove solid bits.
• What is the procedure for the Benedict's test for sugars?


  1. Prepare a food sample and transfer 5 cm² to a test tube.
  2. Set a water bath to 75°C.
  3. Add about 10 drops of Benedict's solution.
  4. Place the test tube in the water bath for 5 minutes.
  5. Observe color change: blue to green, yellow, or brick-red indicates reducing sugars.
• How do you test for starch using iodine solution?


  1. Prepare a food sample and transfer 5 cm³ to a test tube.
  2. Add a few drops of iodine solution and shake gently.
  3. A color change from brownish-orange to black or blue-black indicates the presence of starch.
• What is the procedure for the Biuret test for proteins?

  1. Prepare a food sample and transfer 2 cm³ to a test tube.
  2. Add 2 cm³ of Biuret solution and mix gently.
  3. A color change from blue to pink or purple indicates the presence of protein.
• How do you test for lipids using Sudan III stain solution?

  1. Prepare a food sample and transfer about 5 cm³ to a test tube.
  2. Add 3 drops of Sudan III stain solution and shake gently.
  3. A bright red top layer indicates the presence of lipids.
• What should you do before starting a practical experiment?

  Conduct a risk assessment.
• Why is it important to filter the food sample before testing?

  To remove solid bits of food that could interfere with the test.
• How do the digestive enzymes work together in the digestive system?

  They break down large food molecules into smaller, absorbable ones.
• What is the significance of the alkaline conditions in the small intestine?

  They allow enzymes to work effectively for digestion.
• What is the main purpose of digestion?

  To break down food into smaller, absorbable molecules.