Human digestive systemIB MYP Biology: Subtopic test

1. 1
   A man in Nairobi has a gallstone that blocks the tube carrying bile from his gall bladder to his small intestine. After eating a meal of fried chicken and chips he feels sharp pain and later passes pale, greasy faeces.

   (a)

   In which organ is bile made?

   [1 mark]

   • AGall bladder
   • BLiver
   • CPancreas
   • DStomach

   (b)

   Which statement correctly describes the action of bile in the small intestine?

   [1 mark]

   • AIt digests fat into fatty acids and glycerol
   • BIt digests protein into amino acids
   • CIt neutralises stomach acid and breaks fat into small droplets
   • DIt absorbs water from the digested food

   (c)

   Explain why the man's body digests fat more slowly while the bile duct is blocked.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student in Mumbai builds a model of the gut wall. She fills a 10 cm length of Visking tubing (a partially permeable membrane) with a mixture of starch solution and glucose solution, ties both ends and places it in a beaker of distilled water at 37 °C. After 30 minutes she tests the water in the beaker. Benedict's solution turns brick-red when heated with it, but iodine solution stays orange-brown.

   (a)

   What does the Visking tubing represent in this model?

   [1 mark]

   • AThe stomach, which mixes food with acid
   • BThe liver, which makes bile
   • CThe pancreas, which makes enzymes
   • DThe wall of the small intestine, which absorbs digested food

   (b)

   Which conclusion is best supported by the student's results?

   [1 mark]

   • AGlucose molecules are small enough to pass through the tubing but starch molecules are too large
   • BStarch molecules pass through the tubing faster than glucose molecules
   • CGlucose is converted into starch inside the tubing
   • DNeither starch nor glucose can pass through the tubing

   (c)

   The student now repeats the investigation at 20 °C, 37 °C and 50 °C to find how temperature affects how quickly glucose leaves the tubing. Identify the independent variable and state one variable she must control.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   In coeliac disease the lining of the small intestine is damaged and the villi become flattened. A teenager in Sao Paulo with untreated coeliac disease loses weight and feels weak even though she eats plenty of food.

   (a)

   Explain why she loses weight even though she eats plenty of food.

   [3 marks]

   (b)

   Describe how the structure of a normal villus makes it well adapted for absorbing digested food.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A 45-year-old man in Mexico City with severe obesity is offered an operation that shortens the length of his small intestine that food passes through, so that less food is absorbed. Doctors say the operation is permanent. The health ministry must decide whether to pay for this operation for many patients.

   (a)

   Before the operation the man eats a cheese sandwich. Describe what happens to the sandwich from his mouth until its nutrients are absorbed, naming the organs and enzymes involved.

   [6 marks]

   (b)

   Discuss and evaluate whether the health ministry should pay for this operation for many patients.

   [6 marks]

   Total for question 4: 12 marks

End of questions