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Digestive and Excretory Systems — Free MYP4 Biology Practice Questions
1QuestionMechanical vs Chemical DigestionConcept Practice
3 marks~5 minCriterion A
The diagram below shows the human digestive system with the mouth and stomach labelled.
a
Identify the type of mechanical digestion that occurs in the mouth. [1]
b
Identify the type of chemical digestion that begins in the mouth, naming the enzyme responsible and its substrate. [1]
c
Explain why chemical digestion in the stomach is essential for protein absorption, naming the enzyme involved and describing how it acts on its substrate. [1]
Solutions
2QuestionDiseasesAssessment Practice
2 marks~3 minCriterion D
A 45-year-old patient with type 2 diabetes attends a routine clinic. Blood tests show elevated serum creatinine and a reduced estimated glomerular filtration rate (eGFR). Urine analysis reveals persistent proteinuria.
a
Explain how these blood and urine results indicate impaired kidney function, linking each finding to a specific failure in normal kidney physiology. [1]
b
Discuss one limitation of relying solely on these results to diagnose diabetic nephropathy, referring to a specific factor that may alter the accuracy of the findings. [1]
Solutions
3QuestionMechanical vs Chemical DigestionAssessment Practice
2 marks~3 minCriterion A
A patient with hypochlorhydria (insufficient gastric HCl production) is advised by their doctor to chew food more thoroughly before swallowing.
a
Explain how increased mechanical digestion in the mouth partially compensates for reduced chemical digestion in the stomach. [1]
b
State one limitation of this strategy, referring to a specific chemical function of HCl that mechanical digestion cannot replace. [1]
Solutions
4QuestionRole of Enzymes in DigestionAssessment Practice
2 marks~3 minCriterion C
The diagram shows the active site of the enzyme amylase alongside several differently shaped molecules, including starch.
a
Using the terms active site, substrate, and enzyme-substrate complex, explain how amylase specifically binds to starch. Name the model that describes this interaction. [1]
b
A student claims that raising the temperature to 80 °C would increase the rate of starch breakdown by amylase indefinitely. Evaluate this claim, referring to the shape of the active site in your answer. [1]
Solutions
5QuestionAccessory organsAssessment Practice
6 marks~9 minCriterion C
A student investigated whether bile salts are essential for pancreatic lipase to digest fats. Three test tubes each contained 5 mL of olive oil, 5 mL of water, and a pH indicator that changes colour when fatty acids are released. All tubes were maintained at 37 °C and pH 8.0.
Test tube A: pancreatic lipase only — colour change at 25 min
Test tube B: pancreatic lipase + bile salts — colour change at 5 min
Test tube C: bile salts only — no colour change observed
Test tube A: pancreatic lipase only — colour change at 25 min
Test tube B: pancreatic lipase + bile salts — colour change at 5 min
Test tube C: bile salts only — no colour change observed
a
Identify the independent variable in this experiment. [1]
b
Explain why test tube C was included in the experimental design. [2]
c
Evaluate the hypothesis: "Bile salts are essential for pancreatic lipase to digest fats." Use quantitative evidence from the data and your understanding of bile salt function in your response. [3]
Solutions
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