Practise 32 exam-style questions on The human digestive system for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
32 questions
2–6 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
3 marks
Explain how peristalsis moves food along the gut.
Model answer
Circular muscles behind the food contract and circular muscles ahead relax, creating a wave of muscle contraction that pushes food along the gut. Longitudinal muscles may also shorten segments to help movement.
Explanation
Peristalsis involves coordinated contractions and relaxations of gut muscles producing a wave that propels the food bolus along the digestive tract.
Mark scheme
1 mark
Muscle contraction in gut wall (circular muscle contracts behind food)
1 mark
Muscle ahead of food relaxes so wave of contraction pushes bolus forward
1 mark
Longitudinal muscles shorten gut segments to help movement (optional)
Award if stated; alternative wording acceptable.
Question 2
4 marks
Describe how the small intestine is adapted for absorption of the products of digestion.
Model answer
Long with a large surface area; inner surface covered with villi and microvilli increasing surface area; thin walls for short diffusion distance; good blood supply / capillaries to carry absorbed molecules away.
Explanation
Absorption is efficient in the small intestine due to large surface area from villi and microvilli, thin epithelial cells for short diffusion distance and many blood capillaries that transport absorbed nutrients.
Mark scheme
1 mark
Large surface area (villi / microvilli)
Award for either villi or microvilli or both.
1 mark
Thin walls / short diffusion distance
1 mark
Good blood supply / capillary network to transport absorbed molecules
1 mark
Long length / folds to increase surface area
Award if student mentions length or circular folds (plicae).
Question 3
4 marks
A patient with a blocked bile duct cannot release bile into the small intestine. Predict two consequences for digestion and absorption.
Model answer
Poor emulsification of fats ? reduced fat digestion by lipase ? fat malabsorption and steatorrhea; reduced neutralisation of stomach acid ? enzymes inactivated / impaired function, and deficiency of fat-soluble vitamins (A, D, E, K).
Explanation
Bile is needed to emulsify fats and neutralise acid; without it fats cannot be properly digested or absorbed, and enzyme function in the small intestine is impaired.
Mark scheme
1 mark
Reduced emulsification of fats leading to poor fat digestion
1 mark
Fat malabsorption / fatty stools (steatorrhea) and possible deficiencies in fat-soluble vitamins
1 mark
Less neutralisation of stomach acid ? pancreatic enzymes less effective
1 mark
Overall decreased absorption of fats and fat-soluble nutrients
Question 4
6 marks
A student measures the rate of starch breakdown by amylase at different temperatures. The results show a peak at 37°C and a rapid fall at 60°C. Explain these results in terms of enzyme activity, including effects of temperature.
Model answer
Increasing temperature increases kinetic energy so more enzyme-substrate collisions and higher rate, up to optimum (~37°C). Above optimum heat causes enzyme denaturation; the active site changes shape and rate falls sharply (at 60°C little activity left).
Explanation
As temperature rises enzyme activity increases to an optimum because of more frequent effective collisions. Above the optimum enzymes denature and lose their active site, drastically reducing the rate, which explains the 60°C result.
Mark scheme
1 mark
Increasing temperature increases rate due to more kinetic energy / collisions
1 mark
There is an optimum temperature (around 37°C) for maximal activity
1 mark
High temperature causes denaturation
1 mark
Denaturation changes active site shape so substrate cannot bind
1 mark
At 60°C enzyme activity is low because many enzymes are denatured
1 mark
Reference to 37°C being near human body temperature (optimum for human enzymes)
Award if mentioned.
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