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Human Body Systems

Human Body Systems — Free MYP4 Biology Practice Questions

1QuestionAntigen-Antibody InteractionsConcept Practice

2 marks~3 minCriterion B

A student investigates how temperature affects antibody–antigen binding. The relative binding strength of five antibodies is measured at two temperatures.

Antibody	A	B	C	D	E
Binding strength at 25°C (units)	45	62	38	71	54
Binding strength at 37°C (units)	42	58	35	67	50

Identify the pattern shown in the data by comparing the binding strength values at 25°C and 37°C for all five antibodies. [1]

Analyse what the data suggest about the relationship between temperature and antibody–antigen binding strength. [1]

Solutions

2QuestionAntigen-Antibody InteractionsConcept Practice

2 marks~3 minCriterion A

The diagram below shows a Y-shaped antibody with its Fab and Fc regions labeled.

On the diagram, identify both antigen-binding sites by labeling them clearly. [1]

Explain why a single antibody molecule can bind two identical antigen molecules simultaneously. [1]

Solutions

3QuestionComponents of the Immune SystemConcept Practice

3 marks~5 minCriterion A

The diagram shows three pathogens — a bacterium, a virus, and a fungus — each displaying differently shaped surface antigens. Three antibodies (A, B, and C), each with a distinct binding site, are also shown.

Match each antibody to the pathogen it binds to. [1]

Explain how the shape of an antibody's binding site determines which antigen it can bind to. Use the terms "complementary shape" and "lock and key" in your answer. [1]

A mutated virus produces antigens with a slightly altered shape. Explain why existing antibodies produced against the original virus may no longer be effective against the mutated strain. [1]

Solutions

4QuestionRegulation of Body TemperatureConcept Practice

2 marks~3 minCriterion A

The diagram of human skin below shows several structures involved in thermoregulation. Structure X is a coiled tubular gland located in the dermis, with a duct opening onto the skin surface.

Identify structure X. [1]

Explain how structure X contributes to cooling the body when core temperature rises above the set point. [1]

Solutions

5QuestionNegative Feedback MechanismsConcept Practice

2 marks~3 minCriterion D

Closed-loop insulin pump systems continuously monitor blood glucose and automatically deliver insulin or glucagon to maintain target glucose levels in patients with Type 1 diabetes.

Outline how this device replicates a negative feedback mechanism in the human body. [1]

Discuss one ethical issue raised by the widespread use of closed-loop insulin pump technology. [1]

Solutions

6QuestionComponents and Functions of BloodConcept Practice

2 marks~3 minCriterion A

A blood smear from a patient with anaemia is examined under a light microscope. The smear shows several cell types, including large biconcave disc-shaped cells lacking a nucleus, irregularly shaped cell fragments, and cells with a visible nucleus.

On the diagram provided, label the cell responsible for oxygen transport. [1]

Explain how the structural features of this cell enable efficient oxygen transport to body tissues. [1]

Solutions

7QuestionComponents and Functions of BloodConcept Practice

2 marks~3 minCriterion D

In many countries, hospitals rely on voluntary blood donation systems to maintain safe blood supplies. Before transfusion, donated blood undergoes rigorous screening.

Outline one real-world application of blood component screening in hospitals. [1]

Describe one ethical issue that arises from relying on voluntary blood donation to meet hospital demand. [1]

Solutions

8QuestionRole of Enzymes in DigestionConcept Practice

2 marks~3 minCriterion D

Approximately 65% of the global adult population has reduced ability to digest lactose due to insufficient lactase production. Biotechnology companies have developed enzyme-based solutions to help lactose-intolerant individuals consume dairy products.

Identify one enzyme-based application used to address lactose intolerance. [1]

Discuss one ethical issue that arises from this application. [1]

Solutions

9QuestionMechanical vs Chemical DigestionConcept Practice

3 marks~5 minCriterion A

The diagram below shows the human digestive system with the mouth and stomach labelled.

Identify the type of mechanical digestion that occurs in the mouth. [1]

Identify the type of chemical digestion that begins in the mouth, naming the enzyme responsible and its substrate. [1]

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

10QuestionCentral and Peripheral Nervous SystemConcept Practice

4 marks~6 minCriterion A

The diagram below shows a spinal reflex arc. A pin pricks the skin, generating a nerve impulse that travels through three neurons before reaching a muscle.

Identify the four labelled components of the reflex arc shown in the diagram. [2]

Explain the sequence of signal transmission from the moment the pin pricks the skin until the muscle responds, describing the role of each component identified in part (a). [2]

Solutions

11QuestionComparing Nervous and Hormonal ControlConcept Practice

2 marks~3 minCriterion D

Type 1 diabetes occurs when the pancreas produces little or no insulin, a hormone that signals cells to absorb glucose from the blood. Without treatment, blood glucose rises to dangerous levels. Doctors prescribe synthetic human insulin, produced using genetically modified bacteria, which patients self-administer by injection.

Explain how synthetic insulin restores hormonal control of blood glucose in a Type 1 diabetic patient. [1]

Discuss one limitation or ethical issue associated with insulin therapy. [1]

Solutions

12QuestionCommon diseasesConcept Practice

2 marks~3 minCriterion D

Tuberculosis (TB) is a bacterial respiratory disease transmitted via airborne droplets released when an infected person coughs or sneezes. In densely populated urban areas, close proximity between individuals significantly increases transmission risk. Public health authorities must balance disease control with the rights of individuals when designing intervention policies.

Explain how knowledge of TB's airborne transmission mechanism can inform the development of one specific public health policy in densely populated urban areas. [1]

Discuss one ethical issue that may arise when implementing TB control policies in urban communities. [1]

Solutions

13QuestionProcess of breathingConcept Practice

2 marks~3 minCriterion A

The diagram shows a cross-section of the human thoracic cavity during inhalation. Four structures are labelled:

A: trachea
B: lungs
C: diaphragm
D: intercostal muscles

Identify the labelled structure that contracts and flattens to increase the volume of the thoracic cavity during inhalation. [1]

Explain how the contraction of this structure causes air to enter the lungs. [1]

Solutions

14QuestionTypes of musclesConcept Practice

2 marks~3 minCriterion D

During a 400 m sprint, fast-twitch muscle fibres rely heavily on anaerobic respiration, producing lactate and hydrogen ions that lower intracellular pH and contribute to muscle fatigue. Some athletes use buffering supplements such as sodium bicarbonate to delay this pH drop and sustain performance.

Outline one real-world application of understanding anaerobic respiration in fast-twitch muscle fibres for athletic training or performance. [1]

Discuss one ethical issue raised by the use of supplements that delay muscle fatigue in competitive sport. [1]

Solutions

15QuestionInteraction with other systemsConcept Practice

4 marks~6 minCriterion A

The diagram below shows a bicep curl: the arm moves from a fully extended position to a fully flexed position. The humerus, radius, ulna, biceps brachii, and triceps brachii are labelled.

Identify the bones that move during a bicep curl and state the type of joint present at the elbow. [2]

Explain how the biceps brachii and triceps brachii function as an antagonistic pair to produce both the flexion and extension phases of a bicep curl. [2]

Solutions

16QuestionProtection and support, homeostasisConcept Practice

2 marks~3 minCriterion D

Bone density screening using dual-energy X-ray absorptiometry (DEXA) generates T-scores, which compare an individual's bone mineral density (BMD) to a healthy young-adult reference population. Clinicians use these scores to guide decisions about fracture prevention and treatment.

Outline one real-world medical application of bone density screening. [1]

Identify one limitation of relying on T-scores alone when assessing a patient's fracture risk. [1]

Solutions

17QuestionMain partsConcept Practice

2 marks~3 minCriterion A

The diagram below shows the human skeleton with one region highlighted.

Identify the highlighted region of the skeleton. [1]

Explain one primary function of this region. [1]

Solutions

18QuestionInteraction with other systemsConcept Practice

2 marks~3 minCriterion C

Describe the trend shown in the line graph of bone density (g/cm²) versus age (years) for males and females from ages 20 to 80.

Solutions

19QuestionInteraction with other systemsConcept Practice

2 marks~3 minCriterion B

Outline the steps of a simple experiment to measure the effect of bicep contraction angle on the mechanical advantage of the forearm lever system. The diagram shows a student's arm at three angles (45°, 90°, 135°) with force arm (FA) and load arm (LA) distances labeled. Data: At 45°, FA = 4 cm, LA = 36 cm; at 90°, FA = 4 cm, LA = 32 cm; at 135°, FA = 4 cm, LA = 28 cm.

Solutions

20QuestionControl and coordinationConcept Practice

2 marks~3 minCriterion A

The diagram shows an endocrine gland secreting a hormone into the bloodstream, which subsequently reaches a target cell.

Explain how the hormone travels from the endocrine gland to the target cell. [1]

Explain how the hormone triggers a specific response only in the target cell and not in other cells it passes. [1]

Solutions

21QuestionControl and coordinationConcept Practice

2 marks~3 minCriterion A

The diagram below shows a sagittal section of the human brain. Structure X is positioned directly beneath the hypothalamus.

Identify structure X. [1]

Explain how structure X regulates hormone secretion from other endocrine glands. [1]

Solutions

22QuestionMain glands and functionsConcept Practice

2 marks~3 minCriterion D

During menopause, the ovaries progressively reduce production of oestrogen and progesterone, triggering symptoms such as hot flushes, night sweats, and accelerated bone density loss. Hormone replacement therapy (HRT) is one medical response to these changes.

Outline one real-world application of HRT in managing menopausal symptoms. [1]

Describe one ethical issue that arises from the use of HRT for menopause. [1]

Solutions

23QuestionWorkingConcept Practice

2 marks~3 minCriterion A

During a biology practical, students monitor a volunteer's blood glucose concentration over 90 minutes after consuming a glucose drink. Levels rise sharply, then return to the normal range without any medical intervention.

Describe the role of insulin in returning blood glucose to the normal range after the drink is consumed. [1]

Explain how the responses of insulin and glucagon together form a negative feedback loop that maintains blood glucose homeostasis. [1]

Solutions

24QuestionImmune Response MechanismsAssessment Practice

8 marks~12 minCriterion A

Two individuals are infected with the same pathogen on Day 0. Person A was vaccinated against this pathogen two years ago; Person B has had no prior exposure. Their serum antibody concentrations (arbitrary units) over 14 days are shown below.

Day	3	5	7	10	14
Person A IgM	5	40	100	60	20
Person A IgG	2	80	300	500	450
Person B IgM	0	10	80	200	150
Person B IgG	0	5	20	50	100

Describe the pattern of antibody class switching from IgM to IgG in Person A and in Person B. [2]

Deduce which individual is likely to experience a shorter and less severe illness, using the data to support your reasoning. [2]

Justify the difference in immune responses between Person A and Person B by discussing the roles of memory B cells and naive B cells, and evaluate how each response affects the ability to control the infection. [4]

Solutions

25QuestionVaccination and ImmunityAssessment Practice

6 marks~9 minCriterion D

A public health official is reviewing HPV vaccination policy. The basic reproduction number (

R_0

) for HPV is 4.0. Currently, 85% of the target age group is vaccinated. The herd immunity threshold is given by:

\text{Herd immunity threshold} = 1 - \frac{1}{R_0}

Calculate the herd immunity threshold for HPV. Express your answer as a percentage. [2]

The community's current vaccination coverage is 85%. Deduce whether the community has achieved herd immunity against HPV, using your answer from part (a). [2]

Some parents refuse vaccination, citing personal freedom and uncertainty about long-term effects. Discuss the ethical tension between individual autonomy and community protection, considering the impact of vaccine refusal on immunocompromised individuals who cannot be fully protected by vaccination. [2]

Solutions

26QuestionRole of White Blood CellsAssessment Practice

2 marks~3 minCriterion C

Following the introduction of the measles–mumps–rubella (MMR) vaccine, measles cases fell by over 99% in many countries, yet outbreaks still occur in under-vaccinated communities.

Explain how white blood cells produce long-term protection after MMR vaccination. [1]

Identify one ethical issue raised by mandatory childhood vaccination programmes and explain why it is ethically significant. [1]

Solutions

27QuestionRole of White Blood CellsAssessment Practice

6 marks~9 minCriterion D

A low-income country's Ministry of Health is considering reducing measles vaccination funding to reallocate resources to other priorities. Epidemiological data collected over ten years is shown below.

Year	2014	2015	2016	2017	2018	2019	2020	2021	2022	2023
Vaccination coverage (%)	85	83	80	75	70	65	60	55	50	45
Measles outbreak frequency (outbreaks/year)	2	3	4	6	8	10	12	15	18	22

Analyse the relationship between vaccination coverage and measles outbreak frequency shown in the data. [2]

Explain how vaccination stimulates memory B-cells and memory T-cells, and connect this mechanism to the concept of herd immunity for measles. [2]

Evaluate the long-term societal consequences of continuing to reduce vaccination coverage in this country, considering population density, healthcare infrastructure, and at least one environmental factor affecting vaccine delivery. [2]

Solutions

28QuestionImmune Response MechanismsAssessment Practice

5 marks~8 minCriterion C

Two patients were exposed to the same pathogen. Patient V had been vaccinated previously; Patient U had not. Antibody concentrations were recorded over 14 days.

Day (days)	2	4	6	8	10	12	14
Patient V (AU)	5	80	200	450	600	620	610
Patient U (AU)	0	5	15	40	100	250	400

Identify two differences in the antibody response patterns of Patient V and Patient U shown in the data. [1]

Explain why Patient V produces antibodies more rapidly than Patient U following exposure to the pathogen. [2]

Evaluate whether the data alone are sufficient to conclude that Patient V is experiencing a secondary immune response. Justify your reasoning with reference to both the data trends and the underlying immune mechanisms. [2]

Solutions

29QuestionRegulation of Body TemperatureAssessment Practice

4 marks~6 minCriterion A

The diagram shows a cross-section of skin with an arteriole and a sweat gland. During vigorous exercise, the arteriole widens and sweat gland activity increases.

Identify the change shown in the arteriole during exercise and name the process responsible. [1]

Explain how vasodilation of skin arterioles contributes to lowering body temperature during exercise. [2]

Evaluate how the combined action of vasodilation and increased sweat gland activity is more effective at reducing core body temperature than either response acting alone. [1]

Solutions

30QuestionRegulation of Body TemperatureAssessment Practice

3 marks~5 minCriterion A

A student exercises on a treadmill for 20 minutes. The graph shows her core body temperature rising from

37.0°C

to a plateau of approximately

38.5°C

during exercise, then gradually returning toward

37.0°C

over the following 20 minutes of rest.

Identify the trend in core body temperature during the recovery period. [1]

Explain how thermoreceptors and the hypothalamus work together to activate cooling mechanisms when body temperature exceeds the set point. [1]

Analyse why body temperature does not return to

37.0°C

instantly once exercise stops, using negative feedback principles to support your answer. [1]

Solutions

31QuestionRegulation of Body TemperatureAssessment Practice

2 marks~3 minCriterion A

During a marathon in Singapore (relative humidity ≈ 90%), athletes generate substantial metabolic heat. Sweating is the body's primary thermoregulatory response, yet runners in such conditions frequently suffer heat-related illness despite sweating profusely.

Explain why sweating is less effective at removing heat from the body when relative humidity is high. [1]

Discuss one physiological consequence and one practical limitation this poses for marathon athletes competing in tropical environments. [1]

Solutions

32QuestionNegative Feedback MechanismsAssessment Practice

5 marks~8 minCriterion C

A study measured blood glucose levels in a healthy individual and a Type 1 diabetic individual after both consumed a meal containing 75 g of carbohydrates at

t = 0

minutes.

Healthy individual (mmol/L):

t = 0

: 5.0 |

t = 30

: 7.8 |

t = 60

: 6.5 |

t = 90

: 5.5 |

t = 120

: 5.2 |

t = 150

: 5.0

Diabetic individual (mmol/L):

t = 0

: 5.0 |

t = 30

: 12.5 |

t = 60

: 14.2 |

t = 90

: 13.0 |

t = 120

: 11.8 |

t = 150

: 10.5

A student hypothesises that "both individuals use negative feedback to restore blood glucose to normal levels after the meal."

Describe the pattern of blood glucose change in each individual after the meal. [2]

Explain how negative feedback regulates blood glucose in the healthy individual. [1]

Evaluate the student's hypothesis using the data from the diabetic individual, and justify your conclusion by referring to the underlying physiological cause. [2]

Solutions

33QuestionRegulation of Body TemperatureAssessment Practice

7 marks~11 minCriterion C

A person exercises in a

35^\circ\text{C}

environment for 30 minutes. Measurements are taken every 5 minutes.

Time (min)	0	5	10	15	20	25	30
Core temperature ( $^\circ\text{C}$ )	37.0	37.2	37.5	37.8	38.0	38.1	38.1
Skin temperature ( $^\circ\text{C}$ )	33.0	33.5	34.0	34.2	34.3	34.3	34.2
Sweat rate (mL/min)	0	5	10	14	16	12	8

Describe the trend in core body temperature over the 30-minute period and explain the role of negative feedback in the response observed. [2]

Compare the changes in skin temperature and sweat rate between 0 and 20 minutes, and explain how these changes work together to regulate core temperature. [2]

Between 20 and 30 minutes, sweat rate falls from 16 mL/min to 8 mL/min while core temperature remains at

38.1^\circ\text{C}

. Analyse what this pattern suggests about the effectiveness of the negative feedback mechanism under prolonged heat stress. [3]

Solutions

34QuestionRegulation of Body TemperatureAssessment Practice

5 marks~8 minCriterion D

During a physiology study, volunteers underwent two trials.

Experiment 1 — Cold exposure ( $5^\circ C$ , 30 min)
Skin temperature:

33.5^\circ C \rightarrow 28.2^\circ C

Core temperature:

37.0^\circ C \rightarrow 36.8^\circ C

Experiment 2 — Vigorous exercise at $20^\circ C$
Skin temperature / Heat loss at 0 min:

30.5^\circ C

80\ \text{W}

Skin temperature / Heat loss at 10 min:

34.8^\circ C

450\ \text{W}

Skin temperature / Heat loss at 20 min:

35.2^\circ C

500\ \text{W}

Describe the change in skin temperature during cold exposure and identify the vascular mechanism responsible. [1]

Analyse the Experiment 2 data to explain how vasodilation and one additional mechanism together account for the observed increase in heat loss. [2]

Evaluate the hypothesis: "Vasodilation is the primary mechanism for heat loss during exercise, while vasoconstriction is the primary mechanism for heat conservation during cold exposure." Use evidence from both experiments and consider whether the hypothesis provides a complete account of thermoregulation. [2]

Solutions

35QuestionStructure and Function of the HeartAssessment Practice

4 marks~6 minCriterion A

The diagram below shows a frontal section of the human heart.

Label the four chambers and two major blood vessels indicated on the diagram: right atrium, right ventricle, left atrium, left ventricle, aorta, pulmonary artery. [2]

Explain the function of the left ventricle, using appropriate anatomical terminology. [1]

A patient's left ventricular wall is significantly thinner than normal due to disease. Analyse how this structural change would affect the delivery of oxygenated blood to the body's tissues. [1]

Solutions

36QuestionBlood Vessels: Arteries, Veins, CapillariesAssessment Practice

3 marks~5 minCriterion B

The table below summarises structural data for five blood vessels.

Vessel	Wall thickness	Lumen size	Valves	Direction of flow
Aorta	Very thick	Medium	No	Away from heart
Vena cava	Thin	Large	Yes	Toward heart
Pulmonary artery	Thick	Medium	No	Away from heart
Pulmonary vein	Thin	Large	Yes	Toward heart
Capillary	Very thin	Very small	No	Either

Identify the two structural features that consistently distinguish vessels carrying blood away from the heart from those carrying blood toward the heart. [1]

The renal artery carries blood away from the heart to the kidney. Deduce its wall thickness, lumen size, and whether valves are present. Justify your deduction by referring to the pattern in the data. [2]

Solutions

37QuestionStructure and Function of the LungsAssessment Practice

2 marks~3 minCriterion C

Emphysema is a lung disease in which alveolar walls are progressively destroyed. Healthy alveoli have structural adaptations — including a large surface area, thin walls, and a dense capillary network — that maximise gas exchange efficiency.

Explain how a doctor uses knowledge of alveolar structure to account for the low blood oxygen levels observed in emphysema patients. [1]

Evaluate one limitation of using a model that focuses solely on alveolar structure to explain the full clinical picture of emphysema. [1]

Solutions

38QuestionStructure and Function of the LungsAssessment Practice

8 marks~12 minCriterion C

A study investigated whether surfactant deficiency causes alveolar collapse in respiratory distress syndrome (RDS). Lung fluid samples were collected from premature infants and surface tension was measured. A lower surface tension value indicates more effective surfactant activity.

Surface tension (mN/m):
Healthy premature infants: 15
Premature infants with RDS: 28

Identify the independent variable and the dependent variable in this experiment. [2]

Explain how surfactant normally prevents alveolar collapse during exhalation. [2]

Evaluate the extent to which these data support the hypothesis that surfactant deficiency causes alveolar collapse in RDS. [4]

Solutions

39QuestionStructure and Function of the LungsAssessment Practice

4 marks~6 minCriterion D

A 45-year-old patient has smoked 20 cigarettes per day for 20 years. Lung function tests confirm reduced gas exchange efficiency and impaired mucociliary clearance.

Describe one specific way smoking damages the alveoli and explain how this reduces gas exchange efficiency. [2]

The patient's government is considering a complete ban on tobacco sales. Discuss the ethical responsibilities of a government when introducing such a policy, considering both the duty to minimise harm to society and the right of individuals to make their own choices. [2]

Solutions

40QuestionGas Exchange and Role of AlveoliAssessment Practice

4 marks~6 minCriterion A

The diagram below shows an alveolus adjacent to a blood capillary. The partial pressure of oxygen (

pO_2

) in the alveolus is 100 mmHg; in the incoming blood it is 40 mmHg. The walls of both the alveolus and the capillary are each one cell thick.

Explain the direction of oxygen movement between the alveolus and the blood, using the terms diffusion gradient and partial pressure in your answer. [2]

The alveolus has two structural features that maximise the efficiency of gas exchange: thin walls and a large surface area. For each feature, explain how it contributes to efficient gas exchange. [2]

Solutions

41QuestionMechanical vs Chemical DigestionAssessment Practice

2 marks~3 minCriterion A

During a school investigation into digestion, students observed that food undergoes significant changes in both the mouth and the stomach before nutrients can be absorbed.

State one example of mechanical digestion and one example of chemical digestion that occur in the mouth, naming the enzyme involved. [1]

Explain how the stomach carries out both mechanical and chemical digestion, and justify why the acidic environment is essential for protein digestion to proceed efficiently. [1]

Solutions

42QuestionOrgans of the Digestive Tract and Their FunctionsAssessment Practice

6 marks~9 minCriterion B

The table below shows the time taken for starch to be completely digested by amylase at different pH levels. A shorter digestion time indicates higher enzyme activity.

pH level	2	4	6	7	8	10
Digestion time (min)	60	45	15	5	8	40

Identify the pH at which amylase activity is highest and state the organ of the digestive tract where this pH is typically found. [2]

Describe the trend in amylase activity as pH increases from 2 to 10, referring to the data. [2]

Analyse why starch digestion is still observed at pH 2, given that amylase is not produced in the stomach and that HCl is secreted there. [2]

Solutions

43QuestionDiseasesAssessment 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.

Explain how these blood and urine results indicate impaired kidney function, linking each finding to a specific failure in normal kidney physiology. [1]

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

44QuestionMechanical 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.

Explain how increased mechanical digestion in the mouth partially compensates for reduced chemical digestion in the stomach. [1]

State one limitation of this strategy, referring to a specific chemical function of HCl that mechanical digestion cannot replace. [1]

Solutions

45QuestionRole 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.

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]

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

46QuestionAccessory 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

Identify the independent variable in this experiment. [1]

Explain why test tube C was included in the experimental design. [2]

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

47QuestionCentral and Peripheral Nervous SystemAssessment Practice

4 marks~6 minCriterion A

A person accidentally touches a hot surface and immediately withdraws their hand. The diagram shows the reflex arc involved, with the following labeled components: a skin receptor in the hand, a sensory neuron, a relay neuron within the spinal cord, a motor neuron, and the arm muscle. Arrows indicate the direction of signal travel.

Identify the division of the nervous system in which the relay neuron operates, and state its role in this reflex arc. [1]

Describe the sequence of signal transmission from the skin receptor to the arm muscle, naming each neuron and the direction of travel at each stage. [2]

Explain why the hand begins to withdraw before the person consciously feels pain. [1]

Solutions

48QuestionCentral and Peripheral Nervous SystemAssessment Practice

5 marks~8 minCriterion A

When a person touches a hot stove, their hand withdraws before they consciously feel pain. A sensory neuron in the finger detects heat and carries a nerve impulse to the spinal cord. Inside the spinal cord, the signal synapses with an interneuron, which synapses with a motor neuron that contracts the arm muscles. Simultaneously, a separate signal travels up the spinal cord to the brain, arriving approximately 0.2 seconds after the reflex is already initiated.

Describe the afferent pathway of the reflex arc, naming the structures the nerve impulse passes through from the finger to the spinal cord. [1]

Explain how the spinal cord circuit completes the reflex arc and produces a motor response. [2]

Using the 0.2-second delay as evidence, justify the conclusion that the reflex arc is faster than a conscious response. [2]

Solutions

49QuestionStructure and Function of the Nervous SystemAssessment Practice

5 marks~8 minCriterion C

A researcher hypothesises that spinal reflexes are faster than voluntary responses because they bypass the brain. She measures the patellar reflex time and the hand-squeeze reaction time in 10 healthy adults. The graph shows individual results for both responses.

Patellar reflex times	approximately 0.02–0.03 s	low variability.
Hand-squeeze reaction times	approximately 0.15–0.25 s	high variability.

Describe the neural pathway for the patellar reflex. [1]

Explain why the hand-squeeze reaction time is longer and more variable than the patellar reflex time, referring to the neural pathway of each response. [2]

Evaluate the extent to which the data supports the researcher's hypothesis. [2]

Solutions

50QuestionReflex Arcs and Response to StimuliAssessment Practice

3 marks~5 minCriterion B

The bar graph below shows the average reaction times and synapse counts for three spinal/cranial reflex arcs.

Patellar reflex	1 synapse	50 ms
Withdrawal reflex	3 synapses	150 ms
Pupillary light reflex	2 synapses	200 ms

State the relationship between synapse number and reaction time shown by the patellar and withdrawal reflexes. [1]

Explain how synaptic delay accounts for the difference in reaction time between the patellar reflex and the withdrawal reflex. [1]

The pupillary light reflex has fewer synapses than the withdrawal reflex yet a longer reaction time. Analyse what this reveals about the factors that determine reaction time in a reflex arc. [1]

Solutions

51QuestionCommon disordersAssessment Practice

3 marks~5 minCriterion C

A patient diagnosed with Parkinson's disease had their tremor severity recorded every six months using a scale of 0 to 10.

Months since diagnosis	0	6	12	18	24	30	36
Tremor severity (0–10)	2	3	5	6	7	9	10

Identify the overall trend in tremor severity between 0 and 36 months. [1]

Explain how the progressive loss of dopamine-producing neurons in the substantia nigra leads to impaired movement control. [1]

Analyse how the data support the view that neuronal loss in Parkinson's disease is a continuous, progressive process. [1]

Solutions

52QuestionCentral and Peripheral Nervous SystemAssessment Practice

8 marks~12 minCriterion D

Brain-computer interfaces (BCIs) are implanted devices that record neural signals from the motor cortex and translate them into commands controlling external devices such as robotic limbs. For patients with paralysis, BCIs can restore environmental control. However, long-term BCI use can cause cortical remapping: motor and somatosensory areas reorganize to prioritize the BCI-controlled device over natural limb movements. Manufacturing BCIs requires rare earth metals, and removed or obsolete implants enter the electronic waste stream.

Explain how neural plasticity underlies cortical remapping during BCI use, and discuss the potential loss of natural neural function. [3]

Analyse one societal consequence of increased patient dependency on BCI technology. [2]

Evaluate the environmental impact of implanted BCI devices, considering both their production and disposal phases. [2]

Discuss one limitation of current knowledge of neural plasticity that reduces confidence in predicting the long-term effects of BCI use. [1]

Solutions

53QuestionProcess of breathingAssessment Practice

8 marks~12 minCriterion D

A city of 2 million people has recorded steadily rising concentrations of fine particulate matter (PM2.5) from industrial emissions over 20 years. Over the same period, diagnosed cases of asthma and chronic obstructive pulmonary disease (COPD) have doubled. Epidemiologists are debating whether the pollution is responsible for the increase in respiratory disease.

Explain how chronic exposure to PM2.5 disrupts the normal process of breathing and contributes to the development of asthma and COPD. [3]

Discuss the societal costs arising from the doubled rate of respiratory disease, considering both direct healthcare expenditure and indirect economic effects. [3]

Analyse the limitations of using the correlation between rising PM2.5 levels and increased respiratory disease cases to conclude that PM2.5 causes these diseases. [2]

Solutions

54QuestionCommon diseasesAssessment Practice

6 marks~9 minCriterion B

The table below summarises four respiratory diseases.

Disease — Onset — Primary symptom — Spirometry pattern

Asthma — Intermittent/acute — Wheeze — Obstructive (reversible)
COPD — Gradual/chronic — Productive cough with sputum — Obstructive (irreversible)
Pneumonia — Acute — Productive cough with fever — Restrictive
Pulmonary fibrosis — Gradual/chronic — Dry cough — Restrictive (irreversible)

Bronchiectasis is characterised by permanent dilation of the bronchi caused by chronic inflammation and recurrent infections, leading to irreversible structural damage of the airway walls and mucus hypersecretion.

Identify the relationship between disease onset and spirometry pattern shown in the table. [1]

Deduce the likely symptom progression and spirometry pattern for a patient with bronchiectasis, using evidence from the table to support your reasoning. [2]

Discuss how the biological mechanisms of airway wall damage and mucus hypersecretion in bronchiectasis produce its characteristic spirometry pattern, distinguishing it from the mechanisms responsible for the spirometry patterns seen in asthma and pulmonary fibrosis. [3]

Solutions

55QuestionProcess of breathingAssessment Practice

6 marks~9 minCriterion C

A 45-year-old patient arrives at the emergency department following a car accident with a collapsed lung (pneumothorax). Air has entered the pleural cavity, eliminating the normal pressure difference between the pleural space and the atmosphere. The attending doctor inserts a chest tube to remove this air and restore normal breathing mechanics.

Explain how negative intrapleural pressure keeps the lungs expanded and facilitates air entry during inhalation. [2]

Explain how inserting a chest tube restores normal breathing mechanics in this patient, and describe one health consequence of leaving a pneumothorax untreated. [2]

Analyse the ethical tension a doctor faces when performing an emergency chest tube insertion on a patient who is unconscious and unable to provide informed consent. [2]

Solutions

56QuestionProcess of breathingAssessment Practice

4 marks~6 minCriterion A

The diagram below shows the thoracic cavity during inhalation, with the rib cage raised and the diaphragm flattened.

Identify the two muscles that contract during inhalation and describe the movement each produces. [1]

Explain how these muscle contractions cause a change in thoracic volume and, using Boyle's law, explain the resulting pressure change inside the lungs. [2]

A student claims that air would still enter the lungs even if intrapulmonary pressure only fell to exactly atmospheric pressure. Evaluate this claim. [1]

Solutions

57QuestionMain organsAssessment Practice

6 marks~9 minCriterion C

A 45-year-old patient with a 20-year smoking history is diagnosed with chronic bronchitis and emphysema. Spirometry reveals a significantly reduced

\text{FEV}_1

(forced expiratory volume in 1 second), though diffusion capacity (

\text{DLCO}

) testing shows an even greater proportional decline.

Describe the mechanisms by which chronic smoking damages the trachea, bronchi, and alveoli. [2]

Explain how the structural damage caused by emphysema reduces the efficiency of gas exchange in the alveoli, with reference to Fick's law of diffusion. [2]

Using the spirometry data above, discuss the limitations of relying solely on

\text{FEV}_1

to evaluate the full extent of smoking-related respiratory damage. [2]

Solutions

58QuestionMain organsAssessment Practice

6 marks~9 minCriterion D

The diagram below shows a single alveolus surrounded by a capillary network. The alveolar wall consists of a single layer of epithelial cells coated with surfactant.

Gas exchange data for healthy and emphysema-affected lungs are summarised below.

Condition: Healthy / Emphysema
Oxygen diffusion rate (mL/min): 250 / 90
Alveolar surface area (m²): 80 / 50
Alveolar wall thickness (μm): 0.5 / 2.0

Explain how two structural features of the alveolus contribute to efficient gas exchange. [2]

Analyse the data to explain how the changes in surface area and wall thickness in emphysema account for the observed reduction in oxygen diffusion rate. [2]

Evaluate whether the partial pressure gradient alone is sufficient to explain the rate of oxygen diffusion across the alveolar–capillary membrane, referring to both healthy and emphysema conditions. [2]

Solutions

59QuestionCommon problemsAssessment Practice

5 marks~8 minCriterion B

An athlete's grip endurance is measured as the time (in seconds) until fatigue during a sustained handgrip contraction. Five athletes were tested before and immediately after a 60-second sprint.

Athlete	A	B	C	D	E
Before sprint (s)	45	52	38	60	47
After sprint (s)	22	28	15	35	25

Calculate the decrease in grip endurance time for each athlete. Analyse the data to identify the pattern and explain, with reference to a named physiological mechanism, why sprinting reduces muscle endurance. [2]

Propose an experiment to investigate whether a 30-second rest interval between the sprint and the grip test produces less muscle fatigue than a 60-second rest interval. Your proposal must include: the independent and dependent variables; at least two control variables; a step-by-step procedure; and one method each to ensure reliability and validity. [3]

Solutions

60QuestionInteraction with other systemsAssessment Practice

3 marks~5 minCriterion A

The graph below shows the force of contraction of a single motor unit at increasing frequencies of nerve impulses. At low frequency, isolated twitches occur. As frequency rises, successive contractions increase slightly in force (treppe). At sufficiently high frequency, contractions fuse into a single sustained maximal contraction (tetanus).

Describe the trend shown in the graph between nerve impulse frequency and force of contraction. [1]

Explain the biological mechanism that produces treppe. [1]

Explain why tetanus produces a greater and sustained force compared with a single twitch. [1]

Solutions

61QuestionHow muscles workAssessment Practice

3 marks~5 minCriterion A

The graph below shows how sarcomere length affects the force of contraction in a skeletal muscle fibre.

Describe the trend shown in the graph. [1]

Using the sliding filament theory, explain why force is greatest at a sarcomere length of 2.0–2.2 μm. [1]

A muscle that has been overstretched to a sarcomere length of 3.5 μm generates almost no force. Analyse why this occurs and predict what would happen to force if the sarcomere were then compressed to 1.0 μm. [1]

Solutions

62QuestionHow muscles workAssessment Practice

5 marks~8 minCriterion D

An experiment measured sarcomere length and tension during a single muscle contraction.

Sarcomere length (

\mu

m): 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6

Tension (relative units): 10, 45, 80, 95, 100, 90, 60, 25, 5

State the sarcomere length at which maximum tension is produced and describe the trend in tension as sarcomere length increases beyond this point. [1]

Explain how the degree of overlap between actin and myosin filaments determines the tension a sarcomere can generate, using the sliding filament theory. [2]

Justify the conclusion that reduced actin–myosin filament overlap is responsible for the decline in tension at sarcomere lengths greater than 2.8

\mu

m, using specific data from the table in your reasoning. [2]

Solutions

63QuestionCommon problemsAssessment Practice

5 marks~8 minCriterion C

During intense exercise, muscles produce lactate as a by-product of anaerobic respiration. A study investigated whether lactic acid buildup directly causes muscle fatigue.

Three groups of ten athletes each were assessed:
Sprint group: 30-second sprint intervals
Jog group: steady-state jogging at 60% maximum heart rate
Control group: rested

Blood lactate (mmol/L) measured immediately after:

Sprint	12.1	14.5	11.8	13.2	15.0	10.9	16.2	12.7	13.9	14.1
Jog	2.3	2.1	2.5	2.0	2.4	2.2	2.6	2.3	2.1	2.4
Control	1.0	0.9	1.1	1.0	1.2	0.8	1.0	1.1	0.9	1.0

All athletes reported muscle fatigue after sprinting; none reported fatigue after jogging.

Calculate the mean blood lactate concentration for each group. [1]

Describe the trend in lactate concentration across the three groups and identify one anomaly in the sprint data, justifying your choice. [2]

Evaluate the hypothesis that lactic acid buildup directly causes muscle fatigue, using the data and identifying two limitations of the experimental design that affect this conclusion. [2]

Solutions

64QuestionCommon problemsAssessment Practice

6 marks~9 minCriterion C

During a high-intensity cycling test, blood lactate concentration (mmol/L) was recorded for three athletes:

Time — Untrained — Moderately Trained — Elite

Rest: 1.0	0.8	0.6
After 1 min: 3.5	2.8	1.9
After 5 min: 8.2	5.1	3.0
After 10 min: 10.5	4.0	1.2

Describe the pattern of blood lactate accumulation for the untrained athlete over the 10-minute exercise period, using data from the table. [2]

Identify which athlete demonstrates the fastest lactate clearance after the 5-minute peak and explain how training level correlates with this ability. [2]

Analyse how the muscular system responds to sustained high-intensity exercise to produce lactate, and evaluate why lactate accumulation is greater in untrained athletes. [2]

Solutions

65QuestionCommon problemsAssessment Practice

2 marks~3 minCriterion D

A pharmaceutical company develops a new drug that significantly reduces bone fractures in elderly patients with osteoporosis. The annual cost per patient is 12 000 dollars — unaffordable for many without comprehensive insurance.

Identify one ethical issue arising from the drug's high cost and its use in elderly patients, and explain how this issue affects healthcare equity. [2]

Solutions

66QuestionInteraction with other systemsAssessment Practice

4 marks~6 minCriterion B

A diagram shows a cross-section of a healthy femur (thigh bone) under normal weight-bearing load. The bone has a balanced distribution of osteoblasts (bone-building cells) and osteoclasts (bone-resorbing cells), resulting in stable bone density. The diagram includes arrows indicating the direction of mechanical force from body weight.

[2 marks] Predict how the bone structure (specifically bone density and shape) would change after 6 months of doubled mechanical load (e.g., from heavy weightlifting).

[2 marks] Predict what would happen if, after those 6 months, the load were halved for another 6 months (e.g., the person becomes sedentary).

[2 marks] Using the concept of Wolff's law (bone adapts to the loads under which it is placed) and the interaction between the skeletal and muscular systems, justify your predictions.

Solutions

67QuestionMain partsAssessment Practice

6 marks~9 minCriterion A

The diagram below shows a labelled femur with the following structures identified: proximal epiphysis, distal epiphysis, diaphysis (shaft), periosteum, compact bone, spongy bone, medullary cavity, and articular cartilage.

The table below shows average bone density measured at the femur neck in healthy adults:

Age group (years)	20–29	30–39	40–49	50–59	60–69	70–79
Bone density ( $\text{g/cm}^2$ )	0.95	0.93	0.90	0.85	0.78	0.70

Identify the bone layer visible in the diagram that primarily resists compressive forces during weight-bearing, and describe how its structure enables this function. [2]

Analyse the trend in bone density shown in the table and explain how the change observed after age 50 affects the femur's ability to support body weight. [2]

Justify why the medullary cavity is located in the diaphysis rather than the epiphyses, referring to the functional roles of both regions. [2]

Solutions

68QuestionWorking with musclesAssessment Practice

3 marks~5 minCriterion C

The diagram shows a human arm bent at 90° at the elbow. The biceps is shown contracted and bulging; the triceps is shown relaxed and elongated.

Identify which muscle is contracting and which is relaxing in the diagram. [1]

Explain how the biceps and triceps work together as an antagonistic pair to produce the bending movement shown. [1]

A person holds a heavy bag, keeping the arm bent at 90°. Evaluate whether the triceps is completely inactive in this position. [1]

Solutions

69QuestionControl and coordinationAssessment Practice

8 marks~12 minCriterion C

Two patients, A and B, each consumed a 75 g glucose meal. Blood glucose and insulin were measured over 120 minutes.

Time (min): 0, 30, 60, 90, 120

Patient A — glucose (mmol/L)	5.0	8.2	7.6	6.1	5.2
Patient A — insulin (mU/L)	10	45	38	22	12

Patient B — glucose (mmol/L)	5.2	9.8	11.5	12.1	11.8
Patient B — insulin (mU/L)	9	18	15	10	8

Describe the changes in blood glucose and insulin levels for Patient A between 0 and 120 minutes. [2]

Analyse the relationship between blood glucose and insulin in Patient B, and explain why glucose homeostasis is not achieved. [3]

Evaluate whether the data support a diagnosis of pancreatic beta cell dysfunction in Patient B, rather than a failure of target cells to respond to insulin. Justify your reasoning using specific values from the data. [3]

Solutions

70QuestionHomeostasisAssessment Practice

6 marks~9 minCriterion C

A study measured blood glucose and insulin levels in a healthy individual and a Type 1 diabetic following a meal.

Time after meal (min)	0	30	60	120	180	240
Healthy blood glucose (mmol/L)	4.5	6.8	5.2	4.8	4.6	4.5
Healthy insulin (mU/L)	10	45	38	20	12	10
Diabetic blood glucose (mmol/L)	4.5	8.5	10.2	12.0	13.5	14.8
Diabetic insulin (mU/L)	5	6	5	5	5	5

Describe the relationship between blood glucose and insulin levels in the healthy individual over the 240-minute period. [2]

Explain why the diabetic individual's blood glucose continues to rise after the meal, using the data to support your answer. [2]

Analyse whether the data support the conclusion that negative feedback regulation of blood glucose is fully non-functional in the Type 1 diabetic. Justify your reasoning with reference to both datasets. [2]

Solutions

71QuestionWorkingAssessment Practice

4 marks~6 minCriterion D

A 50-year-old woman is considering Hormone Replacement Therapy (HRT) to manage severe menopause symptoms — hot flashes and sleep disturbances. HRT restores estrogen levels. However, long-term combined estrogen-progestin therapy is associated with a small increased risk of breast cancer (approximately 8 additional cases per 10,000 women per year) and blood clots (approximately 18 additional cases per 10,000 women per year).

Refer to the diagram of the hypothalamus–pituitary–ovary axis.

Explain how rising estrogen levels regulate their own production through negative feedback, including the roles of the hypothalamus and anterior pituitary gland. [1]

Discuss the ethical dilemma the woman faces when deciding whether to take HRT, considering the trade-off between quality of life and the statistical health risks given above. [1]

Evaluate why the population-level risk statistics provided may not accurately reflect this individual woman's actual risk of harm from HRT. [2]

Solutions

72QuestionControl and coordinationAssessment Practice

2 marks~3 minCriterion A

In individuals with Type 1 diabetes, the pancreas produces little or no insulin, causing blood glucose to rise to dangerous levels after meals.

Explain how insulin injections help restore blood glucose to within the normal physiological range. [1]

Identify one limitation of insulin injection therapy that means it cannot be considered a cure for diabetes. [1]

Solutions