Mark Scheme

Section A — Structured Questions

Question 1

(a) 5.3 (allow 5.33) [1]

(b) Any two from:

• As distance increases, the number of bubbles decreases [1]
• Light intensity decreases with distance / light is the independent variable [1]
• Number of bubbles indicates rate of photosynthesis / oxygen production [1]

[2 max]

(c) carbon dioxide + water → glucose + oxygen [1] for correct reactants [1] for correct products

Accept: CO₂ + H₂O → C₆H₁₂O₆ + O₂ (must be balanced for both marks)

[2]

(d) Any three from:

• Another factor is limiting (the rate of photosynthesis) [1]
• Such as carbon dioxide (concentration) / temperature / chlorophyll [1]
• At 10 cm, light is not the limiting factor / light intensity is high enough that another factor limits [1]
• So increasing light intensity (further) does not increase rate proportionally [1]

[3 max]

(e) Any one from:

• Use the same piece of pondweed / same mass/length/age of pondweed [1]
• Keep temperature constant / use water bath / thermostatically controlled environment [1]
• Keep CO₂ concentration constant / use same water / add sodium hydrogencarbonate [1]
• Use the same lamp / same light source [1]
• Leave for same time period / count bubbles for same duration [1]

[1 max]

Total for Question 1: 9 marks

Question 2

(a) Right atrium [1]

Accept: RA

(b) Aorta [1]

(c) Any two from:

• Prevent backflow / prevent blood flowing backwards [1]
• (Ensure) blood flows in one direction only [1]
• Prevent blood flowing from ventricles back to atria / from arteries back to ventricles [1]

[2 max]

(d) Any three from:

• (Chamber C is the) left ventricle [1]
• Which pumps blood around the (whole) body / to the body [1]
• (Chamber A is the) right atrium which receives blood (from the body) / only pumps to adjacent ventricle [1]
• Greater pressure / force is needed / must pump further / must overcome greater resistance [1]
• Thicker muscle (wall) can contract more strongly / generate higher pressure [1]

[3 max]

(e) Any four from:

• Coronary arteries supply the heart muscle / cardiac muscle with blood [1]
• (Reduced blood flow means) less oxygen / glucose reaches heart muscle [1]
• Less aerobic respiration (in cardiac muscle cells) [1]
• Less energy / ATP released (for muscle contraction) [1]
• During exercise, heart muscle needs more energy / oxygen [1]
• (Anaerobic respiration occurs producing) lactic acid, which causes pain [1]

[4 max]

Total for Question 2: 11 marks

Question 3

(a) Having two identical alleles / two copies of the same allele (for a gene) [1]

Accept: two dominant alleles or two recessive alleles (if example given) Reject: two same genes

(b) Parents' genotypes: RR × rr [1] Gametes' genotypes: R (and) r [1] Offspring genotypes: (all) Rr [1] Offspring phenotypes: (all) red [allow 1 mark if stated elsewhere]

[3]

(c)

[1] for correct Punnett square structure with gametes [1] for all offspring genotypes correct [1] for ratio 3:1 (red:white) or 3 red to 1 white

Accept: 75% red, 25% white

[3]

(d) Any two from:

• Fertilisation is random / chance / probability [1]
• Small sample size so results vary from expected ratio [1]
• (Observed ratio 89:26 =) 3.4:1 which is close to 3:1 / within expected range [1]

[2 max]

Total for Question 3: 9 marks

Question 4

(a) (Population) increases / grows (rapidly) [1]

Accept: exponential growth / exponential increase Reject: just "changes"

(b) At 2 hours = 10,000 (bacteria) / 10 thousand At 6 hours = 900,000 (bacteria) / 900 thousand [1] for reading values

900 ÷ 10 = 90 (times bigger) Number of doublings = between 6 and 7 (doublings) / approximately 6.5 doublings [1]

OR:

Working shown: 10 → 20 → 40 → 80 → 160 → 320 → 640 (6 doublings gets to 640 thousand, 7 doublings gets to 1280 thousand, so answer is between 6 and 7)

Accept: working showing 2⁶ = 64 (not quite enough) and 2⁷ = 128 (too much)

[2]

(c) Any three from:

• Limiting factor(s) restrict growth / nutrients run out [1]
• Such as: lack of food / nutrients / glucose / substrate [1]
• Build-up of toxic / waste products / CO₂ [1]
• Lack of oxygen (if aerobic respiration) [1]
• Lack of space [1]
• Death rate equals reproduction rate / birth rate [1]

[3 max]

(d) Any four from:

• (Random) mutation produces antibiotic resistance / resistant allele [1]
• Antibiotic kills non-resistant bacteria [1]
• Resistant bacteria survive and reproduce [1]
• (Resistant bacteria) pass on resistance allele to offspring / next generation [1]
• (With overuse) resistant bacteria have a selective advantage / increased selection pressure [1]
• Frequency of resistance allele increases in population [1]
• This is natural selection / evolution [1]

[4 max]

(e) Any two from:

• (Because) antibiotic-resistant bacteria are becoming more common / harder to treat infections [1]
• May lead to untreatable infections / more deaths from bacterial infections [1]
• To provide alternative treatments / to kill resistant bacteria [1]
• Reduce reliance on antibiotics [1]

[2 max]

Total for Question 4: 12 marks

Question 5

(a) Change in length / original length × 100 [1]

= -2 / 50 × 100 = -4.0 (%) [1]

Accept: -4

[2]

(b) Any two from:

• As concentration increases, percentage change decreases [1]
• (Percentage change goes) from positive / increase to negative / decrease [1]
• (Or specific values) e.g., at 0.0 mol/dm³ = +14%, at 1.0 mol/dm³ = -16% [1]
• (Shows) negative correlation / inverse relationship [1]

[2 max]

(c) Approximately 0.4 mol/dm³ / between 0.4 and 0.6 mol/dm³ [1]

(Because) this is where change is zero / closest to zero / no net movement of water [1]

Accept: 0.5 mol/dm³ for first mark

[2]

(d) Any four from:

• Water moves into cells / potato tissue by osmosis [1]
• Osmosis is the movement of water from high water potential to low water potential / from dilute to concentrated solution [1]
• Across a partially permeable membrane [1]
• Water potential in solution is higher than in potato cells / solution is more dilute (hypotonic) than cell contents [1]
• Cells become turgid / increase in volume [1]
• So (tissue) increases in length [1]

[4 max]

(e) (Percentage allows comparison) because the initial length / size / mass might vary (between samples) [1]

Accept: removes effect of different starting sizes Accept: standardises the results

[1]

Total for Question 5: 13 marks

Section B — Extended Response

Question 6: 9 marks

Level 3 (7-9 marks): A comprehensive discussion that includes:

• Clear explanation of enzyme action including active site and specificity
• Detailed analysis of the results showing pH 7 is optimum with reference to data
• Explanation of effects of pH on enzyme structure (denaturation)
• Discussion of temperature and substrate concentration effects on enzyme activity
• Evaluation of industrial applications with advantages and/or limitations
• Logical structure and specialist terminology used accurately throughout

Level 2 (4-6 marks): A reasonable discussion that includes:

• Basic explanation of how enzymes work (active site mentioned)
• Some analysis of results (identifying optimum pH)
• Some explanation of pH or temperature effects on enzymes
• Reference to industrial use
• Some use of specialist terminology, generally accurate

Level 1 (1-3 marks): A limited discussion that includes:

• Simple statement about enzymes (e.g., they break down substrates)
• Limited reference to the data
• Basic statement about factors affecting enzymes
• Little or no logical structure
• Limited use of specialist terminology

0 marks: No relevant content

Indicative content:

Enzyme structure and function:

• Enzymes are biological catalysts that speed up reactions
• Have an active site that is complementary to the substrate
• Enzyme-substrate complex forms
• Lock and key model / induced fit model
• Products released, enzyme can be reused

Analysis of results:

• Optimum pH is 7 (fastest rate = 60 seconds)
• At pH 6 and pH 8, rate is reduced
• At pH 4 and pH 10, rate is much slower (420s and 360s)
• Shows bell-shaped curve / enzyme activity varies with pH

Effect of pH:

• pH affects the shape of the active site
• Extreme pH denatures the enzyme
• Breaks bonds (hydrogen/ionic) holding the enzyme structure
• Active site changes shape
• Substrate no longer fits / fewer enzyme-substrate complexes form

Other factors:

• Temperature affects enzyme activity
• Increased kinetic energy increases collisions
• Above optimum temperature, enzyme denatures
• Substrate concentration affects rate (if substrate is limiting)
• Enzyme concentration affects rate

Industrial applications:

• Biological washing powders work at lower temperatures (save energy)
• Specific enzymes break down specific stains (proteases for protein, lipases for fat)
• Food production: amylase in bread making / converting starch to sugar
• Issues: may cause allergies, enzymes denatured at high temperatures, expensive to produce

Question 7: 9 marks

Level 3 (7-9 marks): A comprehensive evaluation that includes:

• Detailed analysis of the graph showing steady increase from ~315 to ~415 ppm
• Clear explanation of causes (combustion of fossil fuels, deforestation, etc.)
• Detailed explanation of effects on ecosystems (greenhouse effect, climate change mechanisms)
• Evaluation of multiple impacts on biodiversity with specific examples
• Consideration of both direct and indirect effects
• Logical structure and specialist terminology used accurately throughout

Level 2 (4-6 marks): A reasonable evaluation that includes:

• Some analysis of the graph data
• Some explanation of causes of increased CO₂
• Some description of effects on ecosystems or biodiversity
• Limited evaluation of impacts
• Some use of specialist terminology, generally accurate

Level 1 (1-3 marks): A limited evaluation that includes:

• Basic reference to the graph showing increase
• Simple statement about cause (e.g., burning fossil fuels)
• Simple statement about effect (e.g., global warming)
• Little or no evaluation
• Limited use of specialist terminology

0 marks: No relevant content

Indicative content:

Analysis of data:

• CO₂ increased from approximately 315 ppm (1960) to 415 ppm (2020)
• Increase of 100 ppm / approximately 30% increase
• Steady upward trend over 60 years
• Small oscillations (seasonal variation due to plant growth/decay)
• Rate of increase appears to be accelerating

Causes of increase:

• Combustion of fossil fuels (coal, oil, gas) for energy
• Deforestation reduces CO₂ absorption by photosynthesis
• Increased agriculture (livestock produce methane, rice paddies)
• Increased industrial activity and transport
• Growing human population increases demand

Effects on ecosystems:

• CO₂ is a greenhouse gas that traps heat radiation
• Causes global warming / enhanced greenhouse effect
• Rising temperatures affect habitats
• Melting polar ice reduces habitat for polar species (bears, seals, penguins)
• Rising sea levels flood coastal ecosystems / salt marshes
• Changing weather patterns (more droughts / floods)
• Ocean acidification (CO₂ dissolves forming carbonic acid)

Impact on biodiversity:

• Species distribution changes (species move to cooler areas / higher altitudes)
• Some species cannot adapt / migrate fast enough
• Increased extinction risk for specialist species
• Coral bleaching due to warmer oceans (symbiotic algae die)
• Changes in migration patterns / breeding seasons
• Invasive species spread to new areas
• Loss of biodiversity reduces ecosystem stability
• Disruption of food chains / webs

Evaluation:

• Some species may benefit (longer growing seasons in some regions)
• But overall negative impact on biodiversity
• Rate of change is too fast for many species to adapt
• Interconnected ecosystems mean effects cascade
• Urgent action needed to reduce emissions

Question 8: 9 marks

Level 3 (7-9 marks): A comprehensive evaluation that includes:

• Clear explanation of insulin's role in controlling blood glucose
• Detailed comparison of all three methods with multiple advantages and disadvantages
• Consideration of medical factors (effectiveness, side effects, quality of life)
• Consideration of economic factors (cost, cost-effectiveness over time)
• Evaluation leading to a justified conclusion
• Logical structure and specialist terminology used accurately throughout

Level 2 (4-6 marks): A reasonable evaluation that includes:

• Basic explanation of insulin's role
• Comparison of at least two methods with some advantages and disadvantages
• Some consideration of medical or economic factors
• Limited evaluation
• Some use of specialist terminology, generally accurate

Level 1 (1-3 marks): A limited evaluation that includes:

• Simple statement about insulin and blood glucose
• Simple description of one or more methods
• Little comparison or evaluation
• Limited use of specialist terminology

0 marks: No relevant content

Indicative content:

Control of blood glucose:

• Pancreas monitors blood glucose concentration
• High blood glucose triggers insulin release
• Insulin causes glucose to move from blood into cells
• Glucose converted to glycogen in liver/muscles for storage
• Lowers blood glucose back to normal
• In Type 1 diabetes, pancreas doesn't produce enough insulin
• So blood glucose remains high (hyperglycaemia)

Method A - Daily injections: Advantages:

• Cheapest option (£500/year)
• Well-established method
• Patient has control over treatment

Disadvantages:

• Requires multiple daily injections
• Requires regular blood glucose monitoring
• Careful diet and exercise control needed
• Risk of injecting wrong amount
• Doesn't respond automatically to changes in blood glucose

Method B - Insulin pump: Advantages:

• More convenient than injections
• Can be programmed for different times
• Automatic monitoring and adjustment
• Better blood glucose control
• Improved quality of life

Disadvantages:

• More expensive (£2000/year)
• Device must be worn constantly
• Technical failures possible
• Requires training to use
• Still requires monitoring

Method C - Pancreatic cell transplant: Advantages:

• Potential cure (50% don't need insulin after 3 years)
• Natural insulin production restored
• No daily injections or monitoring needed
• Better quality of life if successful

Disadvantages:

• Very expensive (£20,000)
• Only 50% success rate
• Major surgery with risks
• Immunosuppressant drugs needed for life (side effects, increased infection risk)
• Shortage of donor cells
• Rejection possible

Economic evaluation:

• Method A costs £5000 over 10 years
• Method B costs £20,000 over 10 years
• Method C costs £20,000 initially, if successful saves long-term costs
• If unsuccessful, patient still needs Method A or B
• NHS budget constraints mean cost-effectiveness is important

Conclusion (examples):

• Method A is appropriate for most patients (cost-effective, reliable)
• Method B is better for patients who struggle with injections or need better control
• Method C is worth considering for younger patients despite risks (potential long-term benefits)
• Combination of medical and economic factors means different methods suit different patients

Question 9: 9 marks

Level 3 (7-9 marks): A comprehensive discussion that includes:

• Clear explanation of energy loss between trophic levels with specific reasons
• Detailed description of multiple farming methods that increase production
• Evaluation of environmental impacts (positive and/or negative) of multiple methods
• Suggestions for sustainable food production
• Consideration of both efficiency and environmental impact
• Logical structure and specialist terminology used accurately throughout

Level 2 (4-6 marks): A reasonable discussion that includes:

• Some explanation of energy loss in food chains
• Description of some farming methods
• Some description of environmental impacts
• Some mention of sustainability
• Some use of specialist terminology, generally accurate

Level 1 (1-3 marks): A limited discussion that includes:

• Basic statement about energy in food chains
• Simple description of one farming method
• Simple statement about environmental impact
• Little or no evaluation
• Limited use of specialist terminology

0 marks: No relevant content

Indicative content:

Energy loss in food chains:

• Only 10% of energy transferred between trophic levels
• Approximately 90% lost at each stage
• Energy lost through: respiration (heat), movement, excretion, undigested material / egestion
• Not all organism is eaten (e.g., bones, roots)
• This limits length of food chains
• Means eating plants is more energy-efficient than eating animals

Methods to increase food production:

Fertilisers:

• Replace minerals / nutrients in soil (nitrogen, phosphorus, potassium)
• Increase plant growth / biomass
• Increase crop yield

Pesticides:

• Kill pests (insects, weeds, fungi) that damage crops / compete with crops
• Reduce crop loss
• Increase yield

Keeping animals indoors:

• Reduces energy loss through movement
• Temperature controlled so less energy lost as heat / maintaining body temperature
• More energy transferred to growth / biomass
• Animals reach market weight faster

Antibiotics:

• Prevent disease in animals
• Animals grow faster / don't lose energy fighting infection
• Reduce mortality

Genetic modification:

• Crops resistant to pests / herbicides / diseases
• Crops with higher yields
• Crops that grow in difficult conditions

Environmental impacts:

Fertilisers:

• Eutrophication if fertilisers leach into waterways
• Algal bloom blocks light
• Plants die, bacteria decompose them using oxygen
• Fish and other organisms die from lack of oxygen
• Reduces biodiversity

Pesticides:

• Kill non-target species
• Bioaccumulation in food chains (toxins concentrate at higher trophic levels)
• Harm predators / insectivores
• Reduce biodiversity
• Pests can develop resistance

Indoor farming:

• High energy use for heating / lighting (fossil fuels → CO₂)
• Ethical concerns about animal welfare
• But: more efficient land use

Antibiotics:

• Antibiotic resistance develops in bacteria
• Can transfer to human pathogens
• Makes treating human diseases more difficult

Deforestation for agriculture:

• Habitat loss reduces biodiversity
• Reduces CO₂ absorption (climate change)
• Soil erosion

Monoculture:

• Single crop reduces biodiversity
• Increases pest vulnerability
• Soil depletion

Sustainable approaches:

• Biological pest control (use predators instead of chemicals)
• Crop rotation maintains soil nutrients
• Organic farming (no artificial chemicals)
• Reduce food waste
• Eat less meat / shorter food chains
• Use renewable energy for heating
• Balance food production with environmental protection
• Integrated approach combining methods

Sample Answers with Examiner Commentary

Question 6 — Sample Answers

Grade 9 (top of Higher) answer

Enzymes are biological catalysts that speed up metabolic reactions. They are proteins with a specific three-dimensional shape, including an active site that is complementary to the substrate. When the substrate binds to the active site, an enzyme-substrate complex forms. This lowers the activation energy needed for the reaction. Once products are formed, they are released and the enzyme can be reused. This is described by the lock and key model, though the induced fit model suggests the active site changes shape slightly when the substrate binds.

The results in Table 6.1 show that amylase has an optimum pH of 7, where starch is broken down fastest (in 60 seconds). This makes sense because amylase works in the mouth (saliva) and small intestine where pH is around neutral. At pH 6 and pH 8, the enzyme still works but less efficiently (90s and 75s), showing it can tolerate slight pH changes. However, at extreme pH values like pH 4 (420s) and pH 10 (360s), the enzyme works much more slowly.

pH affects enzyme activity because changes in pH alter the charges on the amino acids in the enzyme's structure. Extreme pH breaks the hydrogen and ionic bonds that maintain the enzyme's tertiary structure. This changes the shape of the active site so it is no longer complementary to the substrate. The enzyme is denatured. At pH 4, the enzyme is denatured by excess H⁺ ions, while at pH 10, excess OH⁻ ions cause denaturation. This is irreversible, which is why the rate remains slow even after extended time. At pH values closer to the optimum, the active site is only slightly altered, so some enzyme activity remains.

Temperature also affects enzyme activity. As temperature increases, molecules have more kinetic energy so there are more frequent collisions between enzyme and substrate. This increases the rate of reaction. However, above the optimum temperature (usually around 37°C for human enzymes, but higher for industrial enzymes), the enzyme denatures because increased vibration breaks bonds in the enzyme structure. Substrate concentration also affects rate - if substrate concentration is low, there are fewer enzyme-substrate collisions so the rate is slower. However, once all active sites are occupied, increasing substrate concentration further has no effect.

In industrial applications, enzymes from bacteria have several advantages. Bacterial amylase can be produced in large quantities in fermenters and bacteria can be genetically modified to produce more enzyme or to work at different temperatures. Industrial enzymes often have higher optimum temperatures (60-70°C) which makes them useful in biological washing powders as they work well at washing machine temperatures and denature stains like proteins faster. Using enzymes in washing powder means clothes can be washed at lower temperatures, saving energy and reducing costs. However, some people are allergic to enzymes in washing powder. In food production, amylase is used to break down starch to sugar in bread making and brewing. The advantages are that enzymes are specific so they only catalyse desired reactions, they work at relatively low temperatures and neutral pH so are cheaper than chemical catalysts, and they are biodegradable so more environmentally friendly.

Mark: 9/9

Examiner commentary: This is an exemplary answer demonstrating comprehensive understanding across all assessment objectives. The candidate provides detailed explanation of enzyme structure and function with accurate terminology (complementary, enzyme-substrate complex, activation energy, induced fit). The analysis of Table 6.1 is thorough with specific reference to multiple data points and identification of the optimum pH with scientific reasoning. The explanation of pH effects includes the molecular mechanism of denaturation. Discussion of temperature and substrate concentration is detailed and accurate. The evaluation of industrial applications is balanced, covering advantages with specific examples and acknowledging limitations. The answer is logically structured with clear progression and demonstrates the ability to link concepts across different areas of biology. Full marks awarded.

Grade 6 (solid pass) answer

Enzymes are proteins that speed up reactions. They have an active site that the substrate fits into, like a lock and key. The substrate binds to the active site and the enzyme breaks it down into products. Then the products leave and the enzyme can be used again.

From Table 6.1, the optimum pH for amylase is pH 7 because this is where the time is shortest (60 seconds), so the reaction is fastest. At pH 6 and 8 the times are a bit longer (90s and 75s) so the enzyme is slower. At pH 4 and pH 10 the enzyme is much slower (420s and 360s) because these pH values denature the enzyme. When an enzyme is denatured, the active site changes shape so the substrate doesn't fit anymore. This happens because extreme pH breaks the bonds in the enzyme.

Temperature affects enzymes too. When temperature increases, the particles move faster so there are more collisions and the reaction goes faster. But if the temperature gets too high, the enzyme denatures and stops working. This is permanent. Human enzymes work best at 37°C because that is body temperature. Amylase is found in saliva and the pancreas, which is why it works best at pH 7.

Enzymes are used in industry because they are useful. In washing powders, enzymes like proteases break down protein stains and lipases break down fat stains. This is good because you can wash clothes at lower temperatures which saves electricity and money. Bacterial enzymes are better for industry because they can work at higher temperatures than human enzymes. Scientists can also genetically modify bacteria to make lots of enzyme. In food production, amylase breaks starch into sugar which is used in brewing and making bread.

However, there are some problems with using enzymes. Some people are allergic to them. Also if the temperature is too high the enzyme stops working. Enzymes are more environmentally friendly than chemicals because they break down naturally.

Mark: 6/9

Examiner commentary: This is a solid mid-level response that demonstrates good understanding of the key concepts. The candidate correctly explains basic enzyme function using the lock and key model and provides adequate analysis of the data, identifying the optimum pH and comparing values. The explanation of denaturation is present but lacks the molecular detail of a top answer (doesn't specify hydrogen/ionic bonds or changes in charges on amino acids). Temperature effects are described correctly but without mentioning kinetic energy explicitly or discussing substrate concentration effects. The industrial applications section covers relevant points but lacks depth in evaluation - advantages are listed but not fully developed, and the discussion of limitations is brief. To reach Level 3, the answer would need more detailed scientific explanation of pH effects, discussion of other factors like substrate concentration, and more thorough evaluation of industrial uses with specific examples and balanced consideration of advantages and disadvantages.

Grade 3 (near miss) answer

Enzymes speed up reactions in the body. They are made of proteins and have an active site. The substrate goes in the active site and gets broken down. The enzyme is not used up so it can be used again.

The table shows that pH 7 is the best because it takes 60 seconds. pH 4 and pH 10 are the worst because they take over 400 seconds. This is because the pH is too high or too low and the enzyme doesn't work properly. If the pH is wrong the enzyme will denature and die.

Temperature is important for enzymes. If it is too cold the enzyme works slowly. If it is too hot the enzyme denatures and dies. The best temperature for enzymes is 37 degrees.

Enzymes are used in washing powder to clean stains. This is better than using chemicals because enzymes are natural. Bacteria make enzymes that can be used in factories. GM bacteria can make more enzymes. Amylase breaks down starch into glucose. This is used in food.

Mark: 3/9

Examiner commentary: This answer demonstrates limited understanding and just reaches the bottom of Level 1. The candidate shows basic knowledge that enzymes are proteins with active sites and can catalyse reactions, and correctly identifies that pH 7 is optimal from the data. However, there are significant issues: the explanation of enzyme function lacks key detail (no mention of complementary shape, enzyme-substrate complex, or how the reaction is catalysed), the phrase "enzyme denatures and dies" shows a common misconception (enzymes are not alive), and there is no explanation of why pH or temperature affect enzyme activity. The reference to data is minimal and superficial. The industrial applications section lists some relevant points but without explanation or evaluation. To improve, the candidate should: explain that enzymes are specific because of the complementary shape between active site and substrate; analyse the data more thoroughly by comparing multiple values and explaining trends; explain that pH changes the shape of the active site by affecting bonds in the enzyme structure (avoiding anthropomorphism like "dies"); discuss how temperature affects kinetic energy and collision frequency; and provide a more detailed evaluation of industrial applications with specific advantages and disadvantages.

Question 8 — Sample Answers

Grade 9 (top of Higher) answer

The pancreas constantly monitors blood glucose concentration. When blood glucose rises after eating, the pancreas releases insulin into the bloodstream. Insulin is a hormone that travels to target organs, particularly the liver and muscles. It causes cells to take up more glucose from the blood and stimulates the liver to convert glucose into glycogen for storage. This lowers blood glucose back to the normal level of around 90 mg/100 cm³. In Type 1 diabetes, the pancreatic cells that produce insulin are destroyed by the person's immune system, so insufficient insulin is produced. This means blood glucose concentration remains dangerously high after eating, which can cause damage to blood vessels, nerves, and organs.

Method A (daily injections) is the most established and cheapest treatment at £500 per year. Patients inject insulin 2-4 times daily to replace the missing hormone. The advantages are that it is cost-effective for the NHS, the technique is well-established with decades of safety data, and patients have direct control over their treatment. However, the disadvantages are significant for quality of life. Patients must inject multiple times daily, which is inconvenient and can be painful. They must monitor blood glucose regularly by finger-prick testing, carefully control their diet and exercise, and time their injections appropriately. There is also a risk of injecting too much insulin (causing hypoglycaemia) or too little (causing hyperglycaemia). The treatment doesn't respond automatically to changing blood glucose levels like a healthy pancreas would.

Method B (insulin pump) costs £2000 per year, so is four times more expensive than Method A. The pump is worn continuously and delivers insulin through a needle under the skin. It can be programmed to deliver different doses at different times and monitors blood glucose automatically using a sensor. The advantages are much better convenience and quality of life - no multiple daily injections, better blood glucose control because the system responds automatically, and reduced risk of dangerous glucose levels. However, the disadvantages include the higher cost, the need to wear a device constantly (which some people find uncomfortable or embarrassing), the possibility of technical failure, and the need for training. For a young patient expected to live 60+ years with diabetes, the extra £1500 per year amounts to £90,000+ over a lifetime.

Method C (pancreatic cell transplant) costs £20,000 as a one-off procedure. Healthy insulin-producing cells from a donor are transplanted into the patient's pancreas. If successful, these cells produce insulin naturally, potentially curing the diabetes. The success rate is 50% after 3 years, meaning half of patients no longer need insulin injections. The advantages are substantial if it works: natural insulin production is restored, no daily injections or monitoring needed, and significantly better quality of life. The patient would save the ongoing costs of Methods A or B. However, there are serious disadvantages: it is very expensive initially, requires major surgery with associated risks (infection, anaesthetic complications), has only a 50% success rate, and requires lifelong immunosuppressant drugs to prevent rejection of the transplanted cells. Immunosuppressants have significant side effects and increase the risk of infections and cancer. There is also a shortage of donor tissue, limiting availability.

From a medical perspective, Method A is adequate for most patients and very safe. Method B offers better glucose control and quality of life, which reduces long-term complications like kidney disease, blindness, and nerve damage - these complications are very expensive to treat. Method C offers the possibility of a cure but with significant risks.

From an economic perspective, Method A appears cheapest, but poor glucose control leads to expensive complications. Method B costs more initially but may save money long-term by preventing complications. Method C is expensive but if successful, saves all future treatment costs. For a young patient diagnosed at age 20 and living to 80, Method A would cost £30,000, Method B would cost £120,000, while successful Method C costs £20,000 total. However, if Method C fails, the patient needs Method A or B anyway, plus they've had surgery and take immunosuppressants.

In conclusion, I believe Method A is appropriate for most newly-diagnosed patients as it is cost-effective and safe, while patients learn to manage their condition. Method B should be offered to patients who struggle with injections or experience poor glucose control with Method A, as the improved control justifies the higher cost by preventing expensive complications. Method C should be considered for young, otherwise healthy patients who find the daily management very difficult, but only after careful discussion of the risks and the 50% failure rate. The decision should be individualised based on the patient's age, other health conditions, personal circumstances, and preferences, balancing medical effectiveness, quality of life, and cost.

Mark: 9/9

Examiner commentary: This is an outstanding answer that fully addresses all aspects of the question at the highest level. The candidate provides a detailed and accurate explanation of how insulin controls blood glucose, including the specific mechanisms (glycogen