Show model answer and explanation
breathing
Breathing is mechanical air movement.
Class 8 · English Medium · Pearson Edexcel · General science
Pearson iLowerSecondary Science sample overview · Chapter companion part
Year 8 · Respiration, evidence and respiratory health
Separate breathing from respiration, interpret supplied air data, and explain how smoke can harm gas transport and exchange.
Selected Pearson Year 8 biology companion, mapped to the public sample overview. It is placed in the Class 8 Edexcel pathway for access; confirm your school programme year with a teacher. This does not establish equivalence with a national school class or complete programme coverage.
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Learn the idea
Respiration is a set of chemical processes that transfers energy from nutrients for cell activities. Aerobic respiration uses oxygen. Breathing is movement of air into and out of the lungs; it supplies oxygen and removes some carbon dioxide, but the mechanical movement is not the same process as respiration in cells.
A useful word model
In the aerobic model, glucose reacts with oxygen, forming carbon dioxide and water while energy is transferred for cell activities and to the surroundings. Energy is released, not created from nothing. This word description is sufficient here; balancing symbol equations and detailed ATP chemistry belong to further study, not to these Year 8 sample objectives.
Plants respire too
Living plant cells need energy for activities and respire during the day and night. Photosynthesis uses light energy in suitable cells to make sugars; it does not replace respiration. Roots and other non-green tissues can respire without photosynthesising. Do not conclude that a plant is only respiring when it is dark.
Air is a mixture before and after breathing
Exhaled air still contains oxygen as well as carbon dioxide, nitrogen and other gases. Compare supplied data rather than saying every oxygen molecule is used. In a fictional rounded table, 100 equal units of inhaled air contain 21 units of oxygen and an exhaled sample contains 16. The difference is 5 units out of 100, not a personal test result.
How smoke can cause harm
Tobacco smoke can irritate and damage airways and lung tissue. Cilia are tiny moving hair-like structures lining airways. Damage to them reduces clearance of mucus and trapped particles; damage to exchange surfaces can reduce effective gas exchange. Carbon monoxide reduces the capacity of blood to carry oxygen. Different smoke components have different effects, so a single vague statement about dirty lungs is not a complete explanation.
Interpret evidence honestly
Supplied tables are practice models, not measurements of classmates. A change in breathing rate can have several causes and does not by itself diagnose illness or rank fitness. Compare the same duration and conditions, consider repeated observations, and state what information is missing. Never create a smoke exposure, collect personal medical histories or perform a breath-holding challenge for this lesson.
Connect demand and supply
Active cells can require faster energy transfer, so oxygen supply and carbon dioxide removal may need to increase. Breathing rate is the number of breaths per stated time; cellular respiration rate is a chemical-process rate. One can affect the other without being the same quantity. For a fictional rate of 18 breaths per minute held for two minutes, the model predicts 36 breaths.
Write a careful explanation
Use the chain: named change → effect on structure or transport → consequence for cells. For example, reduced oxygen-carrying capacity can limit oxygen supply for aerobic respiration. The lesson is biological education, not a diagnosis or personal treatment plan. Discuss real concerns with a guardian and an appropriate qualified professional; practise here with supplied fictional data only.
Worked example
A model air table has oxygen values of 21 and 16 equal parts per 100. Subtract 21 − 16 = 5 fewer parts per 100 in the supplied exhaled sample. This shows a difference in the model samples, not that all inhaled oxygen has disappeared or that a person has a particular condition.
- Identify the structure or process before naming its function.
- Use the supplied evidence and explain the link; a label alone is not an explanation.
- Compare your response with the model, then improve one part of your reasoning.
Common mistake
Carbon dioxide is a respiration product; carbon monoxide is a different gas that can impair oxygen carriage. Similar names do not mean the same function.
A rate calculation
A fictional table gives 45 breaths in three minutes. Dividing by three gives 15 breaths each minute in that model; it is not a health threshold.
An evidence limit
A model with fewer working exchange surfaces predicts reduced exchange area. It cannot identify the cause of a real person’s symptoms or prescribe a treatment.
Your written practice
Show your working on paper and enter your answer here. If it does not match, compare the model and try again.
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respiration
Respiration occurs in living cells; it is not simply chest movement.
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glucose
Glucose reacts with oxygen in the model.
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oxygen
Aerobic means the process uses oxygen.
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carbon dioxide
Carbon dioxide and water form while energy is transferred.
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water
Water is a material product; released energy is not a substance.
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carbon monoxide
Carbon monoxide interferes with oxygen carriage in blood.
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5
21 − 16 = 5 fewer oxygen units in each 100-unit model sample.
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36
18 × 2 = 36 breaths; the calculation does not diagnose a person.
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12
24 ÷ 2 = 12 breaths per minute in this fictional model.
Write in your own words. A guardian or teacher should review this response.
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Breathing moves air and supports gas supply; respiration is chemical energy transfer in cells. Blood transport links the lungs and other tissues.
Give different processes and locations, plus their relationship.
Write in your own words. A guardian or teacher should review this response.
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Plants respire by day and night. In suitable light, photosynthesis can occur as well; it does not switch respiration off.
State when respiration occurs and distinguish the purpose of photosynthesis.
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Glucose reacts with oxygen to form carbon dioxide and water; stored chemical energy is transferred for cell activities and to surroundings.
Identify reactants and products and describe energy transfer rather than energy creation.
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The exhaled model still contains 16 oxygen units per 100, alongside other gases, so oxygen remains and the air is a mixture.
Use the supplied values, and do not present rounded practice values as every person’s measurements.
Write in your own words. A guardian or teacher should review this response.
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Cilia help move mucus and trapped particles away; damage can reduce this clearance and leave more material in airways.
Connect the structure with its clearance role, rather than saying cilia carry oxygen in blood.
Write in your own words. A guardian or teacher should review this response.
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Exchange-surface damage can reduce effective gas transfer; reduced blood oxygen carriage limits transport after exchange. Both can affect oxygen supply but at different stages.
Distinguish exchange from transport and connect them to cell supply.
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Rates depend on activity, timing, conditions and individual differences. More information and appropriate assessment are needed; the table alone cannot diagnose or rank health.
Explain alternative influences and the limit of the evidence.
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Reduced oxygen carriage can reduce delivery to cells; oxygen is needed for aerobic respiration, so the capacity for aerobic energy transfer may be limited.
Use a cautious causal chain without making a diagnosis or claiming every cell immediately stops working.
Write in your own words. A guardian or teacher should review this response.
Show model answer and explanation
Smoke can cause harm and exposure is unnecessary. Compare supplied fictional diagrams or existing anonymised study summaries with teacher guidance instead.
Reject deliberate exposure and propose an activity that still investigates the scientific idea.
Write in your own words. A guardian or teacher should review this response.
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Use the same duration and activity conditions, repeat observations and compare the results. State that the measurements do not diagnose anyone.
Make the comparison fair and acknowledge variation; use supplied data here rather than testing classmates.
Science notebook challenge
Create a two-column breathing/respiration comparison, explain the supplied 100-unit air table, and draw one smoke-effect chain with a clear limit on what your model proves.
Review with a guardian or teacher
- Keep air movement, gas exchange, blood transport and cellular respiration separate.
- Show each arithmetic step with the stated sample size or time unit.
- Explain one structural effect and one evidence limit without personal diagnosis or exposure.
Keep your work on paper or in a local file. This page does not upload it or automatically grade the project.
Curriculum companion and further study
This original Kidemy practice is mapped to selected Year 8 objectives in the Pearson iLowerSecondary Science sample overview, PDF page 2. This public source does not establish the full programme or a complete textbook chapter list.
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