Protecting Our Cells

Overview

Students learn that a cell is a tiny building block of living things and that cells can be damaged by chemical changes such as oxidation. They investigate how a teacher-prepared, water-based kawakawa (kawakawa) infusion and a control affect apple browning as an observable model of oxidation. Students consider that an antioxidant is a substance that can slow or reduce oxidation, while recognising that reduced apple browning does not prove antioxidant effects in human cells or health benefits.

The lesson introduces rongoā Māori respectfully: this knowledge is taonga, pronunciation and local guidance matter, and mana whenua, kaumātua or another trusted local source should be involved where appropriate. Students observe, compare, record and communicate evidence without presenting the activity as proving medicinal effectiveness. Apple browning is not a direct measurement of antioxidant concentration, protection of human cells or health benefit.

Learning intentions

• WALT define a cell as a tiny building block of living things.
• WALT identify that cells need protection from damage.
• WALT explain that oxidation is a chemical change that can damage materials and cells.
• WALT define an antioxidant as a substance that can slow or reduce oxidation.
• WALT investigate apple browning as an observable model of oxidation and compare a kawakawa infusion with control water.
• WALT use evidence to explain what the investigation can and cannot show: observing reduced apple browning is not proof of antioxidant effects in human cells.
• WALT learn about kawakawa and rongoā Māori respectfully, recognising that rongoā knowledge is taonga and that this investigation does not test medicinal effectiveness.

Success criteria

• I can explain that a cell is a tiny building block of a living thing and that cells can be damaged.
• I can explain that oxidation is a chemical change that can cause a cut apple to brown and can damage materials or cells.
• I can define an antioxidant as a substance that can slow or reduce oxidation.
• I can compare the kawakawa infusion with the control using observations at 0, 5 and 10 minutes.
• I can record evidence and explain whether the test was fair by identifying the variable and controls.
• I can explain that less apple browning may be evidence of less oxidation in the apple model, but does not prove an effect in human cells, medicinal effectiveness or health benefit.
• I can speak about kawakawa and rongoā Māori respectfully, including using the correct pronunciation taught by a trusted local guide.

Curriculum links

• New Zealand Curriculum, Science, Biological Science, Phase 1 (Years 0–3): living things and their relationships, including how plants are part of living systems and are valued by people.
• Science practices: observing, comparing, recording and communicating evidence from a simple investigation.
• New Zealand Curriculum Online, Science Phase 1 (Years 0–3): https://newzealandcurriculum.tahurangi.education.govt.nz/new-zealand-curriculum-online/nzc---science-phase-1-years-0-3/5637292339.p

Key vocabulary

• cell — a tiny building block of a living thing
• oxidation — a chemical change that can cause browning or damage materials and cells
• antioxidant — a substance that can slow or reduce oxidation
• evidence — observations or information that help us answer a question
• control — the comparison condition used to help make a test fair
• variable — something that can change in an investigation
• model — a simplified way to study or explain something

Rongoā Māori, taonga, kawakawa, browning, infusion, fair test, observe, compare, record.

Prior knowledge

Students should know that plants are living things and that people value and use plants in different ways. Introduce kawakawa with guidance from mana whenua, a kaumātua or another trusted local source where appropriate. Explain that rongoā Māori knowledge is taonga, local practices vary, and the correct pronunciation should be learned and used respectfully. Seek permission before collecting any plant material; for this lesson, the teacher should source or prepare material appropriately rather than asking students to collect it. Invite whānau knowledge without asking students to disclose private health information or treating cultural knowledge as a testable medical claim.

Lesson structure (45 minutes)

1. 0–6 min · Respectful introduction and hook. Show a cut apple and introduce kawakawa using the correct pronunciation provided by a trusted local guide. Explain that a cell is a tiny building block of living things and that cells need protection from damage. Explain that rongoā Māori knowledge is taonga and that the class will learn respectfully, without claiming to test or prove medicinal effectiveness. Show the learning intentions and ask students to predict what may happen to apple pieces over time.

2. 6–12 min · Explicit teaching and teacher explanation. Use the analogy: “Cells are like tiny rooms that make up a living thing. Oxidation is a chemical change—like when a cut apple’s inside reacts with the air and browns. An antioxidant is a substance that can slow or reduce oxidation.” Explain that the apple is a model for studying visible browning, not a human cell. Introduce evidence as observations that help answer a question and a control as the comparison condition that helps make a test fair. Explain that reduced apple browning could be evidence of less oxidation in the apple model, but cannot prove an antioxidant effect in human cells. Clarify the independent variable (kawakawa infusion or control water), dependent variable (visible apple colour change), and controls: identical apple pieces, equal drops, the same plates, timing, room conditions and observation method.

3. 12–27 min · Safe observation investigation. Before handling materials, wash hands, check allergies and follow school food-safety policies. The teacher prepares and labels a water-based kawakawa infusion and control water; students do not collect, prepare, taste or claim to consume either sample. Using clean equipment, students place equal drops of each liquid on equal-sized, identical apple pieces, with a plain untreated piece if time and materials allow. Record colour at 0, 5 and 10 minutes in a table using “I notice…” statements. Add prompts: “What is your evidence?” “What changed?” “How might browning show oxidation?” “What is the control?” and “What can this apple model not tell us about human cells?” Keep samples separate, do not taste them, and dispose of them hygienically. Emphasise that any difference in browning does not prove medicinal effectiveness, antioxidant effects in human cells, antioxidant concentration or health benefit.

4. 27–34 min · Compare, formative check and communicate. In groups, students compare the kawakawa and control observations, identify patterns and discuss whether the test was fair. Use a quick formative check: students show thumbs up/down or complete orally, “The control helps us compare fairly because ___,” “Apple browning is evidence of ___ in this model,” and “This does/does not prove an effect in human cells because ___.” Students distinguish observations from inferences and suggest one improvement, such as using more identical pieces or repeating the test.

5. 34–40 min · Cultural and scientific discussion. Ask: “What did we observe?” “How were the treatments controlled?” “Why is apple browning only a model of oxidation?” “What might an antioxidant do?” “Why can’t this investigation prove protection of human cells?” and “How can we learn about rongoā respectfully?” Reinforce that permission, local guidance and correct pronunciation matter, and that scientific classroom observations do not replace rongoā knowledge or demonstrate health effects.

6. 40–45 min · Conclusion and exit ticket. Students complete: “The kawakawa infusion and control…”, “One observation at ___ minutes was…”, “A fair-test control was…”, “Apple browning may show ___ in our apple model, but it cannot prove ___ in human cells,” and “An antioxidant is…”. Invite a few students to share evidence-based answers and collect responses.

Resources

• Teacher-prepared, labelled water-based kawakawa infusion, sourced with appropriate local guidance
• Labelled control water
• Identical apple pieces, prepared by the teacher on a clean board
• Droppers or pipettes, measuring guide, clean plates and timer
• Observation table and exit-ticket worksheet
• Handwashing supplies, gloves or tongs for teacher handling, and rubbish/compost container
• Information or pronunciation guidance from mana whenua, a kaumātua or another trusted local source where appropriate
• Local guidance on permission, collection and use of kawakawa; do not collect without permission
• Pencils and group recording materials
• Allergy, sensory, dietary and health information

Assessment

• Check whether students can define a cell as a tiny building block of living things and explain that cells need protection from damage.
• Listen for accurate explanations that oxidation is a chemical change that can cause apple browning and may damage materials or cells, and that an antioxidant can slow or reduce oxidation.
• Check whether students accurately record colour observations at 0, 5 and 10 minutes and compare the kawakawa infusion with the control.
• Listen for correct identification of the independent variable, dependent variable and fair-test controls.
• Use the formative check and exit ticket to assess whether students distinguish observations from inferences and use evidence to explain that reduced apple browning is evidence within an apple model, not proof of antioxidant effects in human cells, medicinal effectiveness or health benefit.
• Check that students communicate the purpose and limits of the model and understand that rongoā Māori knowledge is taonga and the investigation does not prove medicinal effectiveness.

Differentiation

• Provide a picture vocabulary mat, colour cards, a partially completed observation table and sentence starters such as “At 5 minutes I notice…” and “The control was fair because…”.
• Model the correct pronunciation supplied by local guidance and allow bilingual or home-language discussion; do not require students to share private whānau or cultural knowledge.
• Offer teacher-demonstrated samples, photographs or a non-handling role for students with allergies, sensory needs or other accommodations. No student tastes samples; follow hygiene, allergy and school safety procedures.
• Support learners to compare only one feature at a time, while extending others to identify possible sources of variation and propose a repeat.

Extension

• Compare the kawakawa infusion with another locally appropriate rongoā plant only after receiving cultural permission and guidance from mana whenua, a kaumātua or another trusted local source. The teacher prepares and labels the material; students do not collect or taste it.
• Students predict, repeat or graph the colour observations while explaining that the result remains an apple-browning proxy and cannot establish medicinal effectiveness, antioxidant concentration or health benefit.