Lesson 7: Photosynthesis Reactions | BIO 2.4

Lesson at a Glance | He Tirohanga Whakamua

Do NowWhere does the oxygen gas we breathe actually come from?10 min

Dual-Phase ModelThylakoid photolysis and stroma carbon fixation15 min

Exercise-book SynthesisComplete Section 7: Photosynthesis Reaction Map10 min

Core Concept CheckTrace inputs & outputs of thylakoid vs stroma5 min

Harakeke ApplicationTest a bounded biological consequence alongside sourced tikanga15 min

Ngā Whāinga Ako | Learning Intentions

Students will know

The balanced chemical equation for photosynthesis: $6 {CO}_{2} + 6 H_{2} O \to C_{6} H_{12} O_{6} + 6 O_{2}$ .
The location and biochemistry of Phase 1: Light-Dependent Reaction inside the thylakoids/grana (light splits $H_{2} O$ via photolysis, releasing $O_{2}$ gas and generating ATP + NADPH).
The location and biochemistry of Phase 2: Light-Independent Reaction (Calvin Cycle) inside the stroma (uses ATP + NADPH to fix ${CO}_{2}$ into glucose).

Students will demonstrate

By drawing a complete dual-phase chloroplast reaction schematic.
By completing formative Section 7 in their class exercise book or revision folder.

Curriculum alignment

NZC (2007) · Science · Level 7 · Living World: “Explore the diverse ways in which animals and plants carry out the life processes.”

Do Now | Tīmatanga Whakaaro (10 min)

Photolysis Prompt:

"When a plant releases oxygen gas, does that oxygen come from the ${CO}_{2}$ gas it takes in, or from the $H_{2} O$ water it absorbs from the soil?"

Unpack: Heavy isotope tracking proves all released $O_{2}$ gas comes directly from photolysis of $H_{2} O$ in the thylakoid membranes! Light energy splits water molecules ( $2 H_{2} O \to 4 H^{+} + 4 e^{-} + O_{2}$ ), releasing oxygen gas as a byproduct while capturing hydrogen for the Calvin cycle.

Dual-Phase Chloroplast Reactions (15 min)

🍃 Phase 1: Light-Dependent (Thylakoids / Grana)

Location: Thylakoid membranes (grana).
Inputs: Light energy, $H_{2} O$ , ${NADP}^{+}$ , ADP + $P_{i}$ .
Process: Chlorophyll absorbs light; photolysis splits $H_{2} O$ .
Outputs: $O_{2}$ gas (released), ATP, NADPH.

🧪 Phase 2: Light-Independent / Calvin Cycle (Stroma)

Location: Fluid stroma of chloroplast.
Inputs: ${CO}_{2}$ gas, ATP, NADPH (from Phase 1).
Process: RuBisCO enzyme fixes ${CO}_{2}$ into 3-carbon sugars.
Outputs: Glucose ( $C_{6} H_{12} O_{6}$ ), ${NADP}^{+}$ , ADP.

📁 Formative Revision Exercise Book — Section 7: Photosynthesis Reaction Map

Students complete Section 7 in their exercise book or class revision folder. This is formative classroom evidence, not an NZQA submission:

Section 7 Requirements:

1. Annotated Chloroplast Diagram: Draw a double-membrane chloroplast showing Grana stacks, Thylakoid membranes, and Stroma with inputs/outputs marked.

2. Phase 1 vs Phase 2 Comparison Matrix: Detailed table listing location, energy source, primary inputs, primary outputs, and the key components taught above (including chlorophyll and RuBisCO).

3. Excellence Limiting Factors Analysis: 1-paragraph explanation of how low temperature or low ${CO}_{2}$ limits the Calvin cycle enzyme (RuBisCO) rate regardless of light intensity.

Core Concept Check | Tirohia te Māramatanga (5 min)

Exit Check:

"My Section 7 diagram shows photolysis of H₂O occurring in the thylakoids releasing O₂, while CO₂ fixation into glucose occurs in the stroma."

Te Pā Harakeke: a bounded biological application alongside tikanga (15 min)

You have just traced where photosynthesis occurs. Apply that biology carefully alongside two named sources, without turning it into the origin or authority for tikanga.

What the sources establish. Te Papa's harakeke teaching resource explains that whakapapa informs harvesting practice: the rito and the two leaves protecting it are not harvested, while outer leaves are taken. Manaaki Whenua's pā harakeke guidance likewise says never to harvest the central three leaves and directs kaiako to local weavers for local tikanga.

A necessary qualification about offcuts. Manaaki Whenua records that old leaves and weaving scraps were traditionally placed beneath the parent bush, but its current maintenance guidance recommends keeping dead material and debris clear where it can harbour leaf-chewing insects. Do not turn either practice into a universal rule: follow the people who hold and tend the local pā harakeke.

The task (in pairs). Using only what you worked out this lesson about where photosynthesis happens and what limits its rate:

Predict one possible effect on future photosynthetic capacity if the protected central growth fan is damaged. Label your answer as a biological prediction, not the reason for the tikanga.
Compare the likely contribution of mature outer leaves and the protected central growth to present and future leaf area. State what further observations you would need before claiming a net effect.
Trace the carbon in a removed leaf. Compare what may happen if plant material decomposes on site with what may happen if debris is cleared; include both nutrient cycling and pest-management considerations.

Then discuss. The biology offers one bounded way to investigate possible consequences of damage to leaf area and new growth. It does not establish why the tikanga exists, what it means, or who has authority to interpret it. Those questions remain with the people who hold the practice.

Kaiako — mātauranga handoff. The activity structure above is ours to run. The authoritative account of harakeke tikanga — including which practices are shared freely, which are iwi- or hapū-specific, and the meaning of mauri in this context — belongs with kaiako Māori, local weavers and kaumātua. Please invite that verification before teaching, and defer to local practice over anything written here. Do not present the biology as the reason for the tikanga.

Teacher Planning & NCEA Alignment

NCEA Level 2 Biology Alignment (4 Credits External):

Photosynthesis: Demonstrate understanding of chloroplast structure, light-dependent reactions, Calvin cycle, and environmental factors affecting rates.
Organelle Adaptations: Explain how stacked thylakoids maximise light absorption surface area.

Vocabulary: Photosynthesis, chloroplast, thylakoid, grana, stroma, photolysis, light-dependent phase, light-independent phase, Calvin cycle, RuBisCO, NADPH, ATP.

Paired concept in Guided Media & Evidence: photosynthesis reactions →

Lesson 7: Photosynthesis: Light-Dependent & Light-Independent Reactions