NCEA 91156: life processes at the cellular level (Level 2 Biology)

What NCEA 91156 assesses

NZQA says the life processes in the standard (version 2) are photosynthesis, respiration, and cell division (DNA replication and mitosis as part of the cell cycle) in plant and animal cells. For each, you draw on ideas selected from:

• movement of materials, including diffusion, osmosis and active transport
• enzyme activity (specific enzyme names are not required)
• factors affecting the process
• details of the process only as they relate to the overall functioning of the cell (names of stages are not required)
• reasons for similarities and differences between cells, such as cell size and shape, and the type and number of organelles

The three grades go up in steps. Achieved defines, describes with annotated diagrams or models, and describes characteristics of or gives an account of life processes at the cellular level. Merit uses biological ideas to give reasons how or why life processes occur at the cellular level. Excellence links biological ideas about life processes at the cellular level, which may involve justifying, relating, evaluating, comparing and contrasting, or analysing.

The NCEA 91156 exam in 2026 and 2027

NCEA 91156 is one of three Level 2 Biology externals, with 91157 (genetic variation) and 91159 (gene expression). The 2026 exam is on Friday 20 November, in the morning session. NZQA's specifications for both years say the exam is on printed paper and 91156 is a 4-credit external.

• Three questions: you answer all three. NZQA's 2025 report says each question had bullet points to guide the structure of your answer, and the strongest candidates answered every bullet.
• Question style: you may need to interpret diagrams and new information, draw diagrams, and write responses of one or more paragraphs. Some questions are resource-based, and you may use annotated diagrams as evidence.
• Use the resource and go beyond it: the report says candidates who linked the resource material to their answers did better, and the highest grades added relevant detail that the resource did not give.
• Stay on the question: the report says material that is related to biology but outside what the question asks cannot be credited.
• Extra detail in the specification: photosynthesis includes the light-dependent and light-independent processes; respiration includes anaerobic and aerobic; cell division includes semi-conservative replication, with antiparallel DNA strands and complementary base pairing; movement of materials may include facilitated diffusion; and enzyme factors may include temperature, pH, substrate concentration, co-enzymes, co-factors and inhibitors.

How NCEA 91156 is marked

Three questions, each scored N0 to E8, give a total out of 24. The 2025 paper used photosynthesis, respiration and enzyme activity, and bullet points under each question showed what to cover, so an answer that skips a bullet usually skips a unit of evidence.

NCEA 91156 cut scores

In 2023 Achieved dropped to 6, the lowest of the five years. Excellence has stayed at 19. The scores below are where each grade begins, out of 24.

Cut scores 2025

2025 schedule: Achieved from 7, Merit from 13, Excellence from 19. The same as 2024.

Cut scores 2024

2024 schedule: Achieved from 7, Merit from 13, Excellence from 19. Compared with 2023, Achieved went up by 1.

Cut scores 2023

2023 schedule: Achieved from 6, Merit from 13, Excellence from 19. Compared with 2022, Achieved came down by 1 and Merit came down by 1.

Cut scores 2022

2022 schedule: Achieved from 7, Merit from 14, Excellence from 19. The same as 2021.

Cut scores 2021

2021 schedule: Achieved from 7, Merit from 14, Excellence from 19.

Worked examples at each grade

Achieved: the processes and where they happen

• Photosynthesis, in chloroplasts: carbon dioxide + water → glucose + oxygen, using light energy absorbed by chlorophyll.
• Aerobic respiration, starting in the cytoplasm and finishing in the mitochondria: glucose + oxygen → carbon dioxide + water, releasing energy as ATP.
• Anaerobic respiration, in the cytoplasm: in animal cells glucose → lactate, and in yeast glucose → ethanol + carbon dioxide, releasing much less energy.

Draw an enzyme and its substrate fitting at the active site. NZQA's 2025 report says Not Achieved candidates mixed up photosynthesis and respiration, or placed photosynthesis in the cytoplasm.

Merit: why size and shape matter, and how temperature affects an enzyme

Two cube-shaped cells have sides of 2 µm and 10 µm. The surface area to volume ratio is 6 ÷ side:

The small cell has five times the surface area for every unit of volume, so diffusion of oxygen in and carbon dioxide out reaches the whole cell much faster. The large cell needs a different solution, such as a flattened shape or more organelles.

For enzymes, explain the shape of the temperature graph. At low temperatures the substrate and enzyme have less kinetic energy, so they collide less often and fewer enzyme-substrate complexes form. Near the optimum the collisions are frequent and the rate is highest. Above the optimum, the enzyme's bonds break and its tertiary structure changes, so the active site no longer fits the substrate. The enzyme is denatured and the rate falls to almost zero.

Excellence: linking the processes to a context

A sprinter relies on anaerobic respiration for the first seconds, but a marathon runner depends on aerobic respiration. Compare them. Aerobic respiration needs oxygen and releases far more ATP from each glucose, so it can supply energy for hours, but it is slower to ramp up. Anaerobic respiration releases energy quickly with no oxygen, but gives much less ATP per glucose and produces lactate, which limits how long it can go on. So a sprinter benefits from the speed, and a marathon runner from the yield. Excellence compares and contrasts, uses the context and links the ideas to the energy demand of the cell.

The same approach applies to photosynthesis. On a cold morning, low light and low temperature limit the rate; at midday, light may be plentiful but a closed greenhouse can run short of carbon dioxide, which becomes the limiting factor. Justify which factor limits the rate at each time, and link each to the enzymes in the light-independent reactions.

Now work out a surface area to volume ratio in our Cell Biology course, then press Mark to check your answer in the course:

Exam answers

The answers and a worked mark scheme come with today's paper once it is marked. We do not publish official or past paper answers. Every question on the daily paper is our own.

Use the daily paper as a practice exam

The Level 2 Biology track above is a short timed mock of 8 questions, not a full exam and not written by NZQA (NCEA Level 2 Biology). It covers cell structure, enzymes, membranes and transport, and mitosis and the cell cycle, which support 91156. Photosynthesis and respiration are not topics of their own there, so use our Cell Biology course for those, and it also includes immunity, gas exchange and mass transport, which are not part of 91156. For the whole course, see the NCEA Level 2 Biology guide.

Is NCEA 91156 changing?

The 2027 specification for Level 2 Biology repeats the 2026 detail on photosynthesis stages, respiration types and enzyme factors. Year 12 moves to the NZ Certificate of Education in 2029.

Common mistakes in NCEA 91156

• Mixing up photosynthesis and respiration. NZQA's 2025 report lists this, and giving only a few reactants or products.
• Wrong locations. The report gives the cytoplasm as the site of photosynthesis and stomata as the site of anaerobic respiration as examples.
• Not naming the active site. Label it on the enzyme diagram.
• Writing about things that are not asked. The report says describing inhibitors and co-factors when the question did not ask for them earned no credit.
• Ignoring the resource. Use the information you are given to frame the answer, then add detail beyond it.

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