These GCE A Level Biology 2016 spec topics consistently produce the lowest scores. Prioritise these in your revision.
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Enzyme denaturation — naming bonds broken and active site consequences
In AS 1 2025, many candidates knew the active site changes shape but were 'unsure of how this happens'. The specific A-level mark for naming bonds broken (hydrogen bonds, ionic bonds) and stating the active site is 'no longer complementary' was consistently missed. This pattern appeared in both the written papers and practical unit enzyme conclusions.
Affects: AS 1, AS 3
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Water potential and osmosis — specifying direction and using correct terminology
In AS 1 2023, many candidates could describe plasmolysed cells and use AS terminology for water movement. However, in AS 3 2025, many lost marks on osmosis graph questions by joining points instead of drawing a line of best fit, or by failing to convert sucrose concentration from the x-axis into solute potential. Stating water/solute potential correctly after the practical remains an essential mark point.
Affects: AS 1, AS 3
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Data analysis and trend description in unfamiliar contexts
Examiners in both 2023 and 2025 noted that candidates performed better on recall questions than on data-analysis questions set in unfamiliar scenarios. In AS 1 2023, many identified only one trend in a three-mark table question. In A2 2 2023, a significant number did not refer to the y-axis variable at all when describing muscle-contraction data.
Affects: AS 1, AS 2, A2 1, A2 2
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Ecology questions — comparative language, nitrogen fixation, mycorrhizal associations
Ecology consistently proved the most discriminating section on A2 1. In 2023, only a minority of candidates could explain why nitrogen fixation benefits plants in coastal grasslands. In 2025, many candidates scored only half the marks on ecology comparisons because they omitted comparative terms. Many also struggled to link reduced transpiration to stomatal closure in AS 2 2025.
Affects: AS 2, A2 1
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Statistics — t-test degrees of freedom, p-values, and confidence limits
In A2 2 2025, many candidates struggled with the t-test, particularly calculating degrees of freedom and interpreting p-values. Few recognised that a very low p-value indicated a highly significant difference. In A2 3 2025, Part (iii) of confidence-limit questions was consistently poorly answered, suggesting centres need to emphasise what statistical outputs actually mean for biological conclusions.
Affects: A2 2, A2 3
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Gene technology — reverse transcriptase, restriction enzymes, and transformation markers
In A2 2 2023, 'looseness in terminology' for reverse transcriptase answers penalised many candidates. Only a minority linked pancreatic cells to mature mRNA as the source for cDNA production. In restriction enzyme questions, few candidates could describe how fragment sizes could be determined (running fragments of known length alongside) — DNA probes was the most common but incorrect response.
Affects: A2 2, A2 3
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Photosynthesis — antenna complex, electron acceptors, and limiting factors
In A2 2 2023, the light-dependent reaction question produced a range of responses. Fewer candidates commented that the antenna complex pigments were of different types and could therefore absorb a greater range of wavelengths. A significant number omitted electron acceptors in their account of photosystem excitation. The novel limiting-factors context in Part (c) was handled variably.
Affects: A2 2
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Biological drawings — block diagrams and cell drawings with correct lines and labels
In AS 3 2023, the most common drawing mistakes included completing a block diagram instead of a cell drawing, shading, and failure to produce clear discrete lines. A minority failed to extend label lines to touch the structures and were penalised. In AS 3 2025, block diagram guidance was issued to centres because drawings with sketchy or non-joining lines were being credited incorrectly.
Affects: AS 3, A2 3
