Edexcel International GCSE (IGCSE) Biology (4BI1) Past Papers 2026

Biology Paper 1

Duration: 2h

Biology Paper 2

Duration: 1h 15m

Enzyme activity — the full temperature/denaturation explanation chain

Across all four reports, partial credit was the norm for enzyme temperature questions. Candidates typically earned one or two marks for stating kinetic energy increases or for naming denaturation, but failed to link all steps: kinetic energy → collision frequency → rate increase (below optimum) AND denaturation → active site shape change → substrate cannot fit (above optimum). The full four-mark chain was frequently incomplete.

Paper 1B 2023, Paper 1B 2024, Paper 2B 2023

Osmosis direction and precise water movement language

In both Paper 1B 2023 (red blood cells in distilled water) and Paper 2B 2024 (cells in preservation solution), a significant number of candidates were confused about the direction of water movement, failed to specify water (not solute) as the substance moving, or incorrectly used 'plasmolysed' for animal cells. The single-mark 'water moves by osmosis' was frequently missed entirely.

Paper 1B 2023, Paper 2B 2024

Menstrual cycle hormones — confusing FSH and LH roles

In Paper 2B 2023 (Q05a) and Paper 2B 2024 (Q04a), candidates consistently confused the roles of FSH and LH. Common errors: stating FSH stimulates ovulation (it is LH); stating LH matures eggs (it is FSH); confusing the hormones with oestrogen and progesterone. The role of LH in stimulating progesterone release was the least well-recalled point.

Paper 2B 2023, Paper 2B 2024

Kidney function — ultrafiltration and ADH/water reabsorption mechanism

Paper 2B 2023 Q03(b)(ii) flagged that candidates described arterial structure rather than explaining the function of the diameter difference in creating ultrafiltration pressure. Paper 2B 2024 Q03(b)(i) noted that weaker answers simply described urine concentration rather than explaining the ADH → collecting duct permeability → water reabsorption chain. Vague terms such as 'water levels in the body' were not credited.

Paper 2B 2023, Paper 2B 2024

Food tests — all four tests, including the emulsion test for lipids

Paper 2B 2024 Q06(a)(ii) assessed the emulsion test for lipids. Common errors: adding ethanol without subsequently adding water; confusing the Sudan III colour (red layer) with other indicators; confusing the lipid test with the protein test. The four food tests (starch/iodine, glucose/Benedict's, protein/Biuret, lipid/emulsion or Sudan III) must all be known with their correct reagents and colour changes.

Paper 2B 2023, Paper 2B 2024

Genetics — using correct allele notation and including phenotypes in Punnett squares

Both 2023 and 2024 Paper 1B reports flagged candidates using different allele letters from those specified, immediately scoring zero for the Punnett square. In 2024, omitting offspring phenotypes was the single most cited reason for losing the final mark in the cystic fibrosis genetics question. Using standard notation (capital for dominant, lower case for recessive) is non-negotiable.

Paper 1B 2023, Paper 1B 2024

Natural selection — using all four key terms: mutation, variation, survival, allele inheritance

Paper 2B 2023 Q01(d)(ii) and Paper 1B 2023 Q08(d)(ii) both assessed natural selection. Partial credit was common: candidates stated survival and reproduction but omitted mutation as the source of variation, or failed to state that the allele is passed to offspring. Full marks required mutation → survival advantage → increased reproduction → allele passed to next generation.

Paper 1B 2023, Paper 2B 2023

Micropropagation — small tissue size, sterile agar, and plant growth factors

Paper 2B 2023 Q06(a)(ii) showed that 'explant' alone was not credited without a reference to small size. 'Nutrients' was not credited without a named example (glucose). 'Sterile agar' and 'plant hormones/growth factors' were the key mark-earning details that weaker responses omitted. Many candidates described cuttings placed into soil instead.

Paper 2B 2023