Pearson Edexcel International GCSE Biology · specification 4BI1 · Paper 2 | Whole paper: All content including bold B statements · Free · no account needed
2(c) Biological molecules (4BI1 specification)
The main food groups, their elements, their building blocks, the tests that identify them, and how enzymes act on them.
Learn it on Incandio
The 3 Incandio pages that teach this — each explained in full, then proved in marked questions, taught back to an AI pupil and defended in a debate. Completely free.
- Comparing Cells, and Stem Cells — What plant and animal cells share and where they differ — then why a cell specialising is one of the most powerful ideas in biology.
- Carbohydrates, Proteins and Lipids — The three big food molecules — what they are made of, what they are built from, and how to test for them.
- Enzymes: Catalysts With a Shape — Why a protein with a hole in it speeds up a reaction, and why heat destroys that ability permanently.
The teaching route this belongs to: Topic 2 · Structures and functions in living organisms (Biology) — the lessons in order, with every gate.
Specification coverage
Topic 2 Structures and functions in living organisms (c) Biological molecules — statements 2.4–2.12B (includes bold B statements assessed on Paper 2 only)
Assessment objectives: AO1, AO2, AO3. Suggested learning time: 90 minutes.
Required knowledge
- The chemical elements present in carbohydrates, proteins and lipids
- The basic units: simple sugars for carbohydrates, amino acids for proteins, fatty acids and glycerol for lipids
- Food tests: Benedict's for reducing sugars, iodine for starch, Biuret for protein, ethanol emulsion for lipids
- Enzymes as biological catalysts and proteins that function in the synthesis and breakdown of molecules
- The effect of temperature and pH on enzyme activity, and the meaning of denaturation
- Bold B statements: the mechanism of enzyme action in more depth, including active site and substrate specificity
Required skills
- Carry out and interpret each food test, including the colour change in both directions
- Explain enzyme behaviour in terms of shape rather than 'the enzyme dies'
- Plot and interpret rate-of-reaction data against temperature or pH
- Describe and evaluate the required practical: Investigate how enzyme activity is affected by changes in temperature, and use qualitative food tests to identify starch, reducing sugars, protein and fat.
How it is examined
- Multiple-choice and short-answer recall
- Application of the content to an unfamiliar context
- Extended open-response, marked on the quality of a connected explanation
- Practical questions on method, variables, data and sources of error
Common mistakes
- Saying enzymes are 'killed' by heat. They are denatured — the active site changes shape, so the substrate no longer fits.
- Giving the Benedict's positive result as 'orange' only. The colour depends on concentration and the full sequence is examinable.
- Claiming that raising temperature always raises the rate. It does until the optimum, then activity falls sharply.
This page maps the specification. The pages above teach it, and the Biology lessons hold the whole course — completely free.