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H1 Biology 8876 · Nov 2023BiologyPaper 1Most challenging

Paper 1 Q8 — Parts of a phospholipid

Membranes — the phosphate–glycerol head vs the fatty acid tails

What the examiners said

“A large proportion of candidates… did not realise that the structure labelled 2 is the head of a phospholipid molecule and includes the part to which the fatty acid tails are attached. It must therefore include phosphate and glycerol.”

Try the question

In a phospholipid, which components make up the hydrophilic ‘head’ region to which the fatty acid tails attach?
Examiner report: “Candidates did not realise the labelled head must include phosphate AND glycerol.”

Explore — label the phospholipid

Click through the regions of a phospholipid. See how glycerol links the phosphate head to the two fatty acid tails, and why the head is hydrophilic.

The head (region ‘2’ in the exam) is phosphate + glycerol together. The tails are the two fatty acids esterified to the glycerol.

Original reconstruction inspired by the misconceptions described in the Singapore-Cambridge GCE A-Level H1 Biology 8876 November 2023 Examiner Report. Not the actual examination question. For classroom exploration.

Made by lookang, using Claude Fable 5. More resources: iwant2study.org