# "Explain" questions — OCR A-Level Biology A (H420)

> 136 questions · biology

## How to answer

WHAT + WHY. Every point paired with a because. Structure: X happens because Y. This causes Z because … Assessment Objective: AO2. Every "explain" answer on this spec is marked against exactly this pattern.

## Sample questions

1. [Explain how the structure of a sieve tube element is adapted to allow the mass flow of assimilates through the phloem.](https://www.gradenine.co.uk/q/explain-how-the-structure-of-a-00bc134c)
2. [A research team used CRISPR-Cas9 to introduce a loss-of-function mutation into a gene encoding a transcription factor in…](https://www.gradenine.co.uk/q/a-research-team-used-crispr-cas9-to-0402dfed)
3. [Explain why the tertiary structure of an enzyme is essential for its function, referring to the role of bonds that maint…](https://www.gradenine.co.uk/q/explain-why-the-tertiary-structure-of-05e21554)
4. [Explain how the structure of a sieve tube element is adapted for the mass flow of assimilates through the phloem.](https://www.gradenine.co.uk/q/explain-how-the-structure-of-a-063380d8)
5. [Explain how the structure of a sieve tube element is adapted for its function in the phloem.](https://www.gradenine.co.uk/q/explain-how-the-structure-of-a-09733a59)
6. [Explain why totipotency in plant cells makes it possible to produce large numbers of genetically identical plants from a…](https://www.gradenine.co.uk/q/explain-why-totipotency-in-plant-cells-09b2d263)
7. [Explain why a restriction endonuclease and DNA ligase are both required when inserting a human gene into a bacterial pla…](https://www.gradenine.co.uk/q/explain-why-a-restriction-endonuclease-and-09f9aea4)
8. [Explain why a habitat with a high species richness does not necessarily have a high biodiversity index.](https://www.gradenine.co.uk/q/explain-why-a-habitat-with-a-0aa08bca)

## Related

- [OCR A-Level Biology A (H420) revision notes](https://www.gradenine.co.uk/learn/ocr-a-level-biology-a-h420)
- [OCR A-Level Biology A (H420) past papers](https://www.gradenine.co.uk/past-papers/ocr-a-level-biology-a-h420)
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