# Explain how the polarity of water molecules arises from their structure and outline one consequence of this polarity for living organisms.

> IB DP Biology Standard Level (2023 syllabus) — A1.1 Water · Explain · 4 marks

## Mark scheme (4 marks)

1. Oxygen is more electronegative than hydrogen, so the shared electrons in each O–H bond are pulled towards the oxygen atom.
2. This creates partial negative charge (δ−) on oxygen and partial positive charges (δ+) on the hydrogen atoms, giving the molecule a permanent dipole.
3. The bent / V-shaped geometry of the water molecule means the dipoles do not cancel, so the molecule is polar overall.
4. One consequence for living organisms: polarity allows water to act as a solvent for polar/ionic substances (e.g. glucose, ions, amino acids), enabling transport of nutrients, waste products, or metabolites in biological fluids / facilitating metabolic reactions in aqueous solution.

## Key terms

- [polarity](https://www.gradenine.co.uk/glossary/polarity)

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-polarity-of-water-1037e7c4) · Published by Druglandscape Ltd.