# Explain how the structure of the smooth endoplasmic reticulum (sER) is related to its functions in eukaryotic cells.

> IB DP Biology Standard Level (2023 syllabus) — B2.2 Organelles and compartmentalisation · Explain · 4 marks

## Mark scheme (4 marks)

1. The sER is an interconnected network of membrane-bound tubules/cisternae, providing a large surface area for enzyme attachment and metabolic reactions.
2. The sER lacks ribosomes on its membrane, distinguishing it structurally from the rER and allowing it to specialise in lipid/phospholipid synthesis rather than protein production.
3. The sER is continuous with the nuclear envelope and rER, forming a connected membrane system that allows transport of lipids and other molecules through the cell.
4. In liver/muscle cells, the sER contains transmembrane proteins (e.g. glucose-6-phosphatase / calcium pumps) embedded in its membrane, enabling specific functions such as detoxification of drugs/toxins or calcium ion storage and release for muscle contraction.

## Key terms

- [smooth endoplasmic reticulum](https://www.gradenine.co.uk/glossary/smooth-endoplasmic-reticulum)

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-the-94fa8fb3) · Published by Druglandscape Ltd.