# Explain how the structure of the rough endoplasmic reticulum (rER) is related to its function in the production and processing of proteins destined for secretion.

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

## Mark scheme (4 marks)

1. The rER is studded with ribosomes on its cytoplasmic surface, which are the sites of translation/protein synthesis.
2. Newly synthesised polypeptides are threaded into the lumen of the rER as they are made, providing a separate compartment that isolates them from the cytosol.
3. Within the lumen, proteins undergo folding and post-translational modifications such as glycosylation, which are required for their correct structure and function.
4. The extensive network of membrane-enclosed cisternae provides a large surface area and continuous transport system, so processed proteins are packaged into vesicles that bud off and are transported to the Golgi apparatus for further processing or secretion.

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-the-6b784488) · Published by Druglandscape Ltd.