# Explain how the ultrastructure of a goblet cell in the intestinal epithelium is adapted for the secretion of mucus.

> IB DP Biology Higher Level (2023 syllabus) — B2.3 Cell specialisation · Explain · 4 marks

> Goblet cells are unicellular glands interspersed among the columnar epithelial cells lining the small intestine. They continuously synthesise and secrete mucus glycoproteins (mucins) onto the epithelial surface.

## Mark scheme (4 marks)

1. Abundant rough endoplasmic reticulum (rER) provides an extensive membrane system for the synthesis of mucin glycoproteins by membrane-bound ribosomes.
2. A large, well-developed Golgi apparatus processes and glycosylates the mucin proteins, packaging them into secretory vesicles for export.
3. Numerous large mucus (secretory) granules / vesicles in the apical cytoplasm store mucin ready for rapid exocytosis onto the epithelial surface.
4. Many mitochondria supply the ATP needed to drive active synthesis, protein modification, and the exocytotic secretion of mucus.

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-ultrastructure-of-a-98036d73) · Published by Druglandscape Ltd.