# Explain how the process of endocytosis allows a cell to take up large molecules that cannot cross the plasma membrane by diffusion or transport proteins.

> IB DP Biology Higher Level (2023 syllabus) — B2.1 Membranes and membrane transport · Explain · 4 marks

## Mark scheme (4 marks)

1. The plasma membrane forms an indentation / invaginates around the large molecule or particle
2. The membrane pinches off to form a vesicle inside the cell, enclosing the molecule
3. The process requires energy (ATP) / is an active process
4. The molecule is therefore transported into the cell without ever crossing the phospholipid bilayer / the bilayer remains intact

## Key terms

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

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-process-of-endocytosis-7545415c) · Published by Druglandscape Ltd.