2.10 Cell Compartmentalization

Membranes create compartments

Internal membranes divide a eukaryotic cell into compartments — the membrane-bound organelles. This compartmentalization lets the cell run many different, even incompatible, reactions at the same time in separate spaces.

Why compartments help

Compartments create localized conditions (like the acidic interior of a lysosome) and keep reactants concentrated together, increasing efficiency. The nucleus separates transcription from translation, giving eukaryotes extra control over gene expression.

Key terms

Compartmentalization

Using internal membranes to divide the cell so many reactions can run at once.

Membrane-bound organelle

A compartment enclosed by membrane with its own specialized conditions.

Localized conditions

Unique internal environments (like a lysosome's acidity) that suit specific reactions.

Nucleus separation

Keeps transcription (inside) apart from translation (outside), adding regulation.

Efficiency benefit

Concentrating reactants in one compartment speeds up reactions.

Try an AP-style question

Lysosomal enzymes work best at pH ~5, while the cytosol is about pH 7.2. What is a benefit of this arrangement?

1. If a lysosome leaks, its enzymes are much less active in the cytosol
2. The enzymes can digest the lysosome's own membrane safely
3. The cytosol's pH activates the lysosome's membrane
4. The enzymes are most active if they leak into the cytosol