Cell Fractionation

Cell Fractionation

used to isolate organelles so their structure and function can be studied individually

Why is a cold solution used in cell fractionation?

To reduce enzyme activity, preventing damage to organelles.

Why must the solution be isotonic?

To prevent osmosis; organelles don’t shrink or burst, maintaining water potential

Why is a buffered solution used?

To maintain constant pH, preventing damage to organelles.

What is homogenisation and why is it done?

Breaking open cells to release organelles; the mixture is then filtered to remove debris.

What is ultracentrifugation?

Spinning the filtered solution at different speeds to separate organelles by density.

What is differential centrifugation?

Using increasing centrifuge speeds so denser organelles form a pellet first, leaving the supernatant for the next spin.

What is removed after each centrifugation step?

The supernatant, leaving the pellet of organelles behind.

List the order in which organelles separate during cell fractionation

 Nuclei → Chloroplasts → Mitochondria → Lysosomes → Endoplasmic Reticulum → Ribosomes.

Why do organelles separate in this order?

Because of their different densities; denser organelles sediment first at lower speeds.

What is the purpose of filtering the homogenised solution?

To remove large debris and unbroken cells, leaving only organelles in solution