Cells growing in culture need to have the growth media replaced at regular intervals, approximately every 3 to 4 days. We need to do this because healthy rapidly growing cells deplete the nutrients in the media over that time period and without those nutrients, they would die off. The task is fairly simple, requiring you to remove the old media using a pipette or vacuum aspirator and replacing the media with a suitable volume of fresh growth media.

A vacuum aspirator is simply a side neck Erlenmeyer flask with a stopper and some tubing. The tubing from the side neck is attached to the vacuum source inside the hood and Pasteur pipettes are used to remove the old media.

The materials you will need to bring into the hood for this task are a pipette controller, a vacuum flask, a box of Pasteur pipettes, several 10-milliliter pipettes, and your growing cells.

### Learning Objectives:

- 1.3 - Feed cells to maintain life.