Runs

Definition

Runs are the straight-line movements exhibited by motile prokaryotic cells, typically in response to environmental stimuli. These are part of the chemotaxis process, where cells move toward or away from chemical signals.

5 Must Know Facts For Your Next Test

1. Runs are usually interspersed with tumbles, where the cell changes direction.
2. During a run, flagella rotate counterclockwise to propel the cell forward.
3. Runs increase in duration when a cell moves toward an attractant or away from a repellent.
4. Chemoreceptors on the cell surface detect environmental stimuli that influence runs.
5. Energy for runs is derived from proton motive force across the cell membrane.

Review Questions

• What role do flagella play in the 'runs' of prokaryotic cells?
• How do chemoreceptors affect the duration and direction of a run?
• What is the energy source that powers runs in prokaryotic cells?

Related terms

Tumbles: Random changes in direction occurring between runs.

Chemotaxis:

Movement of an organism in response to a chemical stimulus.

Flagella:

Long, whip-like structures used for movement by certain prokaryotic cells.