The sterol pathway in yeast includes several steps, in which oxygen is a cofactor. S. cerevisiae scale-down cultivation experiments indicate the impact of oscillating conditions on the metabolic activity, especially concerning the alteration within the fatty acid and sterol metabolism and changed activity of membrane-bound enzymes. They are affected by alternating oxygen availability. As revealed by flow cytometry, the respiratory activity is affected as well. The cell size distribution is concomitantly changing at oscillating glucose and oxygen availability due to the exposure to stress conditions and osmotic effects.