Yeasts are heterotrophic. They require a reduced carbon source such as acetate and a nitrogen source such as ammonium sulfate. Yeasts can use a variety of organic nitrogen compounds, including urea and various amino acids. They also require the vitamin biotin, a variety of salts and trace elements. Knowledge check: What do aerobic and anaerobic mean? [answer]  Normal yeast can grow either aerobically or anaerobically. Yeast, under aerobic conditions completely oxidize sugars to carbon dioxide and water. However, under anaerobic conditions, yeast can convert sugars only to carbon dioxide and ethanol, recovering less of the energy.