The growth of yeast in liquid medium, as the growth of many single celled organisms, is characterized by distinctable phases. At first, when cells are placed into a new medium, lag phase occurs, marked by slight or no change in cell density, while cells alter gene expression in order to adapt to their new environment and begin collecting (and/or synthesizing) important compounds. Among these are minerals, such as zinc or phosphorous, vitamins, carbon sources (energy), such as glucose, glycerol or lactate, and nitrogen sources, such as ammonia or amino acids. Altered gene expression especially involves nutrient dependent enzyme production. After this delay, which lasts between 3 to 15 hours, Log phase begins, where cells begin growing. Cell cycle is initiated and cells start to divide, cell density rises exponentially. When nutrients start to become limited, growth rates are slowed down and cells prepare for starvation. Storage carbohydrates, like trehalose, are synthesized. When starvation finally occurs, cells enter stationary (or post-log) phase, characterized by significant shutdown of all metabolic functions. Cell cycle arrests in G0.
- -> pyruvate
Organic acid cycle
- aerob vs anaerob metabolism?
- favored metabolism?
- when is which pathway switched on/off?