yeast growth

LAG PHASE
changes in pressure, temperature and nutrients
biosynthesis of enzymes needed for metabolism
oxygen rapidly removed from wort for sterol and fatty acid synthesis

LOGRITHMIC PHASE
fast yeast reproduction
uptake of nutrients and sugars
heat is generated
volatiles are driven off

DECLINING PHASE
increase in acidity, alcohol and carbon dioxide
utilization of glycogen and sterol reserves
reproduction ceases
flocculation