Yeast are unicellular fungi, characteristics of fungi complex cells with internal organelles, similar to plants butnon-photosynthetic. cannot utilise sun as source of energy so rely on chemicals for growth and energy. Two types indistinguishable by eye, domesticated by man and not found in wild, ale yeasts – Saccharomyces cerevisiae, lager strains saccharomyces pastorianus (previously S. carlsbergensis). Sugars (including glucose, maltose and sucrose)
block receptor sites and cause yeast cells to deflocculate.