Yeast is a microscopic unicellular, uni nucleate fungus varying from 2-25 micron in length and 1-5 micron in width.
Each cell is rounding, oval or elliptical in shape enveloped by a cell wall. The cell wall is mainly composed of two polysaccharides, glucan and mannan, proteins, lipids and chitin. Inner to the cell wall, there occurs lipoproteinaceous cell membrane, which surrounds the protoplasm, mitochondria, golgi apparatus.
The reserve food is found in the form of glycogen, oil globules and volution granules. A large vacuole containing hydrolytic enzymes surrounded by a single unit membrane occurs at the centre of the cell. The nucleus is distinct being enveloped by two unit membranes and perforated by pores.
Growth
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Growth of yeast takes place by all over all increase in cell size.
Nutrition
Nutrition is saprophytic. It utilizes sugar containing nutrients from its habitat.
Reproduction
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Yeast reproduces by Vegetative and sexual methods.