Yeast are classified in Domain Eukarya and Kingdom Fungi. These are heterotrophs which means they must obtain food from pre-formed organic compounds. Yeast are single-- celled (unicellular) fungi.
Yeasts are placed in the group ascomycetes or sac fungi because of their method of reproduction. Yeasts are unicellular and reproduce asexually by a process called budding. The DNA within its nucleus is replicated and the cell's cytoplasm is divided unequally into a parent and a daughter cell- a smaller bud. However, each has an identical set of genes. The bud may eventually break off from the parent cell, or remained attached until it also forms a bud.
Yeast can also reproduce sexually-two haploid nuclei fuse to form a diploid zygote.
Some yeasts are the cause of a fungal disease in the vaginal tract known as a yeast infection. Yeasts carry out fermentation which is a process by which they obtain a small amount of ATP from an energy source like glucose. Wine is formed as yeast cells ferment the sugar in grapes producing alcohol and carbon dioxide as the waste products of this reaction. Bread dough rises when yeast cells are added due to the carbon dioxide released from fermentation.
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