Yeast is not an enzyme but a eukaryotic organism classified under fungi. It serves as a rising agent in bread-making and is also utilized as a model organism in biological research. While yeast contains enzymes, such as alcohol dehydrogenase, it is important to note that not all yeasts grow like traditional fungi. Some, like baker's yeast, reproduce by budding, while others, such as Candida, exhibit dimorphic growth, forming filaments. Eduard Buchner's research in the late 19th century established that alcoholic fermentation is driven by yeast enzymes rather than the yeast cells themselves, leading to his Nobel Prize in Chemistry in 1907. Despite variations in growth forms, all yeasts are categorized as fungi.