People are warm-blooded animals, and most of their energy is used to maintain their body temperature in winter, and very little in summer, so they are full of energy in winter. People and animals can't do photosynthesis like green plants, nor can they do chemical synthesis like nitrifying bacteria. They can only rely on the ready-made organic matter in the external environment to maintain their own life activities. This metabolic type belongs to heterotrophic type.

In addition, the metabolic types of fungi and most saprophytic or parasitic bacteria are also heterotrophic. In a word, in the process of assimilation, organisms convert ready-made organic matter absorbed from the external environment into their own components and store energy. This metabolic type is called heterotrophy.

Extended data are usually distributed in high sugar content and acidic environment, such as the surface of vegetables and fruits and the soil of vegetable gardens and orchards. Yeast is a facultative anaerobic microorganism, which decomposes carbohydrates into carbon dioxide and water under aerobic conditions.

In the absence of oxygen, sugar will be decomposed into carbon dioxide and alcohol. Yeast is widely used in production. Besides well-known brewing and fermentation, it can also be used to produce organic acids and extract various enzymes.

Baidu encyclopedia-metabolism