The yeast comes alive and starts eating the sugars, creating carbon dioxide and alcohol -- essentially it's burping and sweating, which is what bread is.
酵母们被唤醒，开始吞食糖原， 释放二氧化碳和酒精， 就像是吃饭吃得满头大汗，到头来再打个饱嗝，就得到了面包。