What's the simile and what two things are being compared in. the letters stirred together like a thick, messy mush

A simile is a figure of speech that directly compares two things through the use of words such as "like" and "as." In this case, the simile being employed is "like a thick, messy mush," and the two things being compared are the letters, and the thick, messy mush. The author wants to convey the idea of the letters being illegible, or confusing.

the krebs cycle and electron transport occur in the mitochondria, though other than that i would need to know more information.