Yeast breaking down starch into usable energy obeys the 1ˢᵗ law of thermodynamics. Yeast converting 100 k cal of starch into 100 k cal of fat obeys the 2ⁿᵈ law of thermodynamics. Yeast destroying energy when they break down fat violates the 1ˢᵗ law of thermodynamics.
Explanation
A yeast developing on a slice of bread breaks down starch releases 100 k cal of energy. Then this energy is used to manufacture and store 100 k cal of fat. When the yeast finally breaks down the fat, that energy is consumed and lost forever.
