Question

The bread or idlin dough rises because of

Answer 1

The bread or idli dough rises because of production of carbon dioxide. Glycolysis is the metabolic pathway which results in the formation of carbon dioxide.

Answer 2

It rises because of accumulation of CO2 inside which make holes and causes to rise in size.

More:

Yeast respiration is the main reason here.

While it respires,

$Glucose \longrightarrow {}_{(In \ cytoplasm)} Pyruvate \longrightarrow {}_{(absence \ of \ O_2)} Ethanol + CO_2 + ATP$.

Since it is an anaerobic process, less molecules of ATP is formed here.