Explain the ways in which glucose is broken down in absence or shortage of oxygen.

Explanation

The first step in the breakdown of glucose. Glucose is converted to pyruvate.
Pyruvate in the absence of `O_(2)` may be converted to ethanol, `CO_(2)` and energy (in yeast).
Pyruvate in the shortage of `O_(2)` may be converted to lactic acid and energy.(in human body).