catabolism of proteins and fats
2006-07-26 17:02:48 · 3 answers · asked by kristi 2 in Education & Reference ➔ Higher Education (University +)
Because it is the only method by which they can produce any ATP without oxygen.
It was first to evolve, and now cells have evolved better methods but which to attain energy, explicitly speaking, aerobic respiration.
2006-07-26 17:07:01 · answer #1 · answered by Stephanie S 6 · 0⤊ 0⤋
If there is no oxygen around the cell has little option but to use fermentation.
This is because although the cell is producing ATP (glucose to pyruvate produces ATP) this requires NAD+ which in aerobic conditions is produced by the TCA cycle. Conversion of pyruvate to lactate or ethanol produced NAD+ from NADH allowing the cell to continue its metabolism.
Some yeast have be known to produce ethanol even when oxygen is readily available, it is thought that this kills other microbes in the area due to the toxic effects of ethanol.
2006-07-27 00:07:12 · answer #2 · answered by dunnerzplant 2 · 0⤊ 0⤋
I think it's because the process to make ATP is an aerobic process, so it requires oxygen. When oxygen is not present it has to switch over to an anerobic process for energy which could be fermentation.
2006-07-27 00:08:03 · answer #3 · answered by tooqerq 6 · 0⤊ 0⤋