Your first answer is talking about brewing - and the preperation of foods - alcohol. This answer talks about respiration in organisms.
Before we begin
An atom is the smallest amount of any chemical possible and not seen by the human eye.
A molecule is a collection of atoms bonded together either of the same chemical or of another attracted chemical. Molecules are still too small to be seen by the human eye.
Note not all chemicals want to bond with all other chemicals. Acids don't bond with Acids and Alkalines do not bod with Alkalines.
Some chemicals need to bond with attracted chemicals. Acids with Alkalines. Chemicals find it easier to bond with certain other Chemicals than others.
A. breathing without oxygene.
B. breathing with oxygene.
A) In the day with the use of day light plants do not breathe in oxygene O2 (lots of molecules made up of 2 oxygene atoms) but breathe it out as a waste product. Plants breathe in CO2 (carbon di oxide = lots of molecules of 1 carbon atom and 2 oxygene atoms) and with the energy from the sun light they form carbohydrates with the water H2O (lots of molecules of 2 hydrogen atoms and 1 oxygene atom) they absorb from their roots. CO2 + H2O = carbohydrate and O2
B) Oxygene is used to burn food and produce energy in animals. Chemically complex molecules of food are eaten and broken up first by digestive enzymes and then the constituent chemicals in the food eaten form simpler molecules with the oxygene breathed in from the air. Nearly all non toxic molecules prefer to bond with oxygene than any other molecule. Of course some chemicals like iron are absorbed into the blood stream and feed the animal. Carbon is a waste product and ultimately bonds with the oxygene to form CO2 and is breathed out by the animal. Urea (ammonia) and solid waste are excreted by the animal but that is digestion and not entered into in the aerobic respiration calculation. O2 + food = all our nutrients and CO2.
Plants do breathe oxygene at night in the dark.
Anaerobic respiration is certainly simpler and I would guess more efficient, because there is not ammonia or solid waste that needs to be got rid of. Animals need to hunt or search for food. Plants just need to be watered. They do not even need animals to breathe out CO2, because they do that at night. As people have calculated without plants animals have no O2 to breathe.
The same happens but in a different way with plants under water. Advanced animals under water like Whales, Dolphins and Seals need to surface in order to breathe air regularly.
There are plants deep in the ocean near volcanic emissions of sulphur that breathe neither O2 or CO2, there may even be animals. Sulphur kills both plants and animals above water.
I hope that this is good enough. Good luck.
