Aerobic respiration needs oxygen. One molecule of glucose is broken down to create 34 to 36 molecules of ATP, the cell's energy currency, during aerobic respiration. Aerobic respiration would cease if there was no oxygen available, and organs that rely on aerobic respiration would perish. All living things are aerobes; that is, they require oxygen for their survival.
An anaerobe is a microbe that cannot survive in air. Most bacteria are anaerobic, as are most other organisms that do not use oxygen for cellular respiration. The term "anaerobic" means "without oxygen." Anaerobic microbes can still grow and divide, but they do not use oxygen as a terminal electron acceptor (the thing that gets electrons from cells' metabolism and uses them to build themselves or other substances). So an anaerobic environment does not prevent these microbes from proliferating. In fact, under certain conditions, anaerobic microbes can grow faster than those that can use oxygen.
Some archaea are also anaerobic. They lack the ability to produce their own energy through photosynthesis or any other process and thus must obtain their energy from other sources. Some archaea can switch between using oxygen as their primary energy source and hydrogen as their primary energy source when given the opportunity. Others are strictly anaerobic.
Eukaryotes are organisms that have evolved beyond the single-celled stage.
Organisms can only break down 6-carbon glucose into two 3-carbon molecules in the absence of oxygen. As previously stated, glycolysis only produces enough energy to make two (net) ATP per molecule of glucose. Aerobic respiration, on the other hand, breaks glucose all the way down to CO2, creating up to 38 ATP. An anaerobic organism cannot use oxygen as a terminal electron acceptor because it lacks the enzymes necessary for this process.
Glycolysis is used by most organisms as a source of energy during times of rapid cell division or under conditions of oxygen deprivation. It can also be used as a mechanism for generating toxic compounds under anoxic conditions. For example, when oxygen levels are low, some bacteria will switch to using glycolysis instead of oxidative phosphorylation to generate energy and continue growing.
In conclusion, glycolysis cannot produce sufficient energy under normal conditions to support life. However many anaerobic organisms have evolved mechanisms to extract energy from glycolysis under these circumstances.
Without oxygen, organisms must make ATP by anaerobic respiration, which yields just two molecules of ATP per molecule of glucose. Although anaerobic respiration creates less ATP, it does do much more quickly. Aerobic cellular respiration, on the other hand, creates ATP at a slower rate. But it can be done with oxygen present.
In fact, many bacteria live in this "aerobic" state all the time, using oxygen as their respiratory system. They produce energy anaerobically and use it for growth and reproduction.
Eukaryotic cells such as those found in animals, plants, and some unicellular eukaryotes (such as amoebas) have more complex structures and perform more specialized functions. They cannot survive without oxygen (unless they are protected inside a vacuum-packed fish or meat product). However, even though they cannot survive without oxygen, these cells can still make some small amounts of ATP anaerobically through special enzymes called oxydases.
The mitochondria of eukaryotic cells also contain their own DNA, but it is not identical to the DNA contained within the nucleus of the cell. Instead, it is its own separate genome, which was probably inherited from the original bacterium that engulfed another organism. This means that both bacteria and humans have their own unique genetic material - but only humans have nuclear material inside of their cells while bacteria have no need for this part of the genome.