Random Question from SQuAD:

  What objects in organisms absorb singlet oxygen to prevent harm?

Answer:

  Carotenoids

Retrieved sentences :

1. Trioxygen (O 3) is usually known as ozone and is a very reactive allotrope of oxygen that is damaging to lung tissue.
2. Parts of the immune system of higher organisms create peroxide, superoxide, and singlet oxygen to destroy invading microbes.
3. Reactive oxygen species, such as superoxide ion (O− 2) and hydrogen peroxide (H 2O 2), are dangerous by-products of oxygen use in organisms.
4. Carotenoids in photosynthetic organisms (and possibly also in animals) play a major role in absorbing energy from singlet oxygen and converting it to the unexcited ground state before it can cause harm to tissues.
5. Oxygen is toxic to obligately anaerobic organisms, which were the dominant form of early life on Earth until O 2 began to accumulate in the atmosphere about 2.5 billion years ago during the Great Oxygenation Event, about a billion years after the first appearance of these organisms.
6. Photosynthesis releases oxygen into the atmosphere, while respiration and decay remove it from the atmosphere.
7. Lower levels of reactive oxygen species initiate systemic acquired resistance, triggering defense-molecule production in the rest of the plant.
8. Oxygen gas is poisonous to the anaerobic bacteria that cause gas gangrene, so increasing its partial pressure helps kill them.
9. Oxygen gas (O 2) can be toxic at elevated partial pressures, leading to convulsions and other health problems.
10. Only a few common complex biomolecules, such as squalene and the carotenes, contain no oxygen.
11. Another form (allotrope) of oxygen, ozone (O 3), strongly absorbs UVB radiation and consequently the high-altitude ozone layer helps protect the biosphere from ultraviolet radiation, but is a pollutant near the surface where it is a by-product of smog.
12. Highly concentrated sources of oxygen promote rapid combustion.
13. Bundle sheath chloroplasts do not carry out the light reactions, preventing oxygen from building up in them and disrupting rubisco activity.
14. Chloroplasts stimulate both responses by purposely damaging their photosynthetic system, producing reactive oxygen species.
15. Carbon monoxide poisoning, gas gangrene, and decompression sickness (the 'bends') are sometimes treated using these devices.
16. Reactive oxygen species also play an important role in the hypersensitive response of plants against pathogen attack.
17. All fats, fatty acids, amino acids, and proteins contain oxygen (due to the presence of carbonyl groups in these acids and their ester residues).
18. Oxygen toxicity to the lungs and central nervous system can also occur in deep scuba diving and surface supplied diving.
19. Oxygen, as a supposed mild euphoric, has a history of recreational use in oxygen bars and in sports.
20. Most of the mass of living organisms is oxygen as it is a part of water, the major constituent of lifeforms.
21. Free oxygen also occurs in solution in the world's water bodies.
22. It is also produced in the troposphere by the photolysis of ozone by light of short wavelength, and by the immune system as a source of active oxygen.
23. The O 2 surrounding these other planets is produced solely by ultraviolet radiation impacting oxygen-containing molecules such as carbon dioxide.
24. High levels of reactive oxygen species will cause the hypersensitive response.
25. Acute oxygen toxicity (causing seizures, its most feared effect for divers) can occur by breathing an air mixture with 21% O 2 at 66 m or more of depth; the same thing can occur by breathing 100% O 2 at only 6 m.