16

Short answer This is a difficult question to answer. As far as I am aware, asphyxiation results in excitotoxicity, which causes unconsciousness, brain damage and eventually, death. Background Asphyxia is a condition of the body that occurs from severely inadequate oxygen supply, or because of excessive carbon dioxide in the body (First Aid and CPR courses)...


14

Humans have no anaerobic respiration, if we define this as oxidation of a substrate with an external electron acceptor other than oxygen. In humans, the terminal electron acceptor in respiration is always oxygen, which is reduced at complex IV in the respiratory chain. Alternative electron acceptors are mostly found in bacteria and archaea. I would call the ...


11

The background to phosphine production on Earth can be found in a review entitled “Natural Products Containing ‘Rare’ Organophosphorus Functional Groups” by Petkowski et al. in Molecules 24, 866 (2019). The four authors are also co-authors of the Nature Astronomy paper. They state (my emphasis): The detailed biosynthetic pathway for microbial phosphine ...


7

Detection and role of phoshine in phosphorus cycle was first discussed in 19881. They examined phosphorus cycle in open-air sewage treatment plants where they discovered a gas releasing from sediments of 1-2 meter deep water which was found to be phosphine. They calculated that 5 g of phosphine was released from 2000 m3 of sewage. They also further proposed ...


7

Consider this from the point of view of integrating whole body metabolism. The body operates on a fuel economy built around glucose. Active muscle produces lactate (C3) which is exported to the liver through the bloodstream. Liver converts lactate to glucose (C6) which is then exported to the tissues. What if muscle produced ethanol (C2)? Liver ...


6

There are organisms with anaerobic metabolism that tolerate oxygen: aerotolerant anaerobes. "Anaerobic" refers to the metabolic system. You cannot be sure of oxygen tolerance based solely on metabolic system. Factors influencing the tolerance of anaerobic bacteria to oxygen Here is why this is a facultative anaerobe. This organism does not gain weight ...


6

The problem lies in soil bacteria. There has been a project on a larger scale: Biosphere 2. After their initial trial they realised $O_2$ levels are getting much lower from what was predicted. The scientists team investigated the problem deeper and came to the conclusion that there was a lot of dead organic matter in the soil, which got consumed by aerobic ...


5

There are three worms which have been found in the sediment of the mediterranean seafloor, which not only live without oxygen but also do not tolerate the exposure to oxygen. They belong to the metazoans, for more details see either the report (reference 1) or the original article (reference 2). They reach a size og about 1mm. References: Scientists ...


5

The enzyme catalysing this reaction in mammals is lactate dehydrogenase of which there are two major isoforms: LDHA and LDHB. The general reaction scheme can be shown as: In muscles LDHA reduces pyruvate to lactate consuming one NADH. This gets rid of the electrons which would normally go through the respiratory chain. The lactic acid is then transported to ...


5

Sulfates in water would not be liquid. Their melting points are far to high. When a sulfate dissolves into sulfate ions and some cation such as potassium, we say it is solvated, not liquid. Sulfates would also not be present as gasses due to their ionic nature as well as high molecular weights. So that leaves solvated sulfate ions and solid sulfates that ...


4

Muscle tissue is a good example of anaerobic fermentation. Lactic Acid is fermented and builds up in this tissue when we do large amounts of exercise. We use the Pyruvate molecule and LDH to produce Lactate when required but it is only for short bursts of energy in specific tissues. Try a google image search for the glycolytic pathway. Usually Aerobic and ...


4

You may need to clarify your question: As written, this would be the biological equivalent of a perpetual motion machine. No such organism could reproduce without either violating the first and second laws of thermodynamics, or ultimately evaporating into nothingness as it divides.


3

I did a bit of reading myself, and it seems as if Loricifera are the only multicellular obligate anaerobes. I see your point with niches for anaerobic organisms in deep water. Many organisms near the hydro-thermal vents use anaerobic cellular respiration. From my understanding of Loricifera, it seems as if they would utilize chemosynthesis as their method ...


3

Someone else may come along later with a definitive answer but I found this question intriguing so here are my thoughts: The standard redox potentials of the mitochondrial ETC carriers are: NAD⁺/NADH -0.32 V complex I (Fe-S) -0.27 V complex II (cyt b₅₆₀) -0.08 V complex III ((cyt c₁) +0.23 V complex IV (cyt a₃) +0.38 V O₂/H₂O ...


3

It is not uncommon for cells to have parallel pathways for same outcome. This ensures foolproof response and makes the system robust. E.coli also has another sensor for aerotaxis (Aer and Tsr proteins). See my answer on your previous post and the linked paper. Also look for coherent feed forward network motifs.


3

For glycolysis this is really not so much of an issue, because the ATP yield is fixed by stoichiometry. The early biochemistry work by Embden, Meyerhof, Parnas and other that mapped out the reaction mechanisms of the glycolytic pathway shows that you always obtain exactly 2 ATP per glucose; this is simply the stoichiometry of those reactions. There are a ...


2

I think only b.) is true. a. I cannot find evidence that maltose is toxic to yeasts (and I would hardly believe it, because it is a glucose dimer), however I found evidence, that yeasts might need the presence of oxygen to process maltose. 1977 - The Requirement of Oxygen for the Utilization of Maltose, Cellobiose and D-Galactose by Certain Anaerobically ...


2

I mentioned in comment quite early "apparently humans don't do anaerobic respiration at all. They only do a)aerobic respiration and b)fermentation. Humans can't use nitrate or sulfite as acceptors in the electron transport chain" I'll expand on that a bit.. https://www.khanacademy.org/science/biology/cellular-respiration-and-fermentation/variations-on-...


2

This is really interesting because the answer largely depends on the severity of the damage, the length of the damaging condition, the type of damage incurred, and the type of cell incurring the damage. For a real life example, irreparable DNA damage as by irradiation or drugs tends to be lethal to a cell. The severity of the damage may affect how long a ...


2

No, I think this fails even on simply definitional terms. That is, Life is (sometimes) defined as meeting certain criteria, such exhibiting growth, metabolism, and response to stimuli. Those will all require intake of some external substance at some point. To get even more pedantic, all cells have a cell membrane, which is selectively permeable to certain ...


1

Any sealed container can become anaerobic relatively quickly if there are oxygen consuming organisms inside (which there probably are if it's not sterilized). So, growth of anaerobes should always be a concern when using a sealed container for food storage, and proper temperatures for such storage should be considered. A container like the one you describe ...


1

I notice that you don't specify pH, which might be important. I don't know if you can put in too much reducing agent (I suspect not), but a large excess is often required as the equilibrium constants for disulfide exchange reactions are typically close to unity (see Cleland, 1963). I also don't know if any of following has any relevant to your problem (...


1

Yes, many microbes can use electron acceptors other than oxygen. https://en.wikipedia.org/wiki/Anaerobic_respiration https://www.sciencedirect.com/science/article/pii/S0168165611000289


1

Yes, (obligate) anaerobes die in the presence of oxygen (at atmospheric levels). They do not have the detoxifying enzymes that convert toxic metabolic products such as hydroxyl racials or superoxide anions into nontoxic H2O or O2. These enzymes present in aerobic and faculative anaerobic organisms are superoxide dismutase, peroxidase, among others. ...


1

1) Yes, most cells in the body derive energy from oxidative metabolism, unless oxygen is not available for some reason. There are some exceptions, for example red blood cells lack mitochondria and so have no respiration, and various types of rapidly proliferating cells such as activated immune cells have high glycolysis and lactate production (for reasons ...


1

IMO, the answer to this one is (b). The reason is the (often overlooked) Pasteur effect: oxygen inhibits fermentation. The Pasteur effect occurs in many cell types, including skeletal muscle, brain, heart, liver, bacteria and yeast (Tejwani,1978) . The mechanism of the Pasteur Effect has been much studied and debated and it it probably true to say that it ...


1

You're right, the answer is b since the presence of oxygen would lead to aerobic respiration and not fermentation. If maltose was toxic, the yeast wouldn't grow. Proteins are required for growth, but the yeast is growing. Any temperature that is extreme enough to prevent fermentation would also prevent other cellular processes and the yeast wouldn't ...


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