17 votes
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Why do you die if you cannot breathe?

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 ...
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14 votes
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Are humans capable of both anaerobic respiration, and lactic acid fermentation?

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 ...
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12 votes
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Which anaerobic environments would exist without aerobic life?

In the question body it says: After the great oxygenation event, there was oxygen in the atmosphere but no layers of aerobic life to stop it from diffusing to the bottom of the ocean or deep ...
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11 votes
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How is it thought that phosphine is synthesized by living organisms on Earth?

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 (...
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7 votes

How is it thought that phosphine is synthesized by living organisms on Earth?

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 ...
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7 votes
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Why don't animals produce alcohol

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 ...
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6 votes
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Facultative anaerobic organism

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 ...
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6 votes
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What are the requirements for a stable carbon cycle in sealed "bottle gardens"`?

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 ...
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  • 336
6 votes

Which anaerobic environments would exist without aerobic life?

Deep sea hydrothermal vents release reducing chemicals like sulfide ($S_2^-$) and ferrous iron ($Fe^{2+}$). These chemicals establish anaerobic conditions abiotically[1]. [1] "M. jannaschii uses ...
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5 votes

Is there any organism that is born with all the nutrients and resources needed for their entire lifetime?

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 ...
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5 votes
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What's the biggest obligate anaerobic organism discovered till now?

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 ...
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5 votes
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How does reversibility of lactic acid fermentation work?

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 ...
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5 votes
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Do sulfate reducing bacteria ingest their sulfate as solid, or as dissolved in water?

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 ...
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  • 1,311
4 votes

Are humans capable of both anaerobic respiration, and lactic acid fermentation?

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 ...
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3 votes

Why are there so few multicellular anaerobes?

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 ...
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3 votes

Pyruvate as a final electron acceptor in the electron transport chain

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: ...
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3 votes

Need for two oxygen sensors in E. coli

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)...
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3 votes

ATP yield of fermentation: study to cite?

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 ...
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2 votes

Why would yeast grow but not produce alcohol?

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 ...
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2 votes

Are humans capable of both anaerobic respiration, and lactic acid fermentation?

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 ...
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2 votes
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Can a cell survive temporarily without oxygen?

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 ...
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  • 8,031
2 votes

Is there any organism that is born with all the nutrients and resources needed for their entire lifetime?

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 ...
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1 vote

Can storing food in a de-pressurized container result in anaerobic bacteria growth?

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 ...
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1 vote
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Is it possible to make anaerobic media too reducing?

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 ...
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  • 4,638
1 vote

Can nitrate be an electron acceptor for NADH generated in the citric acid cycle?

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
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1 vote

Facultative anaerobic organism

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 ...
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  • 2,048
1 vote

At what levels of muscle energy intake does catabolism start?

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 ...
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  • 5,595
1 vote

Why would yeast grow but not produce alcohol?

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, ...
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1 vote

Why would yeast grow but not produce alcohol?

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, ...
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