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Questions tagged [metabolism]

Metabolism is the set of defined biochemical transformations occuring within the cells of living organisms.

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Cause of Obesity

Considering the normal function of adipose tissue in sequestering 'persistent organic pollutants [POPs]', is there any evidence that the existence of such POPs within fat cells interferes with the ...
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283 views

Was lactose present in the environment before the evolution of mammals?

Are there lactose sources other than dairy products in nature? I tried to search for it but I did not find anything. The question arose because I was wondering whether lactose-utilising enzymes in ...
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Bacteria utilize short chain fatty acid as energy source

I'm doing research about the short chain fatty acid producing bacteria. I studied 7 short chain fatty acid (acetic propionic butyric isobutyric valeric isovaleric and captionic). and I found that the ...
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What happens to lipoprotein lipase after a sugar only diet?

Insulin increases the activity of lipoprotein lipase thay allows cells to take in lipids from chylomicrons in the blood. If a person takes a sugar only meal like drinking coke, insulin is released. ...
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286 views

Does thyroxine increase BMR or metabolic rate?

I know that thyroxine increases the metabolic rate, but my teacher said it increases the metabolic rate, not the basal metabolic rate, the basal metabolic rate is always the same. What's the ...
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971 views

ATP Hydrolysis to AMP in the Urea Cycle. What is the Free Energy Change?

How is the hydrolysis of ATP into AMP and PPi in making arginosuccinate equivalent to the hydrolysis of 2 ATP?
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114 views

Why are my calculations for O2 requirements of daily metabolism so far off?

When I attempt to calculate the O2 necessary for a day of metabolism at rest (for an imaginary average human) and compare it with the expected O2 consumed per day my results differ by a factor of 3. I ...
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174 views

Why can't humans use dietary citric or acetic acid as a primary source of energy?

As the Krebs cycle is involved with the conversion of food in to citric acid, why can't eating citric acid be used as a temporary primary source of energy - in place of fat/carbohydrate/protein?? It ...
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why is LPL (lipoprotein-lipase) down-regulated during fasting?

During fasting our body needs additional sources of energy and that's why triglycerides are broken down into fatty acids and glycerol. where fatty acids can be used to generate acetyl-coA and ...
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Is lysergic acid diethylamide (LSD) metabolized in the body?

Is LSD broken down into other compounds by enzymes or hormones? If so, at what point and where in the body does this happen? I researched several papers appearing in a google search, but unfortunately ...
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111 views

Is there any evidence that supports glycolysis in mitochondria or chloroplasts?

Glycolysis is known to be a part of cellular metabolism undergone by both eukaryotic and prokaryotic cells, whether under aerobic or anaerobic conditions. As the endosymbiotic theory states that ...
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338 views

Is there a point in our life when ALL the atoms from our childhood's body get replaced?

The evolutionary biologist and Oxford professor Richard Dawkins makes on his TED talk the rather interesting suggestion that we human beings, are in nature more similar to a wave than an object. In ...
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Simplest known form of aerobic glycolysis

What is the simplest known way that an organism performs aerobic glycolysis? In other words, what is the simplest known way known to convert glucose into $\ce{H2O}$ and $\ce{CO2}$, other than by ...
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Extra-mitochondrial conversion of Acyl Carnitine to Acyl CoA

Normally fatty acids in the form of acyl CoA are converted to acyl carnitine in a reaction catalysed by carnitine palmitoyltransferase I (CPT1), which is also known as carnitine acyltransferase I. ...
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95 views

Does minimizing hunger maximize weight gain?

Due to the "obesity epidemic," there is a lot of focus on the causes of weight gain. We typically talk about strategies to cause weight loss, but what about strategies to minimize/maximize hunger? ...
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83 views

Breeding mosquitoes at lower temperature

It is well known fact that, to slow down the growth of drosophila, they are grown at 18-19 degree Celsius. It helps in maintaining stocks for longer time without frequent change of food. Is it ...
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260 views

Negative Oxygen Consumption Rate

Oxygen consumption rate (OCR) is defined as the rate at which cells consume oxygen. I reason that for cells not capable of photosynthesis, OCR is strictly non-negative. That was until I read this ...
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360 views

How didn't large, highly active dinosaurs overheat?

The cube-square law seems to be the deciding factor when it comes to biological heat management. Small organisms with large surface areas relative to their volumes, like mice, need fast heartbeats and ...
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55 views

How much damage is caused by smoking 2-3 cigarettes on a healthy body? [closed]

I do not know how bad does 2-3 cigarettes on the average healthy body. I do not want to include genetic factors on this issue. So, maybe there is a study or something on this topic. Does it cause ...
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Do strictly anaerobic organisms use metabolic reactions requiring oxygen?

When looking through genome annotations of strictly anaerobic organisms I see reactions featuring oxygen. I suspect these are likely an artifact of the annotation process. But I am wondering if it is ...
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1k views

If during exercise the affinity of oxygen for haemoglobin is decreased, what are the general consequences for tissues?

During exercise more respiration occurs, and hence more oxygen is required. So the oxygen dissocation curve is shifted to the right. So at a given Oxygen partial pressure, the haemoglobin is less ...
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Kinetic mathematical model of glycolysis?

I am looking for papers containing kinetic mathematical models of glycolysis, hopefully in mammalian cells (or as close as possible, say yeast). The papers I have found do qualitative analysis (...
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Is burnt THC still psychoactive?

Asking from a more practical angle. If one smokes a joint - does the THC in the embers contribute to getting high - or is it only the THC released by the heat of the smoke in the not-burning section ...
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107 views

E. Coli metabolization of paracetamol

For my science fair project, I did an experiment on how paracetamol and ibuprofen affected the growth of bacteria. By day 5, however, parts of the paracetamol blackened (image below). I am wondering ...
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Regulation of Glycolysis and other pathways at ‘irreversible’ reaction steps

The hexokinase, phosphofructokinase and pyruvate kinase steps of glycolysis (1,3 and 10, below) are the only ones that are irreversible, and are also the steps where glycolysis is regulated. Is it ...
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108 views

Contribution of major nutrients to energy in the human body

What is the contribution of the major nutrients -- glucose, fat and protein -- to the human body's energy requirements, in normal conditions? For some tissues, the fuel preference is known ...
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Entropy increase or decrease in an reaction

My question is how would you tell if the product of an reaction has more or less entropy than the reactants? For example, in glycolysis, when glyceraldehyde-3-phosphate becomes 1-3 ...
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1answer
300 views

Can the Na+/K+ pump backwards to generate ATP?

The standard physiological direction of the Na+/K+ pump is to export 3 Na+, import 2 K+, and hydrolyze one ATP to ADP. Can it be driven backwards, importing 3 Na+, exporting 2 K+, and generating ATP? ...
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1answer
406 views

ATP stoichiometry of the Na+/K+ pump

The Na+/K+ ATPase pump exports 3 Na+ for every 2 Ka+ imported. This process is ATP dependent, but I have not been able to find how many ATPs are required in each translocation. What is the ...
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999 views

Why are there so few multicellular anaerobes?

There are a few documented cases of multicellular anaerobic organisms, but I can't see a reason for it to not be more common. On the contrary, it seems pretty useful to be able to create energy even ...
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37 views

What are the chemical characteristics of cofactors that functionally differentiate them from the side chains of amino acids?

Cofactors are essential for the function of many enzymes, such as NAD+ in the glycolytic pathway - I was wondering how the chemical properties of these cofactors allow them to fulfil their function ...
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1answer
43 views

What is the minimum caloric intake for a truly starving adult

What is the minimum caloric intake for an adult? I'm not talking about a healthy diet. There's plenty of advice on that. I'm wondering what the absolute limits of H. sapiens are. When there's a ...
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3answers
8k views

Why only 6 water molecules are formed in the aerobic degradation of glucose?

I am studying the aerobic degradation of glucose and it seems that for every glucose molecule we should obtain $\ce{10H2O}$ molecules. However, it is known that we only obtain 6. $\ce{C6H12O6 + 6O2 -&...
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Reason for conversion of glucose to fructose in glycolysis

In glycolysis, glucose is converted to glucose 6-phosphate so it can not diffuse out of the membrane. Then it is converted to fructose 6-phosphate. Why is this? Perhaps it makes it less stable so it ...
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Glycolytic non-oxidative pathway

I am currently digging in some books to understand the three major metabolic pathways involved in physical training. The most difficult one for me is the glycolytic non-oxidative pathway (also more ...
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How do marine mammals stay hydrated?

This is a question that has always bothered me. A quick internet search yields "metabolic processes" as the reason for how marine mammals obtain water, but what are those processes and why don't land ...
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281 views

Affinity for oxygen and carbon dioxide in animals

I'm currently reading Treatise on Invertebrate Paleontology (A) and don't understand the following fragment: The affinity for oxygen in lower animals is many times that in higher ones, whereas ...
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2k views

How much time can a human survive only drinking water and eating sugar? [closed]

If a person only drinks water and eats glucose, how long could they survive before getting any symptoms? When would the damage become irreversible? When would that person die from lack of minerals, ...
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How is the human oxygen absorption dependent on the concentration of oxygen in respiratory air?

I just wanted to calculate the theoretical time span in which I could survive (conscious) in my apartment without letting the air on the inside exchange oxygen/carbon dioxide with fresh air. During my ...
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1answer
371 views

What is the energy cost of an action potential?

As I understand it, ions flow down their electrochemical potentials through ion channels during a neuron's action potential. Otherwise, ion pumps work to restore and maintain the resting membrane ...
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38 views

Were Telomeres the Master Key to Abiogenesis [closed]

Knowing as we do now that all manner of complex organic molecules and viscelles/micelles form spontaneously in various environments, from hot vents perfect for basic hydrophobic H-C fatty acids and ...
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What chemical conversions are involved , and what's the name for the process, when the muscles use lactate as an energy source?

I understand that muscles do anaerobic metabolism, specifically, "lactic acid fermentation", which I understand produces lactate. I'm not asking about that process. What chemical conversions are ...
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3k views

Does Glycolysis produce lactate, or pyruvate?

EDIT- Somebody suggested that this is the same question as this, it isn't. This one is asking about the definition of glycolysis. That one was asking about the definition of fermentation. Does ...
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Why is carbon dioxide produced in alcohol fermentation but not in lactic acid fermentation?

From my understanding, alcohol fermentation takes place in yeast and lactate production takes place in humans. These two pathways take place only when there is insufficient oxygen, because the other ...
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4k views

Why doesn't glucagon promote glycogenolysis in muscle?

Insulin stimulates glycogenesis in both liver and in muscles. Epinephrine stimulates glycogenolysis in both liver and muscles. But glucagon stimulates glycogenolysis in liver only. Why is this so?
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Is agriculture really a net contributor of greenhouse gases?

A lot of scientific studies and credible sources indicate that agriculture is one of the major contributors of greenhouse gases. The exact numbers seem to vary a lot, I've seen everything from 8% to ...
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If your body can slow down your metabolism, why doesn't it do that all the time?

I've read that in cases such as in anorexia or a lack of food, the body slows down the metabolism to preserve the little food it does get. If it can do this, though, why doesn't it keep your ...
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289 views

Sex differences in response to food deprivation

This question was inspired by a casual conversation with friends the other night. Some of us had noted that women tend to eat smaller meals more often (snacks, fruits etc) while men eat larger ...
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Does hunger necessarily mean that we should eat?

People feel hunger sooner after they eat food that consists mostly of carbohydrates. For example, if someone eats a good portion of rice then most likely they will be hungry after a couple of hours. ...
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How can you gain 1 lb of bodyweight from eating less than 1 lb of food surplus?

A commonly referenced "fact" is that a caloric surplus of 3500 kcal is equivalent to a 1 lb gain in bodyweight. But I'm confused. If you get 3500 kcal worth of, say, fatty acids, which are 9 kcal per ...