Questions tagged [metabolism]

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

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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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Could the Warburg effect be used to starve cancer cells in situ?

What is wrong with the following chain of reasoning? Nearly all cancer cells rely on high rates of glucose uptake (upto 200 times more than normal cells). This is known as the the Warburg effect. ...
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Statistical method for characterizing the relationship between body mass and metabolic rate

There is a dataset that contains body mass ($x$) and metabolic rate ($y$) from many different organisms. It is common to fit the data to the model of the form $y=ax^b$ and estimate the parameters $a$ ...
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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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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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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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Is there evidence to suggest that sleeping requires more energy than watching TV?

I have heard the claim: sleeping requires more energy than watching TV. I have heard the counter-claim - watching TV requires large amounts of energy. My question is: Is there evidence to ...
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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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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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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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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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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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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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What is the ultimate source of ADP/ATP in humans?

I am teaching myself Cell Biology from the internet. Despite my usually good Googling skills, I'm stuck in a loop with this question. Q: What is the source of ATP? A: ADP Q: What is the source of ...
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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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Normal TSH Levels in Hyperthyroxinemia

When it comes to hyperthyroxinemia, how is it possible for TSH to be normal when there is an elevated thyroxine concentration? What I know so far is that it is caused by a mutation in the Human serum ...
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Grapefruits and CYP3A4

Grapefruit juice contains furanocoumarins, which irreversibly inhibit CYP3A4. For this reason, when one is taking certain medications it is necessary to not eat grapefruits because the inhibition of ...
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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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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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Why are mammals unable to produce Essential Fatty Acids?

Why do we have to get them from our diet, and if they aren't taken in our diet we will face disease? Then why we don't have the enzymes which are require for EFA synthesis?
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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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Origin of the biochemical term, Pi (inorganic phosphate)

I would like to know when the term Pi (inorganic phosphate) was introduced in the representation of biochemical reactions, how it was originally defined, and the justification given then for using it ...
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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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Why isn't the phosphoglycerate kinase reaction of the glycolysis pathway irreversible?

Step 7 of the glycolysis pathway is the conversion of 1,3-bisphosphoglycerate into 3-phosphoglycerate by the action of the enzyme phosphoglycerate kinase, resulting in the production of 2 ATP ...
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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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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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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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Should we induce fever to assist healing?

I am currently reading "The Fundamentals of Anatomy Physiology" 10th edition, and have found it an incredibly interesting book. I have just been reading about the lymphatic system, and the various ...
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Why are my faeces black in color after eating Oreos

Why are my faeces black in colour the morning after I eat some Oreos? Day 1 : Eat a handful of Oreos & the next morning your stool is black. Day 3 : Eat a handful of cocoa flavored biscuits &...
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At what levels of muscle energy intake does catabolism start?

From my own reading, there are three ways used by the body to produce energy: Alactic anaerobic (direct degradation of ATP and creatine phosphate for regeneration of ATP) Lactic anaerobic (breakdown ...
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What is the brain's preferred energy source? Glucose or ketones?

As with all cells in our body, I know that the brain can get fed from both glucose and ketones, so my question is, given both of them, which one would the brain prefer to utilize first?
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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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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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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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Would short term increases in oxygen lead to beneficial effects?

After some thinking, I am wondering if having a 30% atmospheric oxygen concentration (or some other concentration) for a short time would increase the regeneration of energy in a body? It seems like ...
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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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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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Why is alcohol purged from the body more slowly when we sleep?

It is a popular belief that when you get asleep after drinking alcohol, in the morning you have higher level in your blood than if you stayed awake the whole night. Is this true? If so, why? Is it ...
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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 ...
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Is it wrong to consider an allosteric inhibitor a non-competitive inhibitor?

Supose Caspase-1 is allosterically inhibited. Since the inhibitor is not binding in the active site but instead in the allosteric binding site, can I conclude it is a non-competitive inhibitor?
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Is ATP produced in a different manner during glycolysis from that generated by the Krebs Tricarboxylic Acid Cycle?

The ATP in glycolysis is produced in the cell cytoplasm but that from the Krebs Cycle is produced in the mitochondria. The mitochondrial membrane contains an ATP-synthase protein complex that ...
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What is the fate of NADH produced in the liver during oxidation of lactic acid?

NADH (‘reduced NAD’) is produced during the oxidation of blood lactate in the liver. Glycolysis requires NAD+ (‘oxidised NAD’), whereas gluconeogensis requires NADH. However the NADH is apparently not ...
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In Japan, the official average body temperature is 36.0 °C. Why so different from that of Europe?

The Japanese Wikipedia states that the average human body temperature is 36.0 °C (here,"ヒト"). The statement references the data from the Japanese government. Actually all of my Japanese friends think ...
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How can grass-fed livestock generate fat?

How can herbivorous cattle get fat? These animals eat only grassy substances, think of cattle, buffalo, goats etc. For example, wheat grass contains 0% fat, and its nutritional value is limited to ...
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Violation of the law of energy conservation between photosynthesis and respiration?

For the production of one glucose molecule in the Calvin cycle a plant uses 18 molecules ATP, but when the same glucose molecule is oxidised — first in the cytoplasm and then in the mitochondrion — it ...