Questions tagged [metabolism]

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

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250 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 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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Can animals make their own unsaturated fatty acids?

I know that animals can't make poly-unsaturated fatty acids (PUFA) and so require them from dietary sources. For eg.Omega -3 and Omega 6 fatty acids. My questions : Can animals synthesize other ...
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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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Why is glucose our primary source of energy?

Is there any evolutionary reason for glucose being the "main" molecule used as a source of energy, beginning with glycolysis and subsequently cellular respiration (after being converted to two ...
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550 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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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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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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Why is the brain dependent on glucose?

The strict dependence of the (human) brain on glucose has always been puzzling to me. While ketones can substitute for a portion of the brain's energy needs, it cannot substitute completely: blood ...
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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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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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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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1answer
448 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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411 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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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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395 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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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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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 ...