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Questions tagged [metabolism]

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

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Human metabolic pathways involving particular proteins

I am currently working on a project that involves analyzing the pathways in which certain proteins are involved. I have compiled a list of proteins, and I am keen to explore the pathways they ...
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Is the Electron Transport Chain a metabolic pathway?

In my textbook, I read the following description relating to the Electron Transport Chain (ETC): The metabolic pathway through which electrons pass from one carrier to another is called the electron ...
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Why would decreased temperature be associated with increased cell size, in deep-sea crustaceans (or in general?)

I was reading Wikipedia regarding deep-sea gigantism -- the fact that deep-sea species are often much larger than their shallow-dwelling counterparts. The article said, Decreasing temperature is ...
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What is the biological pathway for the biodegradation of DDT (pesticide)?

There are various micro organisms which can degrade DDT. Which micro organism is most frequently used for biodegradation of DDT and what is the metabolic pathway by which DDT is degraded?
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How many protons are pumped into the intermembrane space by Complex IV in OXPHOS?

According to Sazanov (2015), "to reduce oxygen to water, four 'chemical' protons are taken from the matrix side [...]. In addition, four protons are pumped across the membrane into the IMS". ...
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What is the difference between digesting sugar and carbohydrates?

To understand where I'm coming from, first some commonly distributed (mis?)conceptions: (Obviously to be taken with a big grain of salt because they are somewhat contradictory) Sugar is bad for your ...
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Which position do retro aldol reactions occur in (comparing glucose and fructose)?

Regarding glycolysis, my text states: What is the biochemical rationale for the isomerization of glucose 6-phosphate to fructose 6-phosphate and its subsequent phosphorylation to form fructose 1,6-...
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Water-soluble vitamins involved in amino acid metabolism in the citric acid cycle

I have never seen anything comprehensively written about the vitamins necessary to metabolize amino acids through the citric acid cycle and gluconeogenesis pathway other than the following diagram ...
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Metabolic significance of aspartate transaminase in mammalian liver

Aspartate transaminase (aspartate aminotransferase) is an enzyme that is abundant in hepatocytes and catalyses the reaction: (Modified from https://en.wikipedia.org/wiki/Aspartate_transaminase) There ...
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Why are "alanine, cysteine, glycine, and serine" not ketogenic amino acids? [duplicate]

In the figure below, Purple letters represents both glycogenic and ketogenic amino acids Brown letters represents glycogenic amino acids, only Green letters represents ketogenic amino acids, only ...
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Can humans metabolize D-malate?

Only the L-isomer is produced naturally, while racemic mixtures are produced synthetically and used commercially as food additives and energy supplements. So what happens when we consume D-malate? ...
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How to measure cytochrome P450 activity in owls?

I hope you're all doing well. I'm currently working on a research project focused on owls and their exposure to anticoagulation rodenticides such as brodifacoum. As part of my study, I need to measure ...
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Where is the source of H+ in the matrix that will be pumped during the electron transfer system? Where does the OH generated at that time go?

In the electron transfer system, it has been mentioned in prior questions that complexes I, III, and IV are proton pumps and that these pumps pump protons from the matrix into the intermembrane space. ...
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Fate of GTP produced in the TCA cycle

As someone already mentioned in one of the following questions, the TCA circuit generates GTP in addition to NADH and FADH2. The fate of NADH and FADH2 is clear: they are used to pump protons in the ...
Blue Various's user avatar
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What is the simplest known metabolic pathway?

What chemical process that can be defined as "metabolic" is the simplest found in any organism, and are there even simpler theoretical metabolic pathways, that are simpler than any found in ...
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Is the "endo-" prefix in "endotherm" inconsistent/opposite to its use in "endothermic reaction"?

It seems to me that the "endo-" in the biology term "endotherm" is opposite to the "endo-" in the chemistry term "endothermic reaction." Is that the case? As I ...
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Bi-phenyl degradation pathway in lignin

I am studying lignin - and really like the bi-phenyl degradation pathway of DDVA by SYK-6, as shown below But I can't find any literature on whether this pathway transfers from the dimer to the ...
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Why is sport healthy if high metabolism decreases life expectancy?

There is something that appears as a contradiction to a newbie like me. Sport is widely recognized as healthy and recommended by medical experts. Metabolic rate is inversely correlated with lifespan....
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Performing Flux Balance Analysis (FBA) or Metabolic Flux Analysis (MFA) on tracer metabolomic data

I have targeted tracer metabolomic data of a mammalian cell culture in 3 biological replicates, and 3 time-points (0, 10 and 60 minutes). Cultures were fed with 13C6-glucose. After manual curation I ...
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Why is iron transported across membranes in the ferrous form?

Iron in the diet of animals is predominantly in the ferric form, but it must be reduced to the ferric form by a specific ferrireductase before it can be transported across the cell membrane into the ...
Karthikeyan's user avatar
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What puts a lower bound on the size of warm-blooded animals?

The smallest known vertebrates are frogs that range down to 0.01 grams. I would take that as evidence that at smaller sizes an endoskeleton is more of a liability than an asset. 1-2 grams is a lower ...
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Recycling of nitrogen in hibernating mammals

Hibernating mammals are required to undergo profound changes in metabolism. In addition to the more studied requirement of providing energy, there are problems in relation to nitrogen metabolism ...
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Is ghrelin only secreted when the stomach is empty?

Several texts indicate that ghrelin is secreted when the stomach is empty. However, some(not all) texts also indicate that ghrelin is secreted when blood sugar levels are low. Is the second statement ...
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Does anaerobic glycolysis produce lactate or lactic acid?

I am not properly educated in biochemistry so I apologize if my question makes incorrect assumptions or uses bad definitions. I am confused about the seemingly interchangeable usage of "lactate&...
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Contrast Fluids in MRI: Which tissues "glow" first?

I am a bioinformatic and data scientist in progress, working on my Master Thesis about prostate cancer. Now I am at that point, I have a strong guessing, that contrast fluids in magnetic resonance ...
Allerleirauh's user avatar
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Glycemic Index and AUC Curve: why do two different foods have differing numbers?

The AUC Glucose/Blood Level curve Integral (area under curve) is used to calculate the Glycemic Index of certain foods. I have a question on why two sample foods with the same mass of carbohydrates ...
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Human Body's rate of conversion of carbs, protein and fat into energy?

I understanding there are some complicated processes, but I'm interested in generally how fast the body converts certain chemicals into energy and the period of time this conversion occurs. I'm ...
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Calculating the Glycemic Index using an AUC Glucose/Blood curve?

Does anyone know the mathematics to calculate the Glycemic Index using a AUC Glucose/Blood curve? Is there an article documenting the process? I understand that algebra and integral calculus is ...
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What prevents the diffusion of proton gradient in Gram (+) bacteria [duplicate]

The proton gradient in bacteria is important to power FTPase and flagella. How do Gram (+) bacteria maintain a proton gradient without a periplasm (Gram (-)) or intermembrane space (mitochondria). Why ...
Curious Student's user avatar
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What is the share of body energy that the brain consumes? Is 20% reliable?

"20% of the energy at only 2% of the weight" is a frequently regurgitated factoid. More precisely, it should read: 20% of oxygen consumption. The problem starts when one looks into the ...
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Why do highland/alpine plants require a drop in night temperatures to thrive?

There are mountain plants which require a drop in nightly temperature (many Nepenthes, Heliamphora and orchids for example). A non-specialist explanation is that the plants die of "starvation&...
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How does red light change the cellular mechanism in cells?

As winter approaches and the amount of sunlight decreases in the northern hemisphere, I have been reading about red light therapy and its supposed beneficial clinical effects. Yet there is no much ...
Evamentality's user avatar
2 votes
1 answer
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Where in the biological realm is vitamin B5 chiefly produced?

Can yeast produce pantothenic acid (vitamin B5)? Do bacteria efficiently produce it? Or does it only come from plants? The Wikipedia page for pantothenic acid doesn’t seem to answer the question (...
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Can organisms grow on acetic acid?

Can organisms grow on acetic acid and water (with <1%, all inorganic, impurities), i.e. using acetic acid as a carbon / energy source? If so which concentration of water would it start at? (...
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What is the conjugation capacity of the liver?

Our liver conjugates 250-300 mg bilirubin per day under normal circumstances but it is capable of conjugating much more. What is the upper end per day after which it won’t be able to conjugate leading ...
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How to Scale Metabolic rate and drug dosage according to Mass?

I was reading a book "Biology and evolution of Crocodilians" by Gordon Grigg and David Kirshner. And I can't understand the part about metabolic scaling no matter which method I tried I can'...
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3 votes
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Heart rate and Metabolic rate relationship

Metabolic rate in humans can be approximated using the Penn State equation. It can also be estimated using direct and indirect calorimetry. According to Kleiber's law, metabolism scales across species ...
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Does succinic acid provide any caloric value in humans?

Would the ingestion of pure succinic acid provide any caloric value in humans? I couldn’t find any nutritional information about it via Googling, but I read on Wikipedia that it’s converted into ...
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Do Mannose and Galactose yield the same products as Glucose when oxidized?

I just started learning about sugar metabolism, when I saw how other monosaccharides enter the glycolytic pathway. Mannose enters glycolysis as fructose-6-phosphate at the expense of 1 ATP, then ...
Josh Arceno's user avatar
2 votes
1 answer
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Are there irreversible metabolic reactions that can happen in opposite ways depending on the cellular conditions?

Irreversible reactions are thermodynamically irreversible, not microscopically irreversible. "Irreversible" here means the reaction happens "out-of-equilibrium". It is a ...
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Walking or running makes me consume 200 to 550 kcal/h, that's true, but always 68 to 72 kcal per kilometer whatever the effort done. Why?

My connected watch tells me that when : I'm walking I'm consuming 200 - 250 kcal per hour, running: from 500 to 550. and this is ok. But it also tells me, that how many kilometers are my trips, I'm ...
Marc Le Bihan's user avatar
2 votes
1 answer
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Is the pyruvate dehydrogenase reaction considered part of the Krebs Tricarboxylic Acid Cycle?

I’ve encountered questions where I’m asked to find out the CO2 released, the number of oxidative carboxylations etc. in the Krebs tricarboxylic acid cycle. I always include the pyruvate dehydrogenase ...
Lynn Mary's user avatar
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Do plants digest substances they ingest?

I was thinking about plants having no digestion system (is that true at all?) and my conclusion was that they only ingest substances that they can use like that or that they can transform into usable ...
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Adh2 promoter in saccharomyces cerevisiae

I'm looking at expressing a protein in saccharomyces cerevisiae using the Adh2 promoter. My understanding is that the gene will be repressed by the presence of glucose, but when glucose runs out it ...
Shreyas Patel's user avatar
6 votes
1 answer
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Does biofilm formation hinder photosythesis?

In photosynthetic bacteria such as Cyanobacteria, Synechocystis sp. PCC 6803, the bacteria need access to both light, CO2, and water to perform photosynthesis. However, in thick biofilm structures (e....
Anwar Elhadad's user avatar
2 votes
1 answer
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After digesting food, where does the energy go before being stored by the body?

I'm trying to piece together a simplified model on how the energy flows in the human body. From what I understand: We store enough ATP for around 2 seconds of maximum exertion We store enough ...
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Is Acetyl-CoA ever transported out of the cell, and in that case how?

Acetyl-CoA is sometimes formed as a result of protein katabolism. Certain cells (in the muscle for instance) can't use Acetyl-CoA to synthesize fatty acid. If there is no immediate need for energy, ...
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3 answers
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Why are 6 turns of the Calvin cycle needed to make one molecule of glucose?

I‘ve read that 6 turns of the Calvin cycle are required to make 1 glucose molecule. But, 3CO2 and 3RuBP are used in one cycle and 6 triose phosphate is produced. Only 5 triose phosphate molecules are ...
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How can we explain that glucose at its concentration less than a Km for the transporter enters the peripheral circulation?

I'm studying biochemistry from Kaplan's book. In it, I found the following paragraph in the topic on glucose metabolism: "GLUT 2, a low-affinity transporter, is in hepatocytes. After a meal, ...
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Do quantum mechanical effects such as uncertainty, tunnelling and entanglement play role in the electron transport system of respiration?

The electron transport system of aerobic respiration involves an extensive pathway of electron and proton transfer from one centre to another. Now, since they are quantum mechanical particles, shouldn'...
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