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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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2answers
9k views

Why isn't acetyl-coA an entry point for gluconeogenesis?

The process of gluconeogenesis starts from various possible precursors - plausible entry points like, Pyruvate, OAA, Fumarate, Propionate (as succinate) and alpha-KG. It is important to note that, ...
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1answer
279 views

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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1answer
74 views

What are the obstacles to “refitting” the human body's metabolism?

As a layman, I understand the problem of rising obesity like this: In the old times, humans could never get enough food, thus they would eat whatever they could get. This "program" is encoded in our ...
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1answer
89 views

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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3answers
983 views

Requirement of energy for metabolic processes

Sorry if this is too elementary, but can someone explain why the following reaction can occur without a net influx of energy from some other process? $C_6H_{12}O_6 + 6O_2 \to 6 CO_2+6H_2O$ And why ...
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1answer
988 views

Relative roles of ATP and NADPH in anabolic and other processes

Chemistry isn’t my strong point, but I’m trying to understand why NADPH is said to be the main agent necessary for anabolic reactions, and if NADPH is used for anabolic reactions what is ATP used for? ...
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1answer
87 views

At what total rate is water used in metabolic processes over the entire biosphere?

A recent column on "The Straight Dope" website discussed the idea that water molecules are largely cycled around through the water cycle, and that therefore the water molecules that come out of your ...
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1answer
87 views

Rate of production of enzymes in human [closed]

In the metabolic pathways, each of the reaction needs an enzyme(protein) in order to occur successfully. Is there any quantitative measure that can be associated to this enzyme? Like synthesis rate of ...
2
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1answer
65 views

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 ...
5
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2answers
1k views

What is the source of the electrons generated in the Krebs cycle?

In the Krebs cycle, where do the hydrogens and electrons that NAD+ and FAD accept come from? It seems that citric acid only loses two hydrogens because it starts out with eight hydrogens and then ...
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0answers
131 views

What would the presence of a hub metabolite in a metabolic pathway signify?

Say I have a metabolic pathway, consisting of multiple metabolites and reactions. On analyzing the pathway I find that among all the metabolite, one metabolite is the hub metabolite (hub metabolite is ...
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0answers
45 views

Co-dependency between carbohydrates, fats and protein in the mammalian diet?

Following up from the question Are carbohydrates an essential component of human diet? I am interested in knowing more specifically how carbohydrates, fats and proteins are linked in the mammalian ...
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2answers
74 views

How did scientists establish the reactions that occur in metabolism? [closed]

How did scientists establish that macromolecules like proteins, carbohydrates and lipids are synthesized from other molecules with intermediate products by living cells. Did they observe this under ...
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1answer
90 views

Is there a certain environment where all cellular functions (or at least some) increase their rate?

Is there a certain environment in which all the functions (or some) inside a cell increase in their rate? Would the increased rate cause any damage to the cell?
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1answer
1k views

Are there known functions of AST, ALT, and amylase in the blood?

A number of enzymes can be measured in the blood or plasma that aid in the diagnosis of certain diseases. For example, patients with particular liver diseases may have elevated aspartate ...
5
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1answer
4k views

Why is the Pentose Phosphate Pathway so active in erythrocytes?

Is it because glyceraldehyde -3-phosphate (a molecule which when enter glycolysis help produce ATP through substrate level phosphorylation) can be prepared without losing an ATP through this process?
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4answers
5k views

What is the actual storage form of energy in muscles? ATP or Glycogen?

I was asked this question in my latest exam. I think the answer is Glycogen because ATP doesn't store energy for a long time so it isn't the ACTUAL storage of energy. Some classmates argue that in ...
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2answers
875 views

Energy coupling between two spontaneous reactions?

This diagram describes energy coupling between a nonspontaneous reaction (the formation of glutamine from glutamic acid and ammonia) and a spontaneous reaction (the hydrolysis of ATP). I can see that ...
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2answers
11k views

Where do transamination and deamination take place?

The only information I know is about deamination is that it occurs in the liver and kidney. But in which part of the cell does deamination occur? To which tissues is transamination specific, and in ...
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0answers
508 views

Can the respiratory quotient be calculated from a formula or must it be measured directly?

I found the following question on the Respiratory quotient: A normal human diet has a Respiratory quotient (RQ) of approximately 0.85. Given that pure oxidation of fatty acids has a Respiratory ...
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0answers
46 views

Validity of measurements of respiration in isolated mitochondria

I've recently read a couple of papers on exercise and mitochondria, in which state 4 and state 3 respiration rates and ROS production are assessed in vitro after exercise has been performed (i.e., rat ...
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1answer
45 views

Do I have to chew for digestion to kick in?

Liquid nutrient-rich products (such as Soylent) are consumed without chewing. But if I have to chew to initiate digestion, are those nutrients really "processed"?
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2answers
187 views

Where do plants obtain the metal ions needed for biological processes?

Enzymes employ metal ions (e.g. Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn) for catalysing certain reactions. Let's consider planting a seed. Where will it obtain these metal ions from? Just from water?
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1answer
119 views

Term of the type xxx-troph for a compound not used by an organism

A prototroph for compound X can make it A bradytroph grows faster if X is scavenged An auxotroph needs to scavenge X A hyperauxotroph lacks both the biosynthetic pathway and the transporters for X ...
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0answers
130 views

Insulin and leptin action on Anorexigenic Neurons in Hypothalamus?

Receptors for Insulin are present on liver, adipose tissue and muscles. In addition, there are Insulin Receptors present in arcuate nucleus of hypothalamus, which influences anorexogenic neurons ...
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1answer
372 views

Why are both glucagon and cortisol released in hypoglycemia?

Cortisol is released in response to prolonged stresses; one situation when cortisol is released is when blood glucose level is low. In this situation cortisol acts on adipose tissue promoting fatty ...
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1answer
2k views

Fate of Acetyl CoA in well fed state?

When we have eaten well and take fat rich diet then in this condition Acetyl CoA produced from fatty acid breakdown will be gone to storage in adipose tissue or not? If it will go for storage then why ...
3
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1answer
706 views

What is the substrate for glycogenesis?

In glycogenesis (i.e. the synthesis of glycogen), are sugar phosphates the direct substrates for glycogen polymerization? I would certainly think so since glucose is phosphorylated and then stuck onto ...
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1answer
539 views

Thyroid hormone metabolism and excretion

My understanding is that hormones generated by the thyroid gland, including, for example, T4, are excreted and recirculated in the body through the digestive tract. The reason for thinking this is ...
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1answer
377 views

Why does cold kill humans but not bacteria? [closed]

Bacteria can continue like nothing happened after being exposed to low temperatures why doesn't this happen to humans as well? Why can't our metabolic machinery continue as normal?
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1answer
1k views

What's the highest glucose concentration (in mM) anywhere in the human body (tissue, capillaries, tumor microenvironment, etc.)?

Glucose blood levels are around 5mM, or 10mM after meals. In capillaries these levels can rise by about 40 %. I haven't found measurements of glucose concentration in tissues, or in extracellular ...
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0answers
20 views

Could there be some safe, hypothetical way of turning on and of thermoregulation?

This is something I thought of with the whole artificial gill concept. Could a modification to the brain/nervous system allow a human to turn off their thermoregulation in air/water of the right ...
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1answer
2k views

Can lactate be created in ketosis?

After looking at Cori Cycle (from wikipedia) I have a question about how the lactate can be produced in ketosis. According to this article: in a low-glucose state, where the body senses that ...
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1answer
91 views

Does the body prioritise the use of available sugar before fat?

Let's say you eat a very unhealthy snack that contains 90% sugar and 10% fat. Would somatic cells not start using the fat for energy until all the sugar is used up? Does the body not use fat at all ...
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1answer
119 views

Bilirubin metabolism and UGT1A1 inhibition in human vs. monkey?

In human UGT1A1 seems to be the only relevant enzyme to glucuronidate unconjugated bilirubin into excreted forms. Is the pathway the same for e.g. the Cynomolgus monkey (Macaca fascicularis) in vivo? ...
4
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1answer
169 views

How can I obtain a computer readable model of Dr. Gerhard Michal's biological pathways map?

I want to run simulations of various metabolic pathways – the project could end up becoming quite large, and having a machine readable chart would make thing a lot easier. Does anyone know if there is ...
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4answers
3k views

Where do the four ADPs come from in the second stage of glycolysis?

In the first stage of glycolysis, the two molecules of ATP are broken down into 2 ADPs + 2 Pi through hydrolysis, then in the second stage of glycolysis they are phosphorilazed to obtain 2 ATPs. How ...
5
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1answer
125 views

Cellular demand for antioxidants

Antioxidants such as ascorbate and glutathione serve to inactivate radicals and counteract spontaneous oxidation reactions, such as unwanted disulfide bonds in proteins. These systems are cycles, ...
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0answers
38 views

Anaerobic nutrient expenditure

Doing some research into different forms of exercise and energy systems and I realized something odd about the way we talk about energy. When we eat, we take on macronutrients that are broken down ...
5
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1answer
134 views

How are ions 'pumped' across a membrane during electron transport?

A number of sites (including this one) that provide descriptions of photosynthesis state that high energy electrons 'pump' ions across a membrane. What is the actual 'pumping' mechanism? I've looked ...
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0answers
41 views

Need to solve a “pseudo-metabolic” network for rates

following problem: I have data on a certain complex association network (from monomers 1 ... 8 to complexes of all combinations, such as, 12 ... 13 ... 18 and so on until 12345678, so that I know ...
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0answers
105 views

Are there animals that can deliberately manipulate their metabolism, apart from hibernation?

Are there animals that can slow down their metabolism deliberately? I know that hibernation would be one mechanism, and maybe being cold-blooded, but I was wondering if there was maybe an animal that ...
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1answer
1k views

What is ATP and why is it said to be a source of energy? [closed]

Is ATP a molecule or a kind of energy. When I studied the active transport, it's said the ATP would release energy to change the carrier protein shape. So confused. Thanks for your help.
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0answers
86 views

Is it possible to stimulate the EPOC process?

On Wikipedia, EPOC is defined as: Excess post-exercise oxygen consumption (EPOC, informally called afterburn) is a measurably increased rate of oxygen intake following strenuous activity intended ...
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0answers
24 views

Bilirubin metabolism pathway in non-human primates (NHP)?

In human UGT1A1 seems to be the only relevant enzyme to glucuronidate unconjugated bilirubin into excreted forms. Is the pathway the same for e.g. the Cynomolgus monkey (Macaca fascicularis) in vivo? ...
4
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1answer
133 views

Why does our body regulate metabolic processes using the thyroid hormone?

People with hypothyroidism do fine when taking medication containing their daily dose of thyroid hormone. This means that the signaling function of the thyroid hormones is, in principle, unnecessary. ...
2
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1answer
636 views

What are calories and how to burn them? [closed]

What exactly is a calorie? When burning calories, do we always lose fat? I have tried many apps to measure calories, do they give exact amounts? How many calories should be taken a day?
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0answers
495 views

If chylomicrons can not get into the capillaries, how do they supply to tissues?

The transport of chylomicrons is into the lacteals mainly because they are too big to get into the capillaries and yet they later supply triglycerides in the extra hepatic tissue by traversing in the ...
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1answer
81 views

Why does protein kinase C activated by different means have different effects?

I could be way off base but I think I remember learning that Protein Kinase C has some effects when activated by one pathway and other effects when activated by another. How does this happen? Is it ...
2
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1answer
403 views

How many calories do gut bacteria burn?

It has become well-accepted that microbiota of the gut (a.k.a. gut bacteria) consume calories that are ingested and can have significant effects on energy metabolism in humans. For example, if you ...