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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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What is a coupled reaction and why do cells couple reactions?

I was wondering what exactly a coupled reaction is and why cells couple them. I read the wikipedia article as well as several others, such as life.illinois.edu but I still don't get it. Could ...
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Are carbohydrates an essential component of human diet?

Are people able to satisfy all the needs of a healthy diet without consuming carbohydrates? My question includes the assumption that a person has no health condition that would prevent them from ...
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What is/are the molecular differences between HDL and LDL cholesterol?

Why exactly is HDL-cholesterol good for us and LDL-cholesterol bad for us. It has been well-established that LDL-cholesterol is associated with atherosclerosis and that HDL-cholesterol helps remove ...
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Why are there so many medicinal plants?

Question Quite a few plant species can be used for medicinal purposes wiki. As an example, Filipendula ulmaria is rich in acetylsalicylic acid (aspirin). An allele that produces a substance which is ...
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What preceded ATP synthase?

ATP Synthase is ubiquitous throughout life on earth and so most probably evolved within the last universal common ancestor (LUCA) before that lineage diversified into the various kingdoms of life. ...
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Is there any use of CO₂ in human body?

We all know CO₂ as a waste product of metabolism . Does CO₂ have any helpful role , apart from having a role in pH of blood ?
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During starvation, does the human body do anything to prioritize which organs receive nutrients?

When food is scarce, the body slows its metabolic rate to conserve energy. Are there any other systems or processes that prioritize which organs receive nutrients?
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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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In humans what is the last metabolic process to cease after death?

After death which of our body's metabolic processes will continue functioning for the longest?
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How can haired mammals synthesize vitamin D?

The human body can synthesize vitamin D in the skin from cholesterol, when sun exposure is adequate. But how can haired mammals do it? Do not they need it?
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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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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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What is the molecular basis of hangovers?

Well, most of us have experienced the wonderful feeling of the dreaded hangover. How does it work exactly? I imagine it has something to do with dehydration but what are the underlying mechanisms? ...
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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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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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What is the energy consumption of the brain?

What is the energy consumption of the brain, and is there a difference in consumption when waking and sleeping?
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What mechanisms tell temperate trees when to drop leaves?

I've been looking around and cannot find a definite answer on what it is that tells trees to change their metabolism and drop leaves. I see that such activity is called Deciduous. What interests me ...
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Circulation through the liver in light of drug metabolism

I have a lingering question which stems from an answer that I gave to What hydrolyses aspirin within the digestive tract and blood stream? When a drug or any other substance is absorbed into the ...
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Do plants need O₂ to consume energy they've stored via sugar?

This question came up as I work my way through the answers to another question I just asked. My understanding is that plant photosynthesis looks something like this (though with lots more going on ...
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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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Why are many fruits sour?

Many fruits (like apples, berries, citrus fruits etc.) contain high levels of organic acids, especially malic acid and citric acid. Are there any evolutionary functions of those acids in ripe fruits? ...
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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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Why can't the brain and red blood cells use fuels other than glucose?

The question is rather straight forward: I have always been curious as to why, but cannot find an explanation online. I can imagine that the mechanism is different for each, but why does brain tissue ...
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If so many different hormones/molecules work by activating adenylyl cyclase, how do they have different effects?

It seems that many hormones and molecules work by activating adenylyl cyclase to convert $\text{ATP}$ to $\text{cAMP}$, such as adrenaline and glucagon. Both of these seem to bind to $\text G$ protein ...
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Why our body does not produce polyunsaturated fatty acids?

Our body does not produce two polyunsaturated fatty acids (PUFA): linoleic acid and alfa-linolenic acid. I am thinking reasons for it. Saturated fatty acids have more energy than unsaturated. ...
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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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How Does Green Tea Increase Metabolic Rate?

According to the article "Green Tea Supplementation Affects Body Weight, Lipids, and Lipid Peroxidation in Obese Subjects with Metabolic Syndrome", Green tea increases metabolism and fat loss: ...
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What is the purpose of gluconeogenesis?

The gluconeogenesis pathway seems quite pointless to me. I don't understand why an organism would want to spend energy to create a molecule that can then be metabolized again for less energy? The ...
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What causes muscles to generate heat on contraction?

I'm curious what the exact cause is of dramatic heat generation that comes along with muscle activity. Can anybody explain this in understandable language?
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How much energy do small spiders expend when they are just waiting for their web to vibrate?

Roughly speaking, a small, complex electronic circuit or IC might sit in "sleep mode" using a current of roughly 1 µA (e.g. 1, 2), thereby using roughly $3\times 10^{-6}$ Watts, and that ...
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Why is a magnesium ion essential for ATP activity in enzymic reactions?

The Wikipedia entry on Magnesium in Biology includes the following: ATP (adenosine triphosphate), the main source of energy in cells, must be bound to a magnesium ion in order to be biologically ...
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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 ...
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Is there a way to quantify in vivo cholesterol transport rates?

I have always had trouble grasping the physiology of lipoprotein cholesterol transport. The "standard" description found in the literature is that liver synthesizes cholesterol which is carried in "...
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How much does a human brain's metabolic rate vary? [duplicate]

Possible Duplicate: How does brain energy consumption depend on mental activity? Our brains consume about 20% of our energy when we're at rest. How variable is a human brain's energy consumption? ...
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How to relate human metabolic model reactions and cancer drug targets / reactome items?

Trying to find a way to take a cancer drug (from CancerDR, for instance) and infer the metabolic reactions that are affected by it in the Human Metabolic Model. Essentially, I would like to know ...
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Relationship between our microbiome and personalized nutrition

Recently, it has been asked whether there are 'metabolic types' between humans that can benefit from a sort of personalized nutrition. One answer suggested that one discerning factor could be the ...
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How long does it take for E. coli to shift feedstocks?

With our fermentations we're noticing that it takes an appreciable amount of time for E. coli (K12 variant) to change from being metabolically streamlined on amino acids to being metabolically ...
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Does mixing alcoholic drinks really make you more drunk?

There is plenty of anecdotal evidence ("beer after wine and you'll feel fine, wine after beer will make you feel queer") that mixing alcoholic drink types leads to a stronger effect, but I can't find ...
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How efficient is the human body at metabolizing food?

My friend and I were having a discussion over how "efficient" human digestion is. If a human ate a 1000 calorie hamburger, how many of those calories (how much energy) does the body process into ...
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How should I feed and keep an ant queen?

I have captured wandering ant queen. I guess she was just fertilised and was looking for a place to start a hive. I'd like to create my own ant hive in artificial environment. I unfortunately only ...
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Does THC excretion increase if urine volume increases?

In regards to the body metabolizing and excreting THC: if urination is increased as a result of drinking lots of fluids, does that mean that more THC is leaving the body? To rephrase the question, is ...
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How many, and how severe, are known single gene polymorphisms for obesity?

A fairly recent meta-analysis of studies examining the association between adult obesity and polymorphisms of the FTO gene (Peng et al., 2011). The paper looked at 59 studies and concluded that, "FTO ...
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Is there such thing as a generic “metabolic type”?

A while ago I picked up a book called "Eat right for your metabolic type". The book discussed the effects of the endocrine system on the overall shape and the speed of metabolism. The book outlined ...
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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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What is the mechanism of oxygen uptake in E. coli?

How does E. coli uptake oxygen? Most of the literature I found is concerned with response to oxygen level supplied in the medium, as opposed to how much is actually transported inside. Can they shut ...
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How do muscle cells synthesize glycogen?

Hexokinase enzyme is present in all cells (including muscle cells) and can be suppressed by excessive G-6-P product. So that's why in the liver, glucokinase can act on glucose without inhibition of it ...
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How does it make thermodynamic sense for photosynthesizers to turn CO₂ into O₂?

My understanding is that animal metabolism consists of exothermic reactions like $$\ce{C6H12O6 + 6 O2 ->6 CO2 + 6 H2O + energy}$$ This makes thermodynamic sense to me. Animals need an exothermic ...
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Breakdown of energy expenditure at the level of a single cell

The metabolic rate measures how much energy an organism expends over a unit of time. Its breakdown for the human body in terms of its functions is well documented : so much for the heart, for the ...
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Tracking of oxygen molecules in glucose oxidation

For this reaction, found in typical biochemistry textbook: $C_6H_{12}O_6 + 6O_2 \to 6CO_2 + 6H_2O$ I am interested in where do the oxygen atoms of $6O_2$ go. I think they go to $6H_2O$, but this is ...
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Where can I find a list of common enzyme cofactors and/or co-enzymes?

Where can I find a list of enzyme cofactors and/or co-enzymes, ordered by how common they are? For example, $O_2$, $H_2O$, $ATP$, $ADP$, $NAD$, should be ranked in the first places, because they ...