The set of chemical reactions that happen in the cells of living organisms to sustain life.

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Where do the H+ ions come from in light reactions?

In the light-dependent reactions of photosynthesis, H+ ions pass to the thylakoid space. Where do these protons come from?
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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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Is it possible to measure Secondary Bile Acid Kinetics?

Is it possible to measure secondary bile acid kinetic and flux measurements in vivo? Anyone have any experience with this sort of technique?
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100 views

Burning fat transferred from one part of the body to another

While doing some research on cosmetic surgery, I discovered that there are several ways of doing breast enhancements, one of which was using body fat. While I haven't researched this method, I assume ...
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22 views

MTHFR recessive alleles and B-vitamins

I know that being heterozygous or homozygous recessive for the MTHFR gene prevents that person from being able to process and use folate and B-12. It causes an unhealthy level of homocysteine to ...
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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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101 views

Why is iodine used for metabolic hormones?

Iodine and related biological iodine-carrying hormones are phylogenetically very old, at least according to Wikipedia. Humans use iodine as a metabolic indicator, as do axolotls and apparently most ...
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1answer
104 views

Can cats use ketone bodies as only source of energy?

I recall reading that much of the energy a cat produces from its food comes from proteins which I assume would produce energy via being catabolised into amino acids which in turn, if glucogenic, would ...
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94 views

Do mitochondria use ATP in order make another ATP from glucose?

Do mitochondria use ATP in order make another ATP from glucose, or does it use another source of energy to convert glucose to ATP?
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190 views

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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155 views

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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63 views

How does the human body use energy?

As far as I know the glucose gets processed from carbs and fats and as a result carbon dioxide, water and "energy" are released. The carbon dioxide and water are expelled by the body, and then energy ...
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Is body energy production and consumption cyclical?

If we look into how energy is produced by the humans, it always involves some kind of periodicity: fuel combustion rotates engines, water rotates turbines, nuclear chain reactions heat up water, which ...
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71 views

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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22 views

Beta oxidation of saturated fats

In my text book there is an example of a 18 carbon long fat and it says that it can run 8 laps of oxidation. I don't understand why it doesn't run 9? 2 are removed each cycle? Thanks.
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19 views

Cell energy consumption and food intake

I am wondering if each cell in human body starts consuming ten percent more energy, how much food one has to consume compared to normal intake?
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34 views

Do muscles still hold glycogen reserves if there is no carbohydrate input

Afaik skeletal muscles take glucose from the blood to store it localy as glycogen, to be used in the case of intensive exercise. Does this still happen if the calorie input is exclusively made up ...
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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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1answer
32 views

Does creatine-phosphate (CP) supplementation regenerate NADH?

I have the following facts: It is possible to convert ATP <-> creatine vice-versa. (ref - non scientific) CP supplementation protects against metabolic syndrome. ref1 ref2 Fructose digestion ...
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378 views

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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57 views

Does ale give less of a hangover than a lager?

I got into an argument surrounding beer type and hangover. Apparently there is a opinion that ales give you less hangover than lagers do (considering same alcohol content consumed). My understanding ...
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317 views

Why gluconeogenesis?

It seems quite pointless to me. Why would I want to use energy to create a molecule that I can then use again for less energy? It seems only to serve as a complete waste of energy to me? Can someone ...
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34 views

How are ketone bodies used?

While searching for literature on ketone bodies, I can only seem to find how they are synthesized, but not how they are broken down. I'm looking for the series of events with enzyme names and ...
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1answer
48 views

Why use creatine phosphate?

We use creatine phosphate as an energy storage to resupply ADP with a phosphate group as our muscle cells only contain about 2-5 mM ATP. But why doesn't the muscle cells just keep 20-30 mM ATP instead ...
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35 views

Why doesn't the body optimize how many fatty acids it burns?

Ketone bodies are produced due to an excess of fatty acids being burned (accumulation of acetyl-CoA) so my question is: Why doesn't the body simply regulate how many fats it burns so it doesn't have ...
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Cholesterol's role in lipid uptake [closed]

I'm studying the digestion of fats and I understand that our dietary fats mostly consist of triglycerides. We absorb the fats and eventually they end up in a muscle/adipose cell for storage (as ...
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558 views

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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144 views

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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66 views

How is excretion of metabolic wastes from a cell related to its size?

As with anything that is taking place within a cell, the metabolic waste too must be proportional to the size of the cell. In particular the surface area to volume ratio. But how is the waste ...
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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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Energy metabolism in Cancer cells

The TCA cycle intermediate Isocitrate dehydrogenase commonly undergoes point mutations in cancers. This allows IDH to reduce a-Ketogluterate to 2Hydoxygluterate, causing a reduction in pVHLs ability ...
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242 views

What do trans-fats do when in human body?

Trans fats cause health problems, especially to the heart. https://en.wikipedia.org/wiki/Trans_fat#Health_risks My guess is that all effects happen because trans-fats are inherently toxic as the ...
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28 views

Mitochondria variability per tissue in humans?

I would like to know the distribution of mitochondrial content per tissue type in humans. I understand the simple metric that energetically active or energy requiring tissues will have more ...
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77 views

What is the relationship between protein-protein interaction networks and metabolic networks? [closed]

I am trying to find out how these networks can be linked together. I know that Protein-protein interaction networks and metabolic networks both fall under the Intra-cellular type of biological ...
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672 views

Is lemon water an alkalizing agent in the body?

I was recently having a discussion with someone about whether lemon water actually increases the pH of your body (by which I assume they mean the blood); their claim was that once Citric acid was ...
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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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114 views

Why do plants produce so much more sugar than they use?

I recently asked the question, "Do plants need O2 to consume energy they've stored via sugar?" to which @canadianer responded, "Yes, plants require oxygen to generate ATP from sugar. However, they ...
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1answer
24 views

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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363 views

Why are there so many medicinal plants?

Here is wikipedia page containing a list of plants used in herbal medicine. One might first want to argue that many of them actually do not have any medicinal/beneficial effect on heatlth. I think we ...
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36 views

Metabolism of different saccharides

Learning about carbohydrates, I wonder what the differences there are in terms of metabolism, and overall health between the different types of saccharides. In other words, does the body use ...
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299 views

During famine, does the human body do anything to prioritize which organs receive nutrients?

When food is scarce, the body slows its metabolism. Are there any other systems or processes that encourage prioritization of organs?
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32 views

How to measure heat loss in Tardigrades

I want to measure metabolism in tardigrades (a jar of 30 tardigrades). I know that an easy way to measure metabolism is heat loss; I can just measure the temperature of the water before and after a ...
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19 views

Which biosynthetic pathways take place in the plastid and were are they located?

I know that the isoprenoid, jasmonate, glucosinolate, fatty acids, chlorophyll, starch, and aromatic amino acid syntheses are located in the plastid. But I don't know if they are located in the ...
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Does the metabolic rate determine how fast the telomeres shorten?

In many papers one can read that telomeres may play an important role in longevity. According to Calado et al.1 the telomeres of mice are much longer than the telomeres of humans. However, mice have ...
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113 views

How did people who were living far from the sea obtain iodine during the Middle Ages?

Knowing that today iodine comes either from fish products or (artificially) enriched table salt, how did people who lived far from the sea survive before (especially during the the Middle Ages)? Edit ...
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58 views

How to measure metabolic rates of microscopically small animals?

I want to measure metabolism rates in Tardigrades Metabolic rates will be assessed immediately following their exit from cryptobiosis (an animal dormant state). I know that oxygen levels is the ...
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67 views

How does the body “know” how to metabolize foreign substances

As a freshman biochemistry major, I find myself befuddled by our body's ability to perform complex chemical reactions to break down foreign substances. I can see how we would evolve explicit pathways ...
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What is the biggest facultative anaerobic metazoan known to science?

Related: What's the biggest obligate anaerobic organism discovered till now? I had always assumed that the Riftia tube worms were obligately anaerobic since they lived next to anoxic volcanic ...
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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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Why is the Krebs cycle considered a part of aerobic metabolism if molecular oxygen is not involved in any of the reactions in the cycle

Why is the Krebs cycle considered a part of aerobic metabolism if molecular oxygen is not involved in any of the reactions in the cycle? I originally thought that Krebs cycle was aerobic metabolism ...