14

Is there a significant difference in calorie burn? No. The brain, while only making up 2% of our body weight, accounts for ~20% of our energy use at rest. That's because the brain, being critical for survival, is a very high-maintenance organ. At rest, the membrane potentials of all neurons - firing or at "rest" - need to be controlled/maintained. Of all ...


11

This is a common phenomena which most of us come across. Seeing flashes of light, stars and other shapes in the eyes occur when the body goes through stressful activities. For example while you are climbing the blood flow will be more to other prominent parts like hands and lower waist so brain and eyes will get less supply of blood as well as nutrients. ...


10

They don't eat little. Consider the volume of milk / food they consume as a ratio of their weight. Quite the contrary they are ravenous machines and their consumption is much higher than an average adult. All cellular energy comes from the hydrolysis of ATP, and the production of ATP comes from the breakdown of glucose. The glucose comes from a sugar found ...


10

I agree with @inf3rno: caffeine is a stimulant that acts on the brain and various other parts of the body (Snyder et al., 1981) and I wish to elaborate on its psychopharmacology. Caffeine's effects in the brain are mediated through adenosine A1 and A2 receptors (Daly et al., 1983). This results in a variety of actions (Fredholm et al., 1999). Most notably, ...


7

Just to add to the answer from @buzrw: Using data from here and here I have estimated recommended calorie intake per kg for a 2 yr old and for an adult. I've used figures for males and assumed 70 kg for the adult weight which is the "international standard man": toddler: 120 Cal kg-1 adult: 40 Cal kg-1 So yes, the energy intake of toddlers is ...


7

First, it might be helpful to talk briefly about what heat is. It is a form of energy - molecular energy. Basically, heat is the amount of jiggliness of the molecules of a substance or object. When we look at a hot object, it doesn't apear to be moving any more than a cold object, but on a scale much smaller than we can see, it's molecules are moving faster ...


7

I don't have the math at hand for the actually energy efficiency, but let's just start from the storage capacity. Basically, an electric eel wouldn't make a very good battery. They could be a decent, albeit fairly inefficient capacitor, but they actually store little energy. Using data from Wikipedia on Electric Eels it works out to something less than 2 ...


7

There are no known life forms that use mechanical energy as a primary form of metabolic energy (i.e., for generic cellular functions). Many life forms are sensitive to mechanical disruption in some way, so they do utilize mechanical energy, but in a very limited fashion (@David's answer touches on this), and of course many organisms have life cycles that ...


6

I was musing on this and did some strange googling, and have some ballpark figures for a bunch of different organisms. It's far from a complete answer but it's at least a start, and all this won't fit in a comment. DNA replication, I assumed, was a huge metabolic drain on the cell. Turns out that is far from the case. Many helicases are passive, requiring ...


6

Caffeine is a stimulant, which helps you release the energy your body stored. Caffeine is a central nervous system and metabolic stimulant,[12] and is used both recreationally and medically to reduce physical fatigue and to restore alertness when drowsiness occurs. It produces increased wakefulness, faster and clearer flow of thought, increased ...


6

It is not possible to do this directly. Indirectly, it is possible, this is actually done by harvesting fruits - they contain the energy of the sunlight conserved in chemical compounds like sugars or starch and their cellular structures. The basic process for this is photosynthesis. The products from the fields are used technically to produce gas by ...


6

I'll give it a layman's attempt in sort of an "ELI5" approach. I hope the analogy isn't too simplistic, and please don't take it too literally. How do plants use K+? Plants control K+ concentrations and do work within the plant by pumping K+ between different compartments. Because water tends to follow solute concentrations (osmosis), plants can do things ...


6

This is definitely not my field, and I have no interest in science fiction, but the question struck me as interesting, and brought me to an area of bimolecular science that may be relevant to the question. First, in direct answer to the question, I do not know of any examples of life forms of the type you suggest. However there are examples of biological ...


6

Summary It is the nature of the biochemical reaction that determines whether a reaction of ATP involves hydrolysis of the β- or γ- phosphoanhydride bond. If a part of the ATP molecule is incorporated into one of the products, the choice of bond to be cleaved emerges from the chemistry of the reaction. If the hydrolysis (with a negative free energy change, ΔG)...


5

Viruses hijack the hosts translational machinery, forcing the host to downregulate translation of other proteins in favor of viral proteins. Your cells will eventually lyse, but in the meantime they would not be producing the enzymes required to make whatever product it is you're trying to get, likely resulting in low yields that are contaminated with virus.


5

I think there are a few principles that we need to consider before answering your question. (a) When a reaction is at equilibrium, the rate of any elementary reaction is exactly balanced by that of the reverse process. This is an important one. The above principle follows from transition-state theory, which holds that the activated state for the reaction ...


5

The most basic example of what I would like to talk about seems to be the algae powered lamp that has (apparently) been developped. I think you misunderstood the idea. That lamp uses bioluminescence and not electric power. Normally living cells don't like to give you energy. The trick we use is anaerob fermentation. Without the presence of oxygen (good ...


5

In endothermic and ectothermic animals, ie. warm and cold blooded animals, metabolic rates are inversely proportional to size of the organism. Quoting from https://www.biog1445.org/demo/04/metabolicrate.html This is because smaller animals have a higher surface-to-volume ratio, thus a larger relative heat loss to the environment per unit time. To ...


5

This is an interesting question (I really mean this — see below), for which a straight answer is remarkably difficult to find on the web. When I googled for it I got pages with statements that obligate anaerobic bacteria still had the electron transport chain (ETC) and ATP synthase as there were different electron acceptors other than oxygen. Yes, we know ...


4

Gains heat; humans are not particularly well-adapted to make use of heat as an energy source. In a simple matter, if something you eat is hot when it goes in then the average temperature of the body has increased. More relevantly (and to get this more on-topic for biology), eating anything will generally increase your body temperature, as in order to ...


4

Would the body use this transferred fat for as energy, or would it ignore it as it wasn't stored there in the first place? It would use it as energy source, there is no such thing as "ignored tissue". Fatty acid mobilization is regulated by epinephrine and insulin. These are hormones which are ofc. carried by blood, so every white adipose (fat) tissue is ...


4

This is oversimplified, but hopefully clear. When we eat food, metabolic processes break down larger, multi-carbon molecules (like glucose) into smaller molecules. This process is called catabolism, and it releases energy. Here's a simple example of a catabolic reaction: AB -> A + B + energy For more on this principle, look at the section on Le ...


4

Yes, the energy from ATP hydrolysis can vary between different cell types and condition, because it depends on several factors. Hence, you will find different values in various textbooks. First, like any chemical reaction, the free energy $\Delta G$ of ATP hydrolysis depends on the concentrations of the reactants. You can explore different values of $\Delta ...


4

A few explanations at the cellular and molecular level: First, for contraction to happen, muscles need signals from nerves. Replenishing the pool of neurotransmitters (used for each synaptic burst) takes a bit of time, and short-term exhaustion may happen at this level. In the muscle cells, contraction is caused by a calcium release within the cell, from ...


3

A year and a half later, I stumbled upon this article by Ars Technica. To summarize, research/experts acknowledge that the calorie system is a poor way to measure human metabolic performance. Gut fauna, calorie measuring device differences, and caloric differences produced by different levels of cooking all contribute to this system being unreliable. To ...


3

I suspect that what you are actually looking for is the following: - 1 gram of fat = 9 kcal - 1 gram of protein = 4 kcal - 1 gram of sugar = 4 kcal - 1 gram of alcohol = 7 kcal Those are general and inexact values. They're just often used to give a rough idea of the amount of energy we get from different types of food.


3

I'm pretty sure this doesn't exist. If it did, that would be awesome. The following is 100% pure speculation with nothing to back this up at all (as a disclaimer). Phosphorus-31 (the stable isotope) is NMR active, which means that you could theoretically use an MRI machine to visualize phosphorus. A quick google search shows scientists attempting to use ...


3

I think the poster wants only a simple answer, so I am going to answer in simple terms. The fates can be - 1 Used in cellular respiration as fuel and some amount can be converted to useful energy which can be used to build other substances and some energy can be lost as heat. 2.The animal can become prey for other animal. 3.The animal throws away some ...


3

In the absence of unanimous consensus and sources regarding the actual distribution of these shuttles,(wikipedia favours G3P shuttle abundance) let me try to explain the cause if the glycerol-phosphate shuttle is assumed to be prominent in brain cells. Several possible reasons might lead to this:- 1) The existing metabolic pathways are all intertwined to ...


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