45 votes
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Does 1kg of lettuce have more energy than 1kg of beef?

1kg of beef has more energy than 1kg of lettuce but it isn't directly related to the trophic level energy loss. Given that each level of the food chain has a decrease of 10% of available energy You'...
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38 votes

Does 1kg of lettuce have more energy than 1kg of beef?

The so-called '10% law' is a common, albeit very rudimentary, rule-of-thumb in foodweb analysis. It's commonly attributed to Raymond Lindeman, though he cited a wide range of ratios in natural systems....
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35 votes
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What is the human energy consumption by organ?

Percent of basal metabolic rate by organ (BC Campus Open Education): Liver and spleen : 27% Brain: 19% Skeletal muscle: 18% Kidneys: 10% Heart: 7% Other tissues (lungs, intestine, skin, bone, fat ...
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11 votes

What is the ultimate source of ADP/ATP in humans?

Phosphorus is a very common nutrient, found in high levels in proteins, which are in such foods as milk and milk products, meat, beans, lentils, nuts, and grains, especially whole grains. Phosphorus ...
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9 votes
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How much energy does a small spider expend per day just waiting for its web to vibrate?

Short answer Approximately 240 J on a daily basis. Background Ballesteros et al. (2018) modeled basal metabolic rates of insects. They reckoned that endotherms, like insects, basically use energy ...
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8 votes

Does food lose some of its mass in form of energy during metabolism?

Physics answer that is a bit silly If you want to be real technical about physics, mass and energy are the same thing, so any chemical bond that has some energy and is broken results in a change of ...
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8 votes

Does 1kg of lettuce have more energy than 1kg of beef?

The (food) energy in 1kg of lettuce or 1kg of beef depends on each's composition, not on its trophic level. Normally we can digest fats, protein and carbohydrates, but other organisms like certain ...
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  • 1,689
7 votes

Why is oxygen needed for the electron transfer phosphorylation?

Aren't there any other alternatives for this acceptor? Yes, there are multiple other acceptors used by anaerobic bacteria. Iron is probably the most common other acceptor used by a range of organisms ...
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7 votes
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Why is oxygen needed for the electron transfer phosphorylation?

Aren't there any other alternatives for this acceptor? Not that we're aware of. Every other alternative requires an anaerobic environment - which means small, and often less efficient. Oxygen is ...
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7 votes
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How does the human body extract energy from ethanol?

Preamble The question suggests unfamiliarity with the nature of biochemical oxidations and their relation to energy transfer in biology. The naïve reader is recommended to consult a text for a ...
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7 votes

Understanding entropy and the second law of thermodynamics as involved in metabolic processes

2nd law of thermodynamics states that the overall entropy of the universe cannot decrease at any time. This can also be stated as the fact that the universe naturally falls towards the lowest energy ...
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6 votes

Reason for conversion of glucose to fructose in glycolysis

Avoiding diffusion is one reason to phosphorylate glucose, the other is that it is removed from the osmotic balance between inside and outside of the membrane, so it can be transported at a high rate. ...
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6 votes

How do plants store energy by potassium battery?

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 ...
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6 votes
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Breathing faster to lose (more) weight?

The rate of CO2 production is normally set by the rate of metabolism and breathing rate is determined by the level of CO2 in the blood. What you are suggesting is known as hyperventilation. Because ...
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6 votes
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Quinone A, Quinone B, Ubiquinone, Plastoquinone: whats the difference?

Difference between Ubiquinone (UQ) and Plastoquinone (PQ) Structural Difference: Structurally, UQ and PQ are very similar. They only differ in a methyl group and 2 substituents on the benzoquinone ...
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6 votes
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Why is ATP hydrolysis to ADP, rather than ADP hydrolysis to AMP, used to drive biochemical reactions?

Summary The original question was edited — with the approval of the poster — so that in brief it now asks: Why is ATP hydrolysis to ADP, rather than ADP hydrolysis to AMP, the normal way in ...
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6 votes

About the definition of ketogenic amino acid

The fundamental 'problem' with acetyl-CoA is that it cannot be converted to glucose via the tricarboxylic acid (TCA) cycle: a two-carbon compound (acetyl-CoA) enters the TCA cycle, but two carbons are ...
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6 votes

What determines whether a reaction using ATP produces ADP or AMP?

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 ...
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6 votes
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Pyruvate dehydrogenase: Apparently anomalous NAD/FAD redox reaction

Summary The redox potential widely quoted in text books for the half-reaction reduction of FAD to FADH2 is indeed inconsistent with the observed direction of several reactions involving this coenzyme, ...
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5 votes

Anabolic reactions and reaction energy

Both statements are correct, but an understanding of why they are not contradictory requires a bit of explanation. For "spontaneous" reactions, those which occur naturally, entropy must always ...
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5 votes
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Cellular Respiration/Fermentation Problem Leading to Lack of Energy

Short answer (A) is a possible answer and is indeed cause for fatigue, as pyruvate is needed for the Krebs cycle to run. The krebs cycle is an essential step in the generation of ATP in aerobic ...
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5 votes

Do all prokaryotes have ATP synthases and an electron transport chain?

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 ...
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5 votes

Why is ATP hydrolysis to ADP, rather than ADP hydrolysis to AMP, used to drive biochemical reactions?

It can, and a very famous example is polynucleotide phosphorylase, an enzyme of great historical importance in the elucidation of the genetic code. That said, it is very uncommon, and ...
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5 votes
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What are the bare minimum nutrients required to survive as a human?

Essential nutrients include (NutrientsReview): Water 9 amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, tryptophan, threonine, valine 2 fatty acids (alpha linolenic and ...
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  • 7,969
5 votes
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Apparent paradox in Glucagon action

Summary The apparent paradox is resolved by the fact that not all tissues possess receptors that cause them to respond to glucagon or, more generally, to the same hormone. Where different tissues do ...
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4 votes
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How many protons are pumped out per pair of electrons from NADH in oxidative phosphorylation?

It seems like the mistake is in complex III. Look at this image from here: It clearly shows the number of protons reduced in (and taken from) matrix and number of protons pumped into inter-membrane ...
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4 votes

What is the fate of NADH produced in the liver during oxidation of lactic acid?

The “best guess” in this question is incorrect and the question itself indicates a lack of understanding of the roles of NAD+ and NADH in energy metabolism. (To rectifiy this, Chapters 17 and 18 of ...
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4 votes

How did giant sauropods satisfy their daily energy needs, considering their relatively small mouths?

Unlike mammals, saurischian dinosaurs don't have to chew their food. Like birds they have a gizzard to do that instead. Look at a modern ostriches: they have a very small head because the head is ...
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4 votes
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Does the energy from ATP hydrolysis vary among different cells?

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 ...
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  • 5,595
4 votes
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Which complexes physically pump protons in photosynthesis?

General Approach Although I am not an expert in this area, as an ex-chemist I find this topic one of the most fascinating and fundamental in chemical biology. I have constructed an answer starting ...
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