29 votes
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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

Oxygen is actually not needed in the Krebs cycle - it is needed in the electron transport chain that is downstream of the Krebs cycle to regenerate NAD+ from NADH. NAD+ is a co-enzyme and acts as an ...
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Is lysergic acid diethylamide (LSD) metabolized in the body?

Short answer LSD appears to be enzymatically broken down in the liver. Background First off, hormones do not break down anything; enzymes are the work horses that mediate metabolism. According to a ...
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Is agriculture really a net contributor of greenhouse gases?

The issue is that it is not always a cycle, when you drain wetlands or burn forests to make more farmland that's not a cycle that is permanent change. A change that can continue having effects for ...
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19 votes
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Do birds emit infra-red radiation?

Short answer Birds emit infrared. Background Objects with a temperature higher than the background emit detectable infrared (IR). Endothermic (warmblooded) animals keep their body temperatures at ...
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13 votes
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Why does NAD+ become reduced if it gains a hydrogen proton?

You are correct that reduction is simply a gain of electrons. This results in a decrease in oxidation number. You know that NAD+ is reduced by this process because it starts off with a positive ...
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12 votes

Do any organisms recycle their own waste internally?

All organisms recycle their waste internally. Every cell of every living organisms is constantly breaking things down and re-using the components so produced. But you're presumably wondering about ...
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What is the purpose of gluconeogenesis?

Gluconeogenesis is not the reversal of the glycolysis, but the generation of glucose from non-carbohydrate precursors (like odd chain fatty acids and proteins). The reason why we have this process is ...
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11 votes
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Why do obese people tire quickly?

Fatigue on exercise is proportional to unmet demand for oxygen and glucose (sugar/fuel). In people who are "fat": They typically do less exercise. Therefore their cardiovascular system is not ...
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Are carbohydrates an essential component of human diet?

From a theoretical perspective this is a very interesting question, mostly because it is difficult to completely abstain from carbohydrate intake on a normal diet. Even the popular low carb diets of ...
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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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11 votes
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Origin of the biochemical term, Pi (inorganic phosphate)

This terminology is at least as old as September 1944 when Enzymatic Synthesis of Acetyl Phosphate Journal of Biological Chemistry 155, 55-70 was published by Lipmann, which says: Inorganic ...
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10 votes
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What is an irreversible reaction?

The term "irreversible" means that the reverse reaction occurs so rarely that it is considered negligible. This means that you do not have to consider equilibrium, as you have to for reversible ...
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Should we induce fever to assist healing?

Could it be beneficial to artificially induce fever in a person who has an illness if they are not already experiencing fever? No, not really. Pretty much the only use of hyperthermia in medicine is ...
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What is the brain's preferred energy source? Glucose or ketones?

First of all, for those readers with less knowledge of the general principles of biology, I want to state an important, even if obvious, point: The brain doesn't "prefer" anything. Despite ...
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Does Glycolysis produce lactate, or pyruvate?

I think you will find all text books (e.g. Berg et al. Ch 16) describe glycolysis as the conversion of glucose to pyruvate, as this is how it has been defined and considered in countless biochemical ...
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9 votes

Is lemon water an alkalizing agent in the body?

Short Answer: There was an interesting paper that dealt with the pH of urine when citric acid was consumed. The summary was: There was no increase in urinary pH or total nitrogen in 24 hours ...
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Why isn't the phosphoglycerate kinase reaction of the glycolysis pathway irreversible?

The free energy change that you quote for the phosphoglycerate kinase (PGK) forward reaction is, of course, the standard free energy change (ΔG0') for the overall reaction. The standard free ...
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What happens if a non-diabetic receives an injection of insulin?

Blood sugar drops (Hypoglycaemia) There are several other uses of insulin (other than diabetic treatment) Some of those could be: Diagnostics Psychology (Narcoanalysis) Parenteral nutrition ...
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Is palmitic acid really that dangerous?

Let's first clarify some concepts. Free fatty acids, including palmitic acid, are not present in animal tissues (or in the diet) to any large extent; they are esterified with glycerol to from ...
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Effect of cold showers after intense training

Taking cold showers(10-15 ℃) after training or workout have many benefits: It helps in lowering the damaged tissues temperature by constricting blood vessels. Cold helps numb nerve endings which ...
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How can grass-fed livestock generate fat?

Short answer Plants typically store energy in the form of starch. Animals, including livestock and humans for that matter, can digest starch, metabolize it into acetyl-CoA and turn it into fat. ...
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Why is carbon dioxide produced in alcohol fermentation but not in lactic acid fermentation?

Glycolysis needs a steady supply of NAD+ to happen - this is the driver for the anaerobic oxidation to lactate and ethanol, although this is energetically much less favorable than the complete ...
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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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How Does Green Tea Increase Metabolic Rate?

Interesting question! Green tea increases metabolic rate of body because it contains antioxidants known as catechins1. Catechins are actually polyphenol flavonoids, and have been shown by Wang et al ...
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Is there any use of CO₂ in human body?

To add my 2 cents worth: Breathing rate and depth is regulated by chemoreceptors in the medulla in the brainstem. These chemoreceptors primarily respond to pH of the blood, but the pH is for an ...
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8 votes

In Japan, the official average body temperature is 36.0 °C. Why so different from that of Europe?

Factors that can lower body temperature: low environment temperature low metabolic rate hypothyroidism I couldn't find any relevant study addressing the Japanese people situation, but: There is ...
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8 votes

Does THC excretion increase if urine volume increases?

This question asks about the urinary excretion of THC. Before answering the question I think you're getting at, I'll first note that cannabinoids (of which THC is one) are primarily metabolized by ...
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8 votes
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When glucose production is low, the brain begins using ketoacids as energy... how does that work?

Human body is a glucose driven machine which intake carbohydrates and converts to glucose. Energy is yielded from the glucose and glucose is stored as glycogen. When the carbohydrate intake is somehow ...
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8 votes

Is lysergic acid diethylamide (LSD) metabolized in the body?

LSD is metabolized in the liver in humans by enzymes of the Cytochrome P450 hemoprotein. The specific enzymes are CYP3A4 and CYP2D6. CYP2D6 is generally regarded as non-inducible (meaning there ...
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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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