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A reaction where the the free energy of a thermodynamically favorable transformation, such as the hydrolysis of ATP, and a thermodynamically unfavorable one, are mechanistically joined into a new reaction (or may be envisaged to be so joined) is known as a coupled reaction. To put it another way, two or more reactions may be combined mechanistically such ...


28

Before I restrict the answer to human metabolism, I recon it is important to mention that CO2 is the source of the carbon atoms of glucose in photosynthesis (in the Calvin cycle). [In photosynthesis CO2 is 'fixed']. Even with the above restriction, I am certain I cannnot do justice to every helpful aspect of CO2 in mammalian metabolism, and I'll restrict ...


26

Oxygen is actually not needed in the Krebs cycle - it is needed in the electron transport chain that is upstream of the Krebs cycle to regenerate NAD+ from NADH. NAD+ is a co-enzyme and acts as an electron carrier in oxidizing reactions at various positions in the Krebs cycle. However, note that without O2, NADH accumulates and the cycle cannot continue as ...


23

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 review paper (Passie et al., 2008), humans metabolize LSD into structurally similar metabolites (Fig. 1) by NADH-dependent microsomal liver enzymes to the ...


20

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 centuries. Then of course you have petroleum fuel used to run tractors and the production of fertilizer which are often not cycles either but pure extraction. ...


19

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 around 37oC and given the relatively cool temperatures at the earth's surface, endotherms generally emit more IR than the background. Endothermic animals include ...


18

Perhaps the question may also be phrased, "Why is it common for plants to produce chemicals that possess pharmacological or toxicological effects in man and animals?", and to that question it is often reasoned that plants, being sessile and otherwise defenceless food sources for predators, produce compounds that affect the physiology of animals in such a way ...


16

First of all, we should specify that there is no such thing as "HDL-cholesterols" and "LDL-cholesterols". On the same note there is no such thing as "good cholesterol" and "bad cholesterol": cholesterol is just one molecule, with this chemical structure What blood tests generally report is HDL-C and LDL-C, that is the amount of cholesterol in HDL or LDL ...


13

Some additional points about role of bicarbonate (which is directly formed from carbon dioxide as described by TomD): Helps is neutralizing the acidic chyme when it enters intestine. Formation of shells in invertebrates and eggshells in birds and reptiles. Shells are formed by deposition of calcite (calcium carbonate) which primarily happens by increased ...


13

The blood pH is tightly controlled since variations are quite dangerous for us. Under normal circumstances the pH is 7.4 (with a normal range between 7.35 and 7.45). Below that we are talking about acidosis, above it about alkalosis. If the blood pH goes about 7.8 or below 6.8, death will occur. This pH is maintained by the Bicarbonate-buffering system, for ...


13

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 charge (+1) and ends up with a neutral charge (0). The reducing agent that is donating the electrons is the hydrogen. More correctly, the electrons come from the ...


12

In the case of red blood cells: human erythrocytes (red blood cells) have no mitochondria. Since the mitochondria are the cellular site for oxidative metabolism of fatty acids, erythrocytes cannot oxidise fatty acids to release energy. The erythrocytes also cannot fully oxidise glucose (to carbon dioxide and water) because this is also a mitochondrial ...


12

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 things such as carbon dioxide, urine and faeces? These are not recycled because the benefits of doing so are not worth the costs. Let's consider carbon dioxide as ...


12

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 because some organs and tissues can only use glucose as their energy source. These include the brain (although ketone bodies can be used here as well), ...


11

There are some very general answers to your question. Definitely, there is a lot of magical thinking. We as humans are very prone to anecdotical evidence and extrapolations from incomplete data, even more so when we are drunk. As an interesting "proof" is the fact that the German counterpart of the saying "beer after wine and you'll feel fine,...


11

I thought this was a great question. In particular because it hints at two questions. The first is 'why carbohydrates are used to store energy' in general. The second being 'why glucose rather than other carbohydrates?' in particular. Glucose metabolism (and glycogen storage) is a core gene pathway - its found in bacteria archaea and eukaryotes. So ...


11

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 is found in smaller amounts in vegetables and fruit, as well. Adenosine can be found in many of the same foods, both as free ATP/ADP/AMP, and as part of the DNA ...


11

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 phosphate, referred to as Pi, was estimated colorimetrically See also the definition of "inorganic phosphate" and "orthophosphate" from this 1943 ...


10

The switch from glucose to ketone bodies as the principal blood metabolite accompanies starvation. This prioritizes the heart, which preferentially uses ketone bodies as a fuel (update; actually it's fatty acids, but they're metabolically similar.) This de-prioritizes the brain, which preferentially uses glucose. [edit] I was asked for a source. This is ...


10

First, the hormonal and hemodynamic changes seen in hangover are distinct from those seen in alcohol withdrawal, so the advice to drink more is not good, even if some symptoms are in fact improved. See tables 2/3 in the cited review. It appears the molecular mechanism of veisalgia (HA, a new word) is not well known. 1. acetaldehyde Part of it may be ...


10

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 reactions. Instead, you can assume that all of the reactants will eventually become product. As you stated, this is true for reactions that have a very negative ...


10

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 conditioned with the heart being able to cope with increased exercise i.e. it is unable to beat more efficiently and instead must beat A LOT more faster to cope ...


10

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 in the treatment of cancer. If you google "use of hyperthermia in medical treatment", you'll likely only find two kinds of hits: those for cancer treatment and ...


10

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 the late 1990s and early 2000s (e.g. Atkins Diet, South Beach Diet) were just that, they were Low Carb, Not No Carb. We know there are essential dietary ...


10

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 papers. The subsequent reactions of pyruvate are regarded as separate metabolic steps or pathways. The title of the short review article you cite (“Lactate is ...


9

Halsey & White (2012) Comparative energetics of mammalian locomotion: Humans are not different. Journal of Human Evolution 63:718–722 This paper presents a comparison of the metabolic cost of walking and running in humans, Australopithecus and other mammals. They use a parameter NCOT (net cost of transport), whose units are ml O2 consumed m-1. The ...


9

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 collection of urine. What This Means: The food we take does not affect the blood pH directly. Acidic food will cause increased secretion of alkaline components into ...


9

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 energy change is defined for all reactants at a concentration of 1M. Note that this value includes the formation of ATP - the free energy of hydrolysis of 1,3-BPG ...


9

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 hepatic cytochromes rather than being excreted directly. This article is a classical pharmacokinetic paper on the topic if you’re able to access it; this one is a ...


9

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 Cardiology (Glucose–insulin–potassium solution (GIP or GIK solution) is given after a myocardial infarction) Malignancy (Insulin potentiation therapy (IPT)) ...


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