Questions tagged [metabolism]

Metabolism is the set of defined biochemical transformations occuring within the cells of living organisms.

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Why does pyruvate from lactate and pyruvate from other sources follow different pathways in gluconeogenesis?

My teacher taught me in a lecture that PEP forms from Pyruvate by two ways, based on their sources, that is - 1. If the Pyruvate was from lactate (by lactate dehydrogenase action), it gets shuttled ...
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Is gut bacteria Succinivibrionaceae's low methanogenesis understood well enough for GM of cattle gut bacteria to be considered?

After watching the Periodic Table of Videos episode linked in this question I watched the episode Wallabies and Methane where Sir Poliakoff says (a bit after 02:00):...
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Why is some scat in the form of little pellets?

The scat I most often encounter when out and about is from coyotes, black bears, deers and rodents. The deer and rodent droppings I find are in little pellets, what is different about their digestive ...
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How are Mono and Diglycerides metabolized without the Free Fatty Acids of Triglycerides?

Having difficulty figuring out what the body does with ingested mono and diglycerides if the usual process of TAG metabolism includes the FFA released from the TAG returning to the MAG to recreate a ...
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During starvation, does the human body do anything to prioritize which organs receive nutrients?

When food is scarce, the body slows its metabolic rate to conserve energy. Are there any other systems or processes that prioritize which organs receive nutrients?
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Is anaerobic activity during ketosis possible?

When a person's glucose and glycogen stores are depleted, which can occur due to fasting or due to a diet consisting largely of fat (like eskimo diets), the body produces its energy by breaking down ...
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Complete metabolic map of humans [closed]

Do we have the complete metabolic map for humans? Do we know from the genome what enzimes are expressed and what each enzime does?
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Breeding mosquitoes at lower temperature

It is well known fact that, to slow down the growth of drosophila, they are grown at 18-19 degree Celsius. It helps in maintaining stocks for longer time without frequent change of food. Is it ...
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Where do the four ADPs come from in the second stage of glycolysis?

In the first stage of glycolysis, the two molecules of ATP are broken down into 2 ADPs + 2 Pi through hydrolysis, then in the second stage of glycolysis they are phosphorilazed to obtain 2 ATPs. How ...
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How cells determine how many enzymes are needed for digestion

How do pancreatic cells, epithelial cells of the stomach and intestinal epithelium cells determine the right amount of enzymes for digesting carbohydrates, proteins, fats? How does the pancreas ...
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Why is Cacao a stimulant?

As I write this I've just eaten a fair amount of cacao (not cocoa) powder and it's given me quite a buzz. I've googled the effects and the Internet seems to think it's somehow psychoactive although it'...
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How does a glucose molecule enter the cell from blood vessel?

The transporters in the plasma membrane of the cells promote the entry of glucose molecules from the extracellular matrix to the cytosol of the cell. Could someone explain how does the nutrient ...
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Anaerobic respiration choice in E. coli

Under anaerobic conditions E. coli has two options to generate ATP: fermentation (substrate-level phosphorylation), and respiration (proton gradient, chemisomotic phosphorylation). Which is favored? ...
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Can the face bones be “compressed” or forced together? What would happen? [closed]

Say someone doesn't like that their maxilla bone is too long because the height of the maxilla affects the placement, position and angle of the mandible relatively. If one were to apply mechanical ...
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At what total rate is water used in metabolic processes over the entire biosphere?

A recent column on "The Straight Dope" website discussed the idea that water molecules are largely cycled around through the water cycle, and that therefore the water molecules that come out of your ...
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What waste products do cells secrete in culture, and at what rate?

I am designing microfluidic chips for mammalian cell culture. One aspect I am interested in modeling is the rate at which I must renew media to ensure that: Cells receive enough nutrients Cytotoxic ...
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Should heart-to-body energy consumption ratio equal oxygen consumption ratio?

The human heart pumps oxygen to the body, and the heart itself requires oxygen. Both the body and the heart use energy, usually expressed in calories or ergs. If we look at the energy consumption (...
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Can something like McDonalds be considered a life form?

"The current definition is that organisms are open systems that maintain homeostasis, are composed of cells, have a life cycle, undergo metabolism, can grow, adapt to their environment, respond to ...
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If life began at sea, why organisms are less salty than the sea?

We may take it for granted that a fish, a seaweed, or clams are not too salty to eat, although the sea around them is salty. I know about the existence of a mechanism which prevents their body from ...
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Does Povidone-Iodine that penetrates through the skin stays in the body (cells, liver etc)?

Here it says on povidone-iodine: "Route of Elimination: Povidone-Iodine is intended for topical application and is not eliminated" "Clearance: Povidone-Iodine is intended for topical ...
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Specific Neurons that Require Glucose

I've been doing a bit of armchair biology lately, and have been interested in the metabolic flexibility of neurons. My understanding is that, besides glucose, many neurons can metabolize lactic acid ...
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Cause of Obesity

Considering the normal function of adipose tissue in sequestering 'persistent organic pollutants [POPs]', is there any evidence that the existence of such POPs within fat cells interferes with the ...
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Why is hydrogen sulphide being generated on Caribbean beaches?

Once again, there has been a massive influx of Sargassum weed in the Caribbean. It is coming ashore on Atlantic facing beaches and forming piles up to 3m deep. As it dries and decays, hydrogen ...
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Can E. coli make pyruvate from acetate?

What pathway would E. coli use to make pyruvate from acetate? I have found several papers that refer to a possible mechanism that could move acetate to pyruvate via a three-step process: Step 1: ...
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How is the urea cycle regulated with respect to protein deficit?

Proteins cannot be stored in the body. Excess proteins from the diet are deaminated in the urea cycle that takes place in the liver. The liver is the first contact since these amino acids are ...
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In ketogenesis, why is acetacetyl-CoA not directly hydrolized to acetoacetate in ketogenesis?

Ketogenesis pathway maps show acetoacetyl-CoA converted to HMG-CoA and only then to the first ketone body acetoacetate. Why this detour instead of directly hydrolyzing off the CoA to get there in a ...
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When you lose weight, how does the mass exit your body?

As a thought experiment, consider the case of Angus Barbiery, who allegedly lost almost 200kg in about a year by not eating at all, save for necessary nutrients provided as supplements. My question ...
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Why does GLUT2 (With a high Km), bind less glucose at a lower glucose concentration (below Km)?

A text I am reading says "GLUT2 is a low-affinity transporter in hepatocytes and pancreatic cells. After a meal, blood travels through the hepatic portal vein and GLUT 2 captures excess glucose for ...
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Dangers of excess blood protein? [closed]

Like glucose, amino acids are also insulinogenic as well. So, presumably, just like glucose, the body would also like to keep amino acids levels in the blood stream below (or within) some certain ...
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1answer
27k views

Why does NAD+ become reduced if it gains a hydrogen proton?

I've heard that $\ce{NAD^+}$ gains a Hydrogen proton during glycolysis and the Krebs cycle and becomes reduced to $\ce{NADH}$. However, isn't reduction when a molecule receives an electron? Maybe I'...
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Are some polyketides enzymes?

I am currently reading a "book" (rather an article) called "Protein Modelling & Molecular Docking: Modeller, Autodock". The abstract starts with the following sentence : Polyketides are a ...
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Why are there so few multicellular anaerobes?

There are a few documented cases of multicellular anaerobic organisms, but I can't see a reason for it to not be more common. On the contrary, it seems pretty useful to be able to create energy even ...
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Was lactose present in the environment before the evolution of mammals?

Are there lactose sources other than dairy products in nature? I tried to search for it but I did not find anything. The question arose because I was wondering whether lactose-utilising enzymes in ...
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Bacteria utilize short chain fatty acid as energy source

I'm doing research about the short chain fatty acid producing bacteria. I studied 7 short chain fatty acid (acetic propionic butyric isobutyric valeric isovaleric and captionic). and I found that the ...
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What happens to lipoprotein lipase after a sugar only diet?

Insulin increases the activity of lipoprotein lipase thay allows cells to take in lipids from chylomicrons in the blood. If a person takes a sugar only meal like drinking coke, insulin is released. ...
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ATP Hydrolysis to AMP in the Urea Cycle. What is the Free Energy Change?

How is the hydrolysis of ATP into AMP and PPi in making arginosuccinate equivalent to the hydrolysis of 2 ATP?
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Does thyroxine increase BMR or metabolic rate?

I know that thyroxine increases the metabolic rate, but my teacher said it increases the metabolic rate, not the basal metabolic rate, the basal metabolic rate is always the same. What's the ...
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Why are my calculations for O2 requirements of daily metabolism so far off?

When I attempt to calculate the O2 necessary for a day of metabolism at rest (for an imaginary average human) and compare it with the expected O2 consumed per day my results differ by a factor of 3. I ...
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1answer
274 views

Negative Oxygen Consumption Rate

Oxygen consumption rate (OCR) is defined as the rate at which cells consume oxygen. I reason that for cells not capable of photosynthesis, OCR is strictly non-negative. That was until I read this ...
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187 views

Why can't humans use dietary citric or acetic acid as a primary source of energy?

As the Krebs cycle is involved with the conversion of food in to citric acid, why can't eating citric acid be used as a temporary primary source of energy - in place of fat/carbohydrate/protein?? It ...
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why is LPL (lipoprotein-lipase) down-regulated during fasting?

During fasting our body needs additional sources of energy and that's why triglycerides are broken down into fatty acids and glycerol. where fatty acids can be used to generate acetyl-coA and ...
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Is there any evidence that supports glycolysis in mitochondria or chloroplasts?

Glycolysis is known to be a part of cellular metabolism undergone by both eukaryotic and prokaryotic cells, whether under aerobic or anaerobic conditions. As the endosymbiotic theory states that ...
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Can animals make their own unsaturated fatty acids?

I know that animals can't make poly-unsaturated fatty acids (PUFA) and so require them from dietary sources. For eg.Omega -3 and Omega 6 fatty acids. My questions : Can animals synthesize other ...
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Is there a point in our life when ALL the atoms from our childhood's body get replaced?

The evolutionary biologist and Oxford professor Richard Dawkins makes on his TED talk the rather interesting suggestion that we human beings, are in nature more similar to a wave than an object. In ...
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Simplest known form of aerobic glycolysis

What is the simplest known way that an organism performs aerobic glycolysis? In other words, what is the simplest known way known to convert glucose into $\ce{H2O}$ and $\ce{CO2}$, other than by ...
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Why is glucose our primary source of energy?

Is there any evolutionary reason for glucose being the "main" molecule used as a source of energy, beginning with glycolysis and subsequently cellular respiration (after being converted to two ...
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How didn't large, highly active dinosaurs overheat?

The cube-square law seems to be the deciding factor when it comes to biological heat management. Small organisms with large surface areas relative to their volumes, like mice, need fast heartbeats and ...
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99 views

Does minimizing hunger maximize weight gain?

Due to the "obesity epidemic," there is a lot of focus on the causes of weight gain. We typically talk about strategies to cause weight loss, but what about strategies to minimize/maximize hunger? ...
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Extra-mitochondrial conversion of Acyl Carnitine to Acyl CoA

Normally fatty acids in the form of acyl CoA are converted to acyl carnitine in a reaction catalysed by carnitine palmitoyltransferase I (CPT1), which is also known as carnitine acyltransferase I. ...
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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 ...