Questions tagged [metabolism]
Metabolism is the set of defined biochemical transformations occurring within the cells of living organisms.
478
questions
5
votes
2answers
1k views
What is the source of the electrons generated in the Krebs cycle?
In the Krebs cycle, where do the hydrogens and electrons that NAD+ and FAD accept come from? It seems that citric acid only loses two hydrogens because it starts out with eight hydrogens and then ...
0
votes
0answers
154 views
What would the presence of a hub metabolite in a metabolic pathway signify?
Say I have a metabolic pathway, consisting of multiple metabolites and reactions. On analyzing the pathway I find that among all the metabolite, one metabolite is the hub metabolite (hub metabolite is ...
0
votes
0answers
45 views
Co-dependency between carbohydrates, fats and protein in the mammalian diet?
Following up from the question Are carbohydrates an essential component of human diet? I am interested in knowing more specifically how carbohydrates, fats and proteins are linked in the mammalian ...
0
votes
2answers
76 views
How did scientists establish the reactions that occur in metabolism? [closed]
How did scientists establish that macromolecules like proteins, carbohydrates and lipids are synthesized from other molecules with intermediate products by living cells. Did they observe this under ...
2
votes
1answer
94 views
Is there a certain environment where all cellular functions (or at least some) increase their rate?
Is there a certain environment in which all the functions (or some) inside a cell increase in their rate? Would the increased rate cause any damage to the cell?
1
vote
1answer
1k views
Are there known functions of AST, ALT, and amylase in the blood?
A number of enzymes can be measured in the blood or plasma that aid in the diagnosis of certain diseases. For example, patients with particular liver diseases may have elevated aspartate ...
5
votes
1answer
5k views
Why is the Pentose Phosphate Pathway so active in erythrocytes?
Is it because glyceraldehyde -3-phosphate (a molecule which when enter glycolysis help produce ATP through substrate level phosphorylation) can be prepared without losing an ATP through this process?
4
votes
4answers
6k views
What is the actual storage form of energy in muscles? ATP or Glycogen?
I was asked this question in my latest exam. I think the answer is Glycogen because ATP doesn't store energy for a long time so it isn't the ACTUAL storage of energy. Some classmates argue that in ...
0
votes
2answers
1k views
Energy coupling between two spontaneous reactions?
This diagram describes energy coupling between a nonspontaneous reaction (the formation of glutamine from glutamic acid and ammonia) and a spontaneous reaction (the hydrolysis of ATP). I can see that ...
1
vote
2answers
13k views
Where do transamination and deamination take place?
The only information I know is about deamination is that it occurs in the liver and kidney. But in which part of the cell does deamination occur? To which tissues is transamination specific, and in ...
1
vote
0answers
516 views
Can the respiratory quotient be calculated from a formula or must it be measured directly?
I found the following question on the Respiratory quotient:
A normal human diet has a Respiratory quotient (RQ) of approximately 0.85. Given that pure oxidation of fatty acids has a Respiratory ...
2
votes
0answers
50 views
Validity of measurements of respiration in isolated mitochondria
I've recently read a couple of papers on exercise and mitochondria, in which state 4 and state 3 respiration rates and ROS production are assessed in vitro after exercise has been performed (i.e., rat ...
0
votes
1answer
45 views
Do I have to chew for digestion to kick in?
Liquid nutrient-rich products (such as Soylent) are consumed without chewing. But if I have to chew to initiate digestion, are those nutrients really "processed"?
4
votes
2answers
195 views
Where do plants obtain the metal ions needed for biological processes?
Enzymes employ metal ions (e.g. Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn) for catalysing certain reactions.
Let's consider planting a seed. Where will it obtain these metal ions from? Just from water?
3
votes
1answer
120 views
Term of the type xxx-troph for a compound not used by an organism
A prototroph for compound X can make it
A bradytroph grows faster if X is scavenged
An auxotroph needs to scavenge X
A hyperauxotroph lacks both the biosynthetic pathway and the transporters for X
...
1
vote
0answers
134 views
Insulin and leptin action on Anorexigenic Neurons in Hypothalamus?
Receptors for Insulin are present on liver, adipose tissue and muscles. In addition, there are Insulin Receptors present in arcuate nucleus of hypothalamus, which influences anorexogenic neurons ...
1
vote
1answer
395 views
Why are both glucagon and cortisol released in hypoglycemia?
Cortisol is released in response to prolonged stresses; one situation when cortisol is released is when blood glucose level is low. In this situation cortisol acts on adipose tissue promoting fatty ...
1
vote
1answer
2k views
Fate of Acetyl CoA in well fed state?
When we have eaten well and take fat rich diet then in this condition Acetyl CoA produced from fatty acid breakdown will be gone to storage in adipose tissue or not? If it will go for storage then why ...
3
votes
1answer
821 views
What is the substrate for glycogenesis?
In glycogenesis (i.e. the synthesis of glycogen), are sugar phosphates the direct substrates for glycogen polymerization? I would certainly think so since glucose is phosphorylated and then stuck onto ...
2
votes
1answer
577 views
Thyroid hormone metabolism and excretion
My understanding is that hormones generated by the thyroid gland, including, for example, T4, are excreted and recirculated in the body through the digestive tract. The reason for thinking this is ...
0
votes
1answer
408 views
Why does cold kill humans but not bacteria? [closed]
Bacteria can continue like nothing happened after being exposed to low temperatures why doesn't this happen to humans as well? Why can't our metabolic machinery continue as normal?
2
votes
1answer
1k views
What's the highest glucose concentration (in mM) anywhere in the human body (tissue, capillaries, tumor microenvironment, etc.)?
Glucose blood levels are around 5mM, or 10mM after meals. In capillaries these levels can rise by about 40 %. I haven't found measurements of glucose concentration in tissues, or in extracellular ...
1
vote
0answers
21 views
Could there be some safe, hypothetical way of turning on and of thermoregulation?
This is something I thought of with the whole artificial gill concept. Could a modification to the brain/nervous system allow a human to turn off their thermoregulation in air/water of the right ...
4
votes
1answer
2k views
Can lactate be created in ketosis?
After looking at Cori Cycle (from wikipedia)
I have a question about how the lactate can be produced in ketosis. According to this article:
in a low-glucose state, where the body senses that ...
2
votes
1answer
102 views
Does the body prioritise the use of available sugar before fat?
Let's say you eat a very unhealthy snack that contains 90% sugar and 10% fat. Would somatic cells not start using the fat for energy until all the sugar is used up?
Does the body not use fat at all ...
1
vote
1answer
122 views
Bilirubin metabolism and UGT1A1 inhibition in human vs. monkey?
In human UGT1A1 seems to be the only relevant enzyme to glucuronidate unconjugated bilirubin into excreted forms. Is the pathway the same for e.g. the Cynomolgus monkey (Macaca fascicularis) in vivo? ...
5
votes
1answer
182 views
How can I obtain a computer readable model of Dr. Gerhard Michal's biological pathways map?
I want to run simulations of various metabolic pathways – the project could end up becoming quite large, and having a machine readable chart would make thing a lot easier. Does anyone know if there is ...
3
votes
4answers
4k views
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 ...
5
votes
1answer
129 views
Cellular demand for antioxidants
Antioxidants such as ascorbate and glutathione serve to inactivate radicals and counteract spontaneous oxidation reactions, such as unwanted disulfide bonds in proteins. These systems are cycles, ...
1
vote
0answers
41 views
Anaerobic nutrient expenditure
Doing some research into different forms of exercise and energy systems and I realized something odd about the way we talk about energy.
When we eat, we take on macronutrients that are broken down ...
5
votes
1answer
141 views
How are ions 'pumped' across a membrane during electron transport?
A number of sites (including this one) that provide descriptions of photosynthesis state that high energy electrons 'pump' ions across a membrane. What is the actual 'pumping' mechanism? I've looked ...
1
vote
0answers
41 views
Need to solve a “pseudo-metabolic” network for rates
following problem:
I have data on a certain complex association network (from monomers 1 ... 8 to complexes of all combinations, such as, 12 ... 13 ... 18 and so on until 12345678, so that I know
...
3
votes
0answers
111 views
Are there animals that can deliberately manipulate their metabolism, apart from hibernation?
Are there animals that can slow down their metabolism deliberately? I know that hibernation would be one mechanism, and maybe being cold-blooded, but I was wondering if there was maybe an animal that ...
-2
votes
1answer
1k views
What is ATP and why is it said to be a source of energy? [closed]
Is ATP a molecule or a kind of energy. When I studied the active transport, it's said the ATP would release energy to change the carrier protein shape. So confused.
Thanks for your help.
1
vote
0answers
97 views
Is it possible to stimulate the EPOC process?
On Wikipedia, EPOC is defined as:
Excess post-exercise oxygen consumption (EPOC, informally called afterburn) is a measurably increased rate of oxygen intake following strenuous activity intended ...
1
vote
0answers
24 views
Bilirubin metabolism pathway in non-human primates (NHP)?
In human UGT1A1 seems to be the only relevant enzyme to glucuronidate unconjugated bilirubin into excreted forms. Is the pathway the same for e.g. the Cynomolgus monkey (Macaca fascicularis) in vivo? ...
4
votes
1answer
138 views
Why does our body regulate metabolic processes using the thyroid hormone?
People with hypothyroidism do fine when taking medication containing their daily dose of thyroid hormone. This means that the signaling function of the thyroid hormones is, in principle, unnecessary. ...
2
votes
1answer
738 views
What are calories and how to burn them? [closed]
What exactly is a calorie? When burning calories, do we always lose fat?
I have tried many apps to measure calories, do they give exact amounts? How many calories should be taken a day?
1
vote
0answers
558 views
If chylomicrons can not get into the capillaries, how do they supply to tissues?
The transport of chylomicrons is into the lacteals mainly because they are too big to get into the capillaries and yet they later supply triglycerides in the extra hepatic tissue by traversing in the ...
2
votes
1answer
89 views
Why does protein kinase C activated by different means have different effects?
I could be way off base but I think I remember learning that Protein Kinase C has some effects when activated by one pathway and other effects when activated by another. How does this happen? Is it ...
2
votes
1answer
434 views
How many calories do gut bacteria burn?
It has become well-accepted that microbiota of the gut (a.k.a. gut bacteria) consume calories that are ingested and can have significant effects on energy metabolism in humans. For example, if you ...
3
votes
2answers
2k views
Can bacteria metabolize fatty acids for fuel?
I'm not a microbiologist, but rather a physiologist curious about microbial metabolism. Much like humans bacteria can utilize glucose, but when it comes to long chain, medium chain, or short chain ...
4
votes
2answers
457 views
Are there bacteria that respire anaerobically in aerobic conditions?
There are facultative anaerobic bacteria that switch to anaerobic respiration in an anaerobic state, but are there any organisms that would still perform anaerobic respiration even when shifted to ...
3
votes
0answers
203 views
What is the function of CETP?
I read up that CETP transfers cholesterol from HDL, which collected it from tissues, to VLDL. This VLDL is then sent back to the tissues, ultimately forming LDL internalised by cells.
What is the ...
3
votes
0answers
64 views
What is the rationale behind reverse cholesterol transport?
Reverse cholesterol transport is transport of cholesterol from the tissues back to liver/VLDL. My question is why do the tissues have this extra cholesterol in the first place?
Why would you ...
4
votes
1answer
579 views
How can space-time affect ageing? [closed]
I recently watched the movie -"interstellar" and I came through the question that how can ageing be affected by space-time? Wherever I look, I get it as a fact that it's kind of ageing slows down in ...
2
votes
1answer
424 views
Are alpha-ketoglutarate and glutamate involved in all transamination reactions?
Is it true that for all biochemical transamination reactions, that alpha-ketoglutarate and glutamate serve as the amino group acceptor and donor, respectively?
If this is true, then is it safe to ...
2
votes
0answers
82 views
Why lactate inhibits growth (or enhances death rate)?
Extracellular lactate tends to inhibit cellular growth or enhance cell death. This happens in the vicinity of tumors and in cell cultures.
See for example this reference: Ozturk, Sadettin S., Mark R....
1
vote
0answers
26 views
Glycoprotein hormones metabolism
Why do the carbohydrate groups in glycoprotein hormones decrease the rate of metabolism? And increase the half-life?
10
votes
3answers
25k views
What happens if a non-diabetic receives an injection of insulin?
If a person without diabetes or any diabetes-related issues receives an injection of insulin, what happens? Would the blood glucose level drop or does the body naturally compensate for the added ...
