The set of biochemical reactions that sustain life by directly or indirectly affecting energy expenditure and/or storage, as well as the complete regulation of those reactions and the enzymes that catalyze them; including, hormonal, cell-signaling, and substrate level regulation.

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Would short term increases in oxygen lead to beneficial effects?

After some thinking, I am wondering if having a 30% atmospheric oxygen concentration (or some other concentration) for a short time would increase the regeneration of energy in a body? It seems like ...
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30 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 six hydrogens and becomes ...
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16 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 ...
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18 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 ...
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2answers
45 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 ...
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1answer
58 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 ...
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1answer
47 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?
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4answers
72k views

What is a coupled reaction and why do cells couple reactions?

I was wondering what exactly a coupled reaction is and why cells couple them. I read the wikipedia article as well as several others, such as life.illinois.edu but I still don't get it. Could ...
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1answer
32 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. ...
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2answers
47 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?
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60 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 ...
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2answers
612 views

Where can I find a list of common enzyme cofactors and/or co-enzymes?

Where can I find a list of enzyme cofactors and/or co-enzymes, ordered by how common they are? For example, $O_2$, $H_2O$, $ATP$, $ADP$, $NAD$, should be ranked in the first places, because they ...
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1answer
31 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 ...
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1answer
64 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?
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2answers
36 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 ...
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3answers
110 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 ...
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1answer
44 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 ...
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0answers
31 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 ...
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1answer
33 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 ...
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26 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 ...
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3answers
1k views

What are the differences between how glucagon and cortisol work to increase blood sugar?

As I understand, both cortisol and glucagon cause an increase in blood sugar concentrations. However I don't understand how they work differently or why they work separately. I would be very grateful ...
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1answer
25 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"?
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1answer
149 views

Are carbohydrates an essential component of human diet?

Are people able to satisfy all the needs of a healthy diet without consuming carbohydrates? My question includes the assumption that a person has no health condition that would prevent them from ...
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0answers
23 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 it and a hyperauxotroph lacks both the biosynthetic pathway and the transporters. ...
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24 views

Insulin and leptin action on Anorexigenic Neurons in Hypothalamus?

Receptors for Insulin are present on liver, adipose tissue and muscles BUT also Insulin Receptors are present in arcuate nucleus of hypothalamus where it influences anorexogenic neurons through IRS2 ...
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1answer
38 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 ...
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1answer
21k views

Why is my faeces black in color after eating Oreos

Why is my faeces black in colour the morning after I eat some Oreos? Day 1 : Eat a handful of Oreos & the next morning your stool is black. Day 3 : Eat a handful of cocoa flavored biscuits & ...
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38 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 ...
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3answers
552 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 ...
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4answers
3k views

Is lemon water an alkalizing agent in the body?

I was recently having a discussion with someone about whether lemon water actually increases the pH of your body (by which I assume they mean the blood); their claim was that once Citric acid was ...
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1answer
55 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?
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1answer
6k views

What is/are the molecular differences between HDL and LDL cholesterol?

Why exactly is HDL-cholesterol good for us and LDL-cholesterol bad for us. It has been well-established that LDL-cholesterol is associated with atherosclerosis and that HDL-cholesterol helps remove ...
5
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1answer
70 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 ...
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16 views

How to Stabilize Histamine Surges in Exercise of MD/DMII?

I am studying how to stabilize histamine surges/effects without antihistamines in exercise of Metabolic Syndrome (MD) and Diabetes Mellitus II (DMII). Generic/simplified case: Symptoms in exercise: ...
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1answer
239 views

Where do the H+ ions come from in light reactions?

In the light-dependent reactions of photosynthesis, H+ ions pass to the thylakoid space. Where do these protons come from?
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1answer
2k views

What does vitamin B6 and B12 absorption depend upon?

I'm looking at my question about homocysteine metabolism and am doing a followup inquiry into vitamins B6(Pyroxidine) and B12(Cyanocobalamin). I've found this interesting bit about vitamin B12 and am ...
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1answer
36 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 ...
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1answer
106 views

Statistical method for characterizing the relationship between body mass and metabolic rate

There is a dataset that contains body mass ($x$) and metabolic rate ($y$) from many different organisms. It is common to fit the data to the model of the form $y=ax^b$ and estimate the parameters $a$ ...
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14 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 ...
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1answer
48 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 ...
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1answer
57 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 ...
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27 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? ...
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0answers
21 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 ...
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19 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, ...
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0answers
19 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 ...
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0answers
27 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 ...
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1answer
119 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.
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10 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 ...
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400 views

In a tumor, why hypoxic regions have access to glucose?

The Warburg effect is ubiquitous in cancer. It consists of the upregulation of glucose uptake, glycolysis, and subsequent lactate secretion, sometimes by over 200 times, in cancer cells as compared to ...
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16 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? ...