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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11
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3answers
430 views

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?
10
votes
3answers
1k views

What is the purpose of gluconeogenesis?

The gluconeogenesis pathway seems quite pointless to me. I don't understand why an organism would want to spend energy to create a molecule that can then be metabolized again for less energy? The ...
2
votes
1answer
58 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?
2
votes
1answer
50 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 ...
1
vote
0answers
27 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
46 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 ...
1
vote
1answer
31 views

How is the enzyme glycogen synthase regulated?

How is the enzyme glycogen synthase regulated in regards to glycogen synthesis? I think I understand that phosphorylation decreases its activity (through glycogen synthase kinase?), but what role do ...
3
votes
2answers
81 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 ...
3
votes
2answers
150 views

How do muscle cells synthesize glycogen?

Hexokinase enzyme is present in all cells (including muscle cells) and can be suppressed by excessive G-6-P product. So that's why in the liver, glucokinase can act on glucose without inhibition of it ...
8
votes
2answers
75 views

Is there a metabolic pathway that generates methanol?

I've been looking for help topics about methanol in metabolism. Specifically, I wish to know what is a common dietary component that generates methanol following metabolism and comment on its toxicity?...
3
votes
0answers
29 views

Are there bacteria that respire anaerobically in aerobic conditions?

There are facultative aerobic bacteria that switch to aerobic respiration in an aerobic state, but are there any organisms that would still perform anerobic respiration even when shifted to aerobic ...
2
votes
0answers
34 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 ...
2
votes
0answers
30 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
53 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 ...
3
votes
1answer
70 views

How does heat generated by metabolism differ compared with heat generated through exercise?

I am from a mathematical background so I don't have much knowledge on biology. I'm building a mathematical model to predict heat generation with parameters of metabolic heat generation and exercise ...
1
vote
0answers
20 views

What is the site on an enzyme that binds either exitatory or inhibitory molecules? [closed]

A site on an enzyme where either exitatory or inhibitory molecules can bind is called a(n): A) electron transport site B) active site C) coenzyme D) metabolic pathway E) allosteric site If you ...
7
votes
2answers
689 views

Why are there so many medicinal plants?

Question Quite a few plant species can be used for medicinal purposes wiki. As an example, Filipendula ulmaria is rich in acetylsalicylic acid (aspirin). An allele that produces a substance which is ...
15
votes
3answers
5k views

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

The Japanese Wikipedia states that the average human body temperature is 36.0 °C (here,"ヒト"). The statement references the data from the Japanese government. Actually all of my Japanese friends think ...
1
vote
0answers
40 views

Are cold-blooded animals more energy efficient than warm-blooded animals? [duplicate]

When cold-blooded animals extract energy from glucose, do they do so in a more efficient manner than warm-blooded animals? If they aren't producing heat as a by-product, that would suggest that they'...
1
vote
1answer
37 views

Does exercising increase the rate at which UV rays are absorbed and cause affects?

Does exercising while in sunlight affect the rate at which the human body absorbs and reacts to UV rays? As sunburn is the secretion of fluids, increased dilation of blood vessels and inflammation of ...
2
votes
0answers
33 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
19 views

Glycoprotein hormones metabolism

Why do the carbohydrate groups in glycoprotein hormones decrease the rate of metabolism? And increase the half-life?
2
votes
1answer
25 views

Where does the lactate produced by tumors go?

Tumors are known to burn glucose and secrete lactate (this is known as the Warburg effect). Where does this lactate go? Does it steadily accumulate in the neighborhood of the tumor? This doesn't ...
6
votes
2answers
425 views

How efficient is the human body at metabolizing food?

My friend and I were having a discussion over how "efficient" human digestion is. If a human ate a 1000 calorie hamburger, how many of those calories (how much energy) does the body process into ...
0
votes
0answers
25 views

Diffusion coefficients of glucose in mammal tissues?

Where can I find estimates/experimental measurements of the diffusion coefficient of glucose in mammal tissues? Specefically I mean the inter-cellular space. I'm not looking for a specific tissue, so ...
2
votes
3answers
8k views

Why do we weigh less in the morning?

At first I thought it may be related to physics. You know, in one half of the day, the gravity changes, and the scale shows a different weight than the other. Then at night, gravity intensifies, and ...
6
votes
2answers
307 views

At any given moment, how much energy is stored in the human body as ATP?

At any given moment, approximately how much energy is stored in the human body as ATP in the ADP-P-bond? This of course depends on what type of cell it is and the activity of the individual in ...
14
votes
2answers
2k views

Do birds emit infra-red radiation?

I'm an electronics engineering student and I am going to use a sensor that detects infra-red emitted by birds that invade rice paddies. Do birds emit infra-red radiation?
8
votes
2answers
10k views

Does mixing alcoholic drinks really make you more drunk?

There is plenty of anecdotal evidence ("beer after wine and you'll feel fine, wine after beer will make you feel queer") that mixing alcoholic drink types leads to a stronger effect, but I can't find ...
0
votes
0answers
27 views

Is there any evidence to suggest that exercise reduces the side effects of caffeine?

I heard a friend say: I'm not drinking coffee this week. My body can only process the caffeine if I run at least 15km a week. I found this claim fascinating - that exercise temporarily ...
7
votes
1answer
87 views

About acetyl-coA in the Krebs Cycle of respiration

In respiration, Krebs cycle starts with acetyl coenzyme A which is made from pyruvate. However, it is said that the cycle keeps repeat it self with oxaloacetate turning back to citrate and cycle ...
0
votes
0answers
30 views

Can an inhibited enzyme be activated by an activator molecule binding to a second allosteric site?

Can the inhibition caused by a inhibitor molecule(ATP that attaches itself to an allosteric site of a subunit of the PFK-1) be reversed by the binding of an activator molecule (AMP that binds to an ...
1
vote
0answers
39 views

Why are carbohydrates the most common short-to-medium-term energy storage form in biology?

According to this table, gasoline has a specific energy noticeably higher than fat and more than twice that of carbohydrates; even short-chain hydrocarbons like ethanol and even methanol offer an ...
7
votes
1answer
108 views

How many, and how severe, are known single gene polymorphisms for obesity?

A fairly recent meta-analysis of studies examining the association between adult obesity and polymorphisms of the FTO gene (Peng et al., 2011). The paper looked at 59 studies and concluded that, "FTO ...
2
votes
1answer
130 views

Why would the citrulline content of the watermelon be so high?

Citrulline is a non-proteinogenic amino acid (that is, citrulline is an amino acid that is not coded for in mRNA), and it is an important metabolic intermediate in the Urea Cycle. The Urea Cycle is ...
1
vote
0answers
28 views

Can you change your gut microbiota by changing your diet? Would that affect calorie uptake?

I have seen peer-reviewed papers mentioning the daily changes in gut microbiota composition according to dietary changes. See for example this paper: http://genomebiology.com/2014/15/7/R89 My ...
4
votes
2answers
114 views

What's the point of glycolysis in fermentation?

In order to initiate glycolysis, 2 ATP are necessary. In the glycolytic process, you generate an additional 4 ATP, which results in a net gain of 2 ATP. If you don't undergo glycolysis, however, then ...
3
votes
2answers
727 views

Why would lactate be high in diabetics?

Why are lactate level high in diabetes? For example, type II diabetes are resistant to insulin. If those patients are insulin resistant their gluconeogenesis should be working at a high rate and, ...
0
votes
2answers
212 views

Why is succinate dehydrogenase attached to the inner mitochondrial membrane?

Succinate dehydrogenase is attached to the inner mitochondrial membrane. All the other enzymes of the Krebs cycle are located within the matrix of mitochondria, though. In biological systems, there ...
1
vote
1answer
61 views

What is the energy source for adipocytes?

Since adipocytes export fatty acids and glycerol and don't use them as an energy source, what is the main source of energy for adipocytes?
4
votes
1answer
1k views

How are non-glucose sugars metabolized in the body?

In my biology book's section on disaccharide metabolism and glycolysis, it states that sugars other than glucose must be acted upon to enter glycolysis. Let's take sucrose as an example. Sucrose is ...
4
votes
1answer
76 views

Can the kidneys utilize ketone bodies for energy?

Ketone bodies are water-soluble and should pose no problem to the kidneys because of solubility. If the kidneys are able to utilize ketone bodies for energy, then they must express the enzyme 3-...
4
votes
1answer
473 views

How is ammonia removed from the colon?

“Lactulose is also used to reduce the amount of ammonia in the blood of patients with liver disease. It works by drawing ammonia from the blood into the colon where it is removed from the body.” (...
1
vote
0answers
28 views

Is there a way to quantify in vivo cholesterol transport rates?

I have always had trouble grasping the physiology of lipoprotein cholesterol transport. The "standard" description found in the literature is that liver synthesizes cholesterol which is carried in "...
2
votes
1answer
1k views

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

I've heard that $NAD^+$ gains a Hydrogen proton during glycolysis and the Krebs cycle and becomes reduced to $NADH$. However, isn't reduction when a molecule receives an electron? Maybe I've been ...
5
votes
0answers
53 views

Is high metabolism linked to high evolutionary turnover?

I recently read The Dinosaur Heresies by Robert T. Bakker, a 1986 popular science book presenting arguments for an active lifestyle and high metabolic rate in dinosaurs. One of the arguments that ...
1
vote
0answers
52 views

In glycolysis, what is the source of the electron that makes NAD+ into NADH instead of NADH+? [closed]

I looked at the formula for the glycolysis reaction. The overall reaction seems balanced, however, I don't see anything on the left hand side of the equation that would provides the electron to ...
0
votes
0answers
33 views

Why is alcohol purged from the body more slowly when we sleep?

It is a popular belief that when you get asleep after drinking alcohol, in the morning you have higher level in your blood than if you stayed awake the whole night. Is this true? If so, why? Is it ...
3
votes
1answer
87 views

By what mechanism is NADP+ converted to NADPH in Photosystem I? [closed]

Here is my current understanding: $\mathrm{NADP^{+}}$ takes 2 electrons from Ferredoxin at the end of the electron transport chain to generate $\mathrm{NADP^{-}}$. An $\mathrm{H^{+}}$ ion in the ...
1
vote
0answers
21 views

How are muscle fibre size and oxygen consumption related?

Does anyone know of a paper which correlates the muscle fibre size to oxygen consumption in mammals? I am trying to find a correlation between muscle fibre type, size and (absolute and specific) ...