This tag is for questions about the general biological features of human beings (as opposed to the biology of non-humans).

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Cellular aspartate level?

I know that aspartate is a product of urea cycle, gluconeogenesis and oxaloacetate. In addition, there are dietary sources such as meat and vegetables. I would like to know what are the other factors ...
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0answers
60 views

Why is my right hand's thumb on the left side and my left hand's thumb on the right side?

My daughter just asked this question, and I could not provide a thorough answer. My first speculation is that it allows one to manipulate an object using one' both hands simultaneously (if the thumbs ...
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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
74 views

Is it possible to grow a fertilized human egg entirely outside the woman's womb?

Many science-fiction movies show the possibility of growing a newly fertilized human egg entirely outside the womb of the woman. This means that you have to create the exact circumstances for the ...
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2answers
262 views

Are unilaterally deaf people able to determine where sound comes from?

My question is on people deafened in one ear, but normal hearing in the other. Time and level differences between the two ears are only part of how the human body can localize the source of the sound....
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1answer
19k views

What is the composition of human feces?

Are there any studies or general information on the composition of human feces? I'd specifically like to know the percentage of carbohydrates and amino acids relative to the amount that was ingested ...
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2answers
64 views

What physical traits are derived from the Neanderthal DNA in human DNA?

Some researches had found that Human DNA has a bit of Neanderthal DNA. So they suggested there would have been crossing between Homo sapiens and Neanderthals. Now the Neanderthal looked a bit ...
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2answers
67 views

Does night sleep provide more energy-regain than sleep during the day? [closed]

After reading this, I know that sleeping is an universal function, and that basically everything with a brain has the need to sleep. However, I am still confused to what extent it is necessary to ...
14
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1answer
953 views

I don't want to know what bacteria is called but if the bacteria from unborn babies have benifits on health? [duplicate]

This question is not the same as the duplicate. I was told that when babies are born they are born with bacteria in their stomach. When a child takes antibiotics are there unique bacteria destroyed ...
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2answers
81 views

Use of sunlight in biological processes

Sunlight is used by green plants in photosynthesis, but it is also used by animals in the synthesis of Vitamin D. Are there any similarities between the two processes and how is the light energy ...
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0answers
21 views

How much yogurt would one have to consume to have a noticeable effect on neurotransmitters [closed]

I read several recent articles that proposed a link between bacteria in our gut and neurotransmitters in our brain. For instance http://www.ncbi.nlm.nih.gov/m/pubmed/24997036/ I am curious how much ...
13
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3answers
471 views

How does a person get AIDS?

I am inquisitive to know about how a person contracts AIDS. Among the common masses it's still the belief that having sex with multiple partners causes the disease but that is not the case when read ...
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0answers
24 views

How do I “reinoculate” a petri dish with new bacteria?

Hypothetical question, intended to find a general procedure rather than case-specific recommendations: I have a petri dish full of growth medium with a large population of gram-negative, anaerobic ...
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0answers
52 views

Why is a wound much more painful when damp?

Why is a wound much more painful when damp? This is a very strange phenomenon. For example: I have a little wound, not painful at all. But, when it is just damp, it is much painful.
5
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1answer
138 views

How do omega-3 fatty acids reduce cholesterol at the molecular level?

I have heard that omega-3 fatty acids found in fish are a good way to prevent/reduce cholesterol problems. My question is how do omega-3 fatty acids do that: what are they doing on a chemical level ...
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0answers
12 views

How large are medullary thymic epithelial cells in volume?

I'm looking for a rough average volume of medullary thymic epithelial cells (mTECs/MECs) in humans and mice. It would also help to know how they differ in form (are they spherical, long stretched, ...
6
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1answer
75 views

Why is there no symmetry in pigmentation when comparing people north and south of the equator?

If you are at the equator and start moving north, the further you travel, the lighter the skin of the indigenous peoples. Considering that we live on a ball, why do we not find the same traveling ...
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0answers
17 views

Relationship between Human Sleep Cycles & Sunlight

What is the relationship between the human sleep cycle and Sunlight? Why do humans tend to sleep for longer hours during the night than the day. Since we rely on Artificial lighting during the night ...
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0answers
44 views

Are all the atoms in your body replaced with others over a 30 year period?

I was reading Creation - Life and How to Make It by Steve Grand. (This is the book that inspired Jeff Bezos to start the AWS initiative. ) In it he makes the following statement: Anyhow, by now I ...
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2answers
958 views

What is the cause that angina pectoris is felt in your left arm?

When someone has heart problems sometimes they feel pain in their left arm. But why is the left arm painfull?
2
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1answer
63 views

Fasting gastric pH versus normal gastric pH

I want to know if someone is fasting (no food or drink for a whole day) will they have a higher or lower pH than a person who is eating regularly? If so what is an estimate of both of those pH's in ...
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0answers
16 views

Is it true that our tooth enamel shows a 7 days rhythm?

Is it true that in fossil remains of the Turkana Boy a kind of growth rings are found in tooth enamel which have a rhythm of a week? This also appears to apply to other primates? If so what is the ...
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1answer
170 views

If human proteins are synthesized from only 20 different amino acids, then how can there be such variety of proteins in human cells?

I know that human proteins are synthesized using only 20 different amino acids. However, how can there be thousands of different proteins in human cells, if we only use 20 amino acids to make them?
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0answers
23 views

Are there biological safeguards to compensate for male primate infertility?

I'm trying to understand human sexual selection, and the following question has been on my mind for some time. I don't know the exact terminology to do a quality scholarly search on the subject. Are ...
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3answers
2k views

What would happen if one eats silica gel?

What happens if one actually does go about eating the beads in those "do-not-eat" packets?
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1answer
43 views

Why does the blood not clump and result in death?

In this question's accepted answer, it is said that the blood type will slowly change to that of the donor's. When the blood in the person is about 50% his own and 50% that of the donor's. i.e, 50% A ...
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0answers
20 views

What kind of cell has the most different receptors?

All hormones and neurotransmittors has their own receptor. Now some of the cells has a few different receptors but others has many sorts of receptors. So what are the most receptive cells? Are that ...
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1answer
130 views

Does our immune system react on all bacteria?

In our body we carry a lot of bacteria. Some of them are bad for our health, but others are beneficial. For example bacteria may protect us against other pathogenic bacteria. But is our immune ...
12
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2answers
171 views

Can viruses be toxic?

Bacteria can produce toxins like endotoxins and exotoxins. In diseases like cholera or tetanus they can harm infected people due to these toxins. Now, although viruses are much smaller and are ...
3
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1answer
104 views

Which literature/study/myth spurred the idea that urine is sterile?

There is a seemingly unfounded mantra that a person's urine is sterile who is not suffering from a UTI. So far I have found convincing evidence to the contrary; urine is not sterile. This poster ...
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0answers
37 views

When touch and pain are caused by heat/cold or pressure how are the nerve cells triggered?

I suppose that when your skin is smoothly touched by any cold/heat or pressure we feel that because our AB cells notice this due to a kind of change in the nerve cell. But when you touch something ...
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0answers
14 views

Does the change in eye color (melanin concentration) affect the iris pattern?

In cases of acquired heterochromia, is there a quantifiable change in the iris pattern; the clefts , furrows, etc. If yes, what changes are observed? And if no, are there any diseases or acquired ...
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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 ...
5
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1answer
59 views

If our skin is burned by the sun what causes the red color of the skin?

Mostly it is not a good sign we are burned because too much UV light has damaged our skin and increases skincancers. But the red color we get after a few ours, what is the exact cause of it and why ...
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1answer
76 views

Corpus luteum during the luteal phase and gonadotropins

Does the corpus luteum operate independently of the hypothalamic-hypophyseal-ovarian axis? I know that hCG sustains the corpus luteum in the absence of FSH and LH, but in an ovarian cycle where there ...
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1answer
36 views

the evolution of the human brain size [closed]

I was thinking, as I know, sometimes the process of producing DNA did not work well(correct me if I'm wrong), so it gives us some changes in the object we gonna ...
0
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1answer
146 views

Is an athlete's heart rate after exercise greater than a non-athlete [closed]

I was just wondering And if it is greater or lower how does this benefit an athlete Also what is the averaged number of heart beats per minute
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2answers
119 views

Are humans evolving since their first appearance? [duplicate]

Is the evolution a very prolonged progress, or are we going to witness further evolution of the human species? If so, in which direction? Are there any widely predicted changes for humans?
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4answers
16k views

How many genes do we share with our mother?

Somewhere I have read we share more than 99% of our genes with every other other person and 98% of our genes with chimpanzees. What does this mean? Don't we share 50% of our genes with our mother and ...
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1answer
29 views

Can specific B-cells be created in a lab? [closed]

Instead of creating protein sequences, could that stepped be skipped and just have B-cells created to manufacture a particular type of immunity?
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2answers
6k views

How do we know that everybody's DNA fingerprint is unique?

How do we know that everybody's DNA fingerprint is unique? I know, I know, everybody's DNA is unique. But when we do DNA fingerprinting, we're looking at very specific regions of high variability. ...
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1answer
5k views

Why do sneezes come in pairs or more?

I very rarely sneeze just once, usually there's two coming in a row, and I've noticed the same thing in other people and even in animals. Is there any reason for this?
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5answers
16k views

Why is cold water more refreshing than warm water?

Obviously, the temperature of water does not affect its chemical composition. At least not in the ranges we are likely to drink it in. Yet it is clearly far more pleasant and refreshing to drink cool ...
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1answer
44 views

Does a zygote express all genes?

If a zygote has all the cytoplasmic determinants and all the specific transcription factors, does that mean that all genes in the genome are expressed?
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0answers
70 views

What Would Happen To a Human Who Died In Space And Stayed There For a Prolonged Period of Time? [closed]

Last night I was watching a documentary regarding the Apollo space program, and it spoke about how Apollo 8 orbited the moon 10 times then came back to Earth. It said that while the ship was in orbit ...
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0answers
40 views

Is the zygote the only totipotent cell?

I’ve been told that the unfertilized egg contains cytoplasmic determinants (e.g. proteins, transcription factors, mRNAs) that are divided unevenly during the early stages of cell division in an embryo....
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1answer
13k views

Will a bone marrow transplant change one's blood type?

Will a bone marrow transplant change one's blood type? Or is the donor blood type matched with the person before transplant?
5
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0answers
118 views

What will happen when humans are injected with plant growth hormones

Will plant growth hormones (PGHs), (let us consider auxins for example) poison our body or not? I do realise that when you eat a shoot, auxins get digested and are less likely to be poisonous but when ...
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0answers
54 views

Are high sounds worse for your hearing than low sounds?

From about 80 dB it is possible to suffer loss hearing after a couple of hours. But does it make a difference what frequencies those sound waves are or is it just the volume of the sound in dB that ...
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2answers
80 views

Do babies conceived naturally or artificially have any differences in long-term health?

Are there any long-term differences in children conceived via artificial insemination or sexual intercourse, pending that the mother successfully delivers the child?