133
votes
Accepted
Why is the heart not in the middle of the body?
First of all, let me make it clear that the heart is at the vertical centre of the body -- it is not shifted towards left (or right). However, it is slightly tilted towards the left in most cases.
...
52
votes
Accepted
Why are bruises not lethal?
blood clots inside the body have an unfortunate tendency to get into the bloodstream and cause blockages, leading to severe problems such as strokes or heart attacks
This statement is primarily true ...
51
votes
Accepted
Why does cutting onions cause tears?
Interesting question! The cause of tears and itching is the chemicals produced by onion (Allium cepa). Lets go into some details.
Onions, coming from the family Liliaceae (also containing garlic, ...
51
votes
Accepted
Does any molecule other than DNA have a double-helical structure?
A few examples:
Starch
A polymer of glucose that can form a double helix and functions primarily as energy storage in plants.
[image source]
f-Actin
Filamentous actin forms a helical structure with ...
45
votes
Why isn't Fluorine, or Neon, the final electron acceptor in cellular respiration?
One of the main reasons that modern(!) biology uses oxygen as an electron acceptor is availability.
Around 2.45 billion years ago, oxygen (O$_2$) started being built up in the atmosphere (which ...
41
votes
Accepted
Do photosynthesis and respiration violate the law of conservation of energy?
With slight adjustments to the scientific wording, what the poster states is in effect:
“…to produce one molecule of glucose in photosynthesis, 18 ATP molecules are used up hydrolysed”
and
“…...
40
votes
Why do some vegetables taste bitter?
Nice question! Many vegetables taste bitter because they contain compounds known as phytonutrients (Greek phyto = "plant"). There are more than 2500 phytonutrients known, and the most important (and ...
38
votes
Killing enveloped viruses with soap
Soap molecules are amphiphilic. This means those molecules have parts which are hydrophilic (water-loving, or "polar") and parts which are hydrophobic (water-avoiding, or "non-polar&...
37
votes
Accepted
Do all proteins start with methionine?
You are correct in thinking that since the translation of mRNA begins with AUG, which codes for methionine, then all proteins should contain a methionine at their N-terminus (aka start site). But, it ...
36
votes
Why are bruises not lethal?
@Bryan Krause's answer is quite correct. I just want to clarify what a bruise is, because I think you have a misconception of what happens.
There are bruises (blood leakage into tissue because of ...
35
votes
Accepted
Why do animal cells "mistake" rubidium ions for potassium ions?
There are multiple biological mechanisms that can be brought to bear for distinguishing between atoms. In addition to binding properties (e.g., ionic charge, electronegativity, bond strength), there ...
34
votes
Accepted
Is atmospheric nitrogen chemically necessary for life?
To get soil nitrogen in the first place, nitrogen fixation is necessary which takes atmospheric N2 and converts it into biologically useful forms.
Nitrogen fixation is performed by bacteria and ...
32
votes
Accepted
Why don't membrane proteins move?
Proteins can move around the membrane.
Most proteins do move within the membrane. The membrane is a liquid crystal and has fluid behaviour. Specifically, this is due to the membrane being in a gel-...
32
votes
Why isn't Fluorine, or Neon, the final electron acceptor in cellular respiration?
Availability and applicability.
Availability.
In the beginning, there was CO2. It was abundant in the atmosphere, and later, the oceans.
Fluorine and neon weren't, and so respiration evolved around ...
30
votes
Accepted
Why do mints make your mouth feel cold?
The feeling of cold from mints is caused by menthol. Menthol affects the TRPM8 receptor on skin and also in the mouth. TRPM8 is also a general cold receptor: so if you are in contact with menthol the ...
29
votes
Is antivenom fatal?
1. Synopsis
I'd like to preface this by saying don't randomly use medicines without a doctor's advice. It's fairly unlikely antivenom would cause you any harm but in some cases, antivenom could be ...
28
votes
Accepted
Why are sushi proteins called "sushi"? What are the origins of this name?
Because their shape reminded researchers of rolls of Sushi (Ichinose et al, 1990):
These repeats were initially called GP-I structures because they were first identified in $\beta_2$-glycoprotein I....
28
votes
Accepted
Can plants suffer from CO2 poisoning?
Short answer
It has been shown that plants may already suffer from doubling the atmospheric CO2 concentration from 340 to 610 ppm, something that might happen during the next hundred years or so based ...
27
votes
Are stable isotopes ever used in pharmaceuticals?
Deutetrabenazine.
As the linked article from Wikipedia notes:
Deutetrabenazine (trade name Austedo) is a vesicular monoamine
transporter 2 inhibitor which is used for the treatment of chorea
...
26
votes
What does it mean to "write an image and GIF into the DNA of bacteria"?
The image was not in the DNA as such, only as an abstract representation that could be converted into an image from knowledge of the code. Briefly, they encoded the image into DNA, using a couple of ...
25
votes
Accepted
Can fever cure Ebola disease?
Short Answer: Fever cannot cure Ebola simply because the virus is not temperature-sensitive.
Background: Fever is a defense mechanism of the body which is specific to temperature-sensitive virus and ...
22
votes
Why does cutting onions cause tears?
This is due to a lachrymatory agent called as syn-propanethial-S-oxide.
The process goes as follows:
Lachrymatory-factor synthase is released into the air when we cut an onion.
The synthase enzyme ...
21
votes
Accepted
Is cancer caused by vitamin B17 deficiency?
Short Answer: No.
Background: First of all, there is no such thing as vitamin B17. The compound, amygdalin or laetrile, which is referred to by this term, is not a vitamin1. Amygdalin is indeed a ...
21
votes
Accepted
Can a human be made with ovum but without sperm?
Nice question! It is actually very difficult to do so because humans, obviously, are far more complex than some animal species which naturally show parthenogenesis. Just to mention, there are female-...
20
votes
Accepted
How do ants follow each other?
The chemical we are talking about here is called pheromone, trail pheromone to be specific.
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the ...
20
votes
Accepted
Is NMDA produced in the body?
(my comment reiterating the answer seemed useful, so I've reproduced it here)
There are "NMDA receptors" in our body. There is not NMDA naturally in our body*. "NMDA receptor" is just a name people ...
20
votes
Accepted
Why is protein turnover necessary or important for cells to function?
Biology is an intricate orchestration of chemical reactions and their products. Generally, this fete is accomplished by enzymatic facilitation of certain reactions that would otherwise occur too ...
18
votes
Accepted
What stops messenger RNA from binding to itself?
It does fold on to itself. There are secondary structures in RNA and some of these secondary structures also have regulatory functions (for example, riboswitches). Some of these structures can also ...
18
votes
Accepted
How do ion channels transport only specific ions?
I am restricting the answer to only $Na^+$ and $K^+$ channels, assuming similar mechanism for other channels. In these 2 channels, such high level of specificity is achieved because of two main ...
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