39
votes
Is the amount of the soil reduced when plants grow?
The vast majority of the mass of a plant is carbon-based which is obtained directly from the air via photosynthesis. So trees are, in a loose sense, solidified air!
And most of the mass that comes ...
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37
votes
Why don't viruses reach broad concentration outdoors in a city like allergens?
2, 4, 5, and 6.
6 being that the UV light (from the sun), fluctuations in temperature, humidity, wind etc mean that the virions are decayed relatively rapidly for most virus species.
To address (1): ...
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33
votes
Can bacteria be killed by purely physical trauma?
My (limited) understanding is that it is quite hard to avoid killing some bacteria even with very gentle physical manipulation. On the other hand, it is quite hard to use physical force to achieve ...
- 431
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-...
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27
votes
Accepted
Why is saltatory conduction in myelinated axons faster than continuous conduction in unmyelinated axons?
Short Answer
Myelination acts as an electrical insulator and allows saltatory propagation.
By reducing membrane capacitance and increasing membrane resistance, myelination increases the velocity of ...
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24
votes
Accepted
Can UV radiation be safe for the skin?
You're talking about long-wave UV, or UV-A radiation. In the 80s, experts claimed that this was a safe wavelength. Protection against UV-A was not part of sunscreen in the early days. Consequently, UV-...
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22
votes
Why don't viruses reach broad concentration outdoors in a city like allergens?
In another answer elsewhere on StackExchange, a poster estimated that there might be something like 100 g to 1 kg of SARS-CoV-2 virus worldwide, and that's an estimate of all the virus, including what ...
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21
votes
Accepted
What is the anatomical term for a two jointed leg?
Welcome to Biology.SE!
I think you are talking about plantigrade, digitigrade and unguligrade.
Please note that the number of joints in mammals does NOT vary, but only the relative length (and shape)...
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21
votes
Can bacteria be killed by purely physical trauma?
There are plenty of physical or mechanical methods of killing bacteria, but most are used in conjunction with other agents and probably don't qualify as "blunt force trauma". For example, ...
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17
votes
Why does UV radiation from the Sun cause skin cancer?
Rather than 'breaks' caused by high energy radiation, UV radiation causes chemical modifications of the bases ('letters') that make up DNA. There are four bases in the DNA alphabet abbreviated to A,T,...
- 1,415
16
votes
Accepted
What physical evidence exists that shows motor proteins "walking" within a cell?
Since you chose kinesins as an example class of motor proteins, I will also stick to them. In general, the movement mechanisms of kinesins are well studied and the general structure of kinesin ...
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15
votes
Why does UV radiation from the Sun cause skin cancer?
There are very many photochemical reactions: Up to 50–100 mutagenic reactions on DNA per second might occur in a skin cell during exposure to sunlight, but are usually corrected within seconds by ...
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9
votes
Accepted
How does membrane potential vary between intraceullar membranes and the cellular membrane?
Yes, various intracellular membranes do have potential differences, but as you can imagine they are more difficult to measure experimentally, so in general data on this is scarce.
Summary
...
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9
votes
Accepted
How much energy does a small spider expend per day just waiting for its web to vibrate?
Short answer
Approximately 240 J on a daily basis.
Background
Ballesteros et al. (2018) modeled basal metabolic rates of insects. They reckoned that endotherms, like insects, basically use energy ...
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8
votes
Accepted
Would the human body react faster to touch or sight
A "touch" or "haptic" sensation will be much faster due to several reasons:
Haptic feedback can be processed without the presence of any higher-order cognitive processing, therefore meaning that the ...
- 2,603
8
votes
Can any organisms see non-electromagnetic radiation?
Some fungi have radiotropism; they grow toward radiation sources. Melanin-expressing (melanotic) fungi migrate toward radioactive sources, which enhance their growth. According to this paper.
These ...
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8
votes
Accepted
Should there be separate Ramachandran plots for an amino acid in different contexts?
The phi and psi dihedrals describe the dihedral on both sides of the c-alpha of a single amino acid, and do not involve any angles of the neighboring amino acid.
The Ramachandran plot is something ...
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7
votes
Why don't membrane proteins move?
No other answer has mentioned this so I created an account just to say this.
Some membrane proteins do not move. This is because they are fixed in that position in the membrane due to the ...
7
votes
Accepted
Is Einstein's mass energy equivalence ($E=mc^2$) relevant to biological systems?
Short answer
Any law of physics will of course be applicable to living beings. However, in the absence of mass gain and mass loss, the input = output equation for ...
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7
votes
Is the amount of the soil reduced when plants grow?
The soil is the source of a small quantity of vital elements like magnesium (component of the chlorophyll), phosphorus (DNA), sulphur (some proteins) and more. As the plant grows, these are removed ...
7
votes
Accepted
What is the biological potential for vision of wavelengths outside the human visual range?
There are some limits on what light can be detected biologically based on physics and chemistry. Although there are animals that can sense more UV or more infrared than humans, they are still subject ...
- 44k
7
votes
Accepted
Are there known life forms that are able to transform mechanical energy into chemical energy?
There are no known life forms that use mechanical energy as a primary form of metabolic energy (i.e., for generic cellular functions). Many life forms are sensitive to mechanical disruption in some ...
- 44k
7
votes
Accepted
Difference between prions and amyloid proteins?
Amyloids are protease resistant insoluble fibrils formed because of (mis)folding and aggregation of soluble proteins (Rambaran and Serpell, 2008, Sabate et al., 2015). The first definition of prion ...
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7
votes
Can UV radiation be safe for the skin?
There are (at least) two sides to this story. One is direct DNA damage being caused by UV-B light which happens to have photons with just the right amount of energy to interact with thymine. This has ...
- 259
6
votes
How's the membrane potential restored to resting state after hyper polarisation?
The Na,K-ATPase restores negative membrane potentials. When a cell is hyperpolarized, leaky K+ channels take care of that. Leaky K+ channels are always open. Generally, K+ has the tendency to diffuse ...
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6
votes
What is the transmembrane 'Positive-Inside Rule' nowadays? Has the definition changed over time?
I think you have misunderstood the "inside" part of the "positive-inside rule". Perhaps because "inside" is indeed an imprecise term (but now it is history and cannot be changed ;) ). In order to ...
6
votes
Why don't membrane proteins move?
There are two types of proteins that are present in a membrane, because you have not been specific about which type of protein you are talking about I will consider that you are talking about Integral ...
- 126
6
votes
Is Einstein's mass energy equivalence ($E=mc^2$) relevant to biological systems?
No, the mass-energy convertibility has no practical relevance to biology. The amount of mass produced or lost in the chemical reactions in biological systems is so small as to be immeasurable and is ...
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6
votes
Are there known life forms that are able to transform mechanical energy into chemical energy?
This is definitely not my field, and I have no interest in science fiction, but the question struck me as interesting, and brought me to an area of bimolecular science that may be relevant to the ...
- 24.3k
6
votes
Accepted
What is meant with “the chest wall and lungs are coupled together”?
How are the lung and chest wall coupled?
You have your answer in the text:
the surface tension between the lungs and the chest wall
And as you say, it is very much
like there is a physical-...
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