Questions tagged [biophysics]

The use of methods from the physical sciences to aid in the study of biological systems. Note that biophysics questions are only allowed if they are mainly about physics.

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18 views

Statistical mechanics applied to biology [closed]

is there anyone expert in statistical mechanics applied to biology, in particular in the WSME model? Thank you
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4answers
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Can viruses be in a superposition? [duplicate]

I know that atoms and entire molecules and even sets of hundreds of molecules can be in superpositions of position eigenstates. Viruses are the smallest living organisms (if they can even be called ...
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Physically, how does erection work?

All articles I found explain a human male erection through biological mechanism. However I am still curious how such process can make the male sexual organ "stand up" during an erection. ...
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When I just move my hands around, how is the momentum being conserved?

I guess when I'm moving my hands around, the electrostatic potential stored in the chemicals in my body is converted to motion of my arms? But what about momentum conservation? I think the brain sends ...
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What modern mathematics/theoretical physics can one use in mathematical biology/biophysics, especially genetics and high resolution microscopy? [closed]

I’m interested in theories involved or would be involved in current or near-future biophysics/mathematical biology, so I’m wondering that 1.what modern mathematics/theoretical physics one can use in ...
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How important is floating-point precision in molecular dynamics?

I'm wondering how important floating-point precision is in numerical simulations of molecular dynamics in biology. From what I understand, molecular dynamics programs like NAMD use 32-bit floats to ...
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Why we only see black colour when there is no light? [closed]

pls help me on it. I do not know if it is right but why do we only see black colour while there is no light.
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How do I calculate the effort force exerted by my hands while holding a high plank? [closed]

This high plank is an example of a 2nd class lever. The fulcrum is at the feet, the load is at the centre of gravity of the body, and the effort is at the hands. If I know: My weight (the load force)....
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IR and UV transmissivity window of the (human) eye

Given this image: I just assume that the eye is made out of glass, so I wonder how is it that IR and UV radiation is absorbed by it? I would understand one of them but why is it transmissible for ...
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Trying to figure out the mathematics behind the classical superhero lift-by-the neck [closed]

I recently got into a debate about the classical villain or hero move of lifting an adversary by the neck. We've all seen the one-arm or even two-arm lift and i made the case that even two arms ...
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Do adjacent sarcomeres oppose each other during contraction?

A sarcomere is the contractible portion of the muscle cell. And here is a figure of three sarcomeres in series before and after contraction: I was taught that the thick fiber, myosin, pulls on the ...
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What is the entropy difference between $n$ free-floating amino acids and $n$ amino acids that have been translated into a protein?

Is there any known calculation for the (~ average) change in entropy between $n$ free-floating amino acids in a cell, at typical physiological concentrations, versus those same $n$ amino acids after ...
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Non-Conservative Potential for Charged Residues in Proteins

I am struggling with this question. I want to determine whether the potential of a protein is conservative or not if its dielectric constant depends on the local density of the protein. My model only ...
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By what mechanism is a growing tree root able to lift heavy concrete pavement?

A tree root lying under several square meters of 100mm thick concrete pavement can cause the pavement to lift up as it grows. What forces are involved in creating this lift? I vaguely understand that ...
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In what situations do throwing an object use less energy than carrying it? [closed]

This relates to humans carrying or throwing rocks, so it relates both to mechanics and biophysics. Let's say you stand at point A where there is a pile of rocks. You need to get the rocks to point B. ...
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How does a spectrum analyzer works. Example with particular case: eyes [closed]

[edit]: I reformulated my question to first talk about general spectrum analyzer and then ask about how vision works (which is a particular case of spectrum analyzer as I explain below). Let's assume ...
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What equation can we use to describe flow through a thin mask with through-holes?

What equation can best describe the flow of water through holes (500um) within a thin mask (200um)? I don't think the Hagen–Poiseuille equation applies here, since the hole size is big relative to it'...
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What forces are there against the motion of walking or running?

When we walk or run, are there any forces that counteract the static friction between our feet and the ground? I can’t seem to think of any, but if not, why is it that we still need to push on the ...
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How does the Brownian motion of air molecules compare to the threshold of human hearing as a function of frequency?

This fantastic question essentially asks what is the noise floor of air? Both the answer given on that thread and the value stated by Microsoft are around -23 or -24 dBSPL. However, overall loudness ...
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1answer
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What is the basic physics mechanism behind photosynthesis? [closed]

Could a similar process be achieved artificially in a laboratory, with the same near perfect efficiency biological systems display. Is there a sound simple theoretical model on how this works?
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Why does minimization of free energy result into an almost uniform distribution of protein foldings?

I have just found out that proteins (at least in some cases) are folded into their functional conformation (i.e. their functional folding), through thermal fluctuations, and that this conformation ...
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What determines the mathematical relations between energy use, axon thickness, and firing rate of action potentials in a neuron?

I have a naive model of action potential energy use and I’m unsure where the model is wrong. Clearly the model is wrong because its conclusion is wrong: When an action potential moves along an axon, ...
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198 views

Why can't we jump very high?

If somebody is able to output $3750$ $\text{N}$ lifting weight on the back doing squats, why can't they jump at $150$ $\text{km}/\text{h}$ without weight? With weight: $$(300 \text{ kg of load} + ...
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Has physics ever tried to explain how do we get “sensorial experiences”? [closed]

To be clear about what I mean with "sensorial experiences", let's take for example our visual experiences. Certainly, physics (and other sciences) explains a whole process which involves light ...
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Is 260 picoampere sufficient to transmit a signal through an axon in a nerve?

Would 260 picoampere be sufficient to transmit a signal through a 1 meter long axon in a nerve, with a diameter of one micron? There is context to why I ask this, but, because of failure to interpret ...
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How nerve signals preserve quantum coherence?

Roger Penrose in this interview says he was trying to find out "... how it is that nerve signals could possibly preserve quantum coherence". What does he mean by that?
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Do organism produce more entropy as they get more complex i.e. does biological evolution mean decrease in efficency? [closed]

Consider a cell. It has more efficiency than a human being even though a human being is a bulk of cells: The cell has fewer losses when it converts the food it ate for nutrition to do some sort of ...
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Could A Stray Radioactive Particle Collide With an Atom in a Human, Causing a Cascade?

I'm not thinking of even particles from a nuclear power-plant or man-made event. If a high-velocity highly-interacting particle made it through all the natural protections that keep life in a non-...
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Using particle physics math model to simulate simplest life [duplicate]

We still don't know many thing going inside living cells so I'm wondering whether it's possible to create a math/computer model operating on basic known particles (or higher level composite particles ...
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Is a human one thing not larger than one atom, yet he can sense where his body is touched, or he is not one thing, or atom is not the limit of size? [closed]

For example, a human can sense if their head or toe is touched and the distance between his head and toe is more than the size of one atom; is that human one thing not larger than one atom, yet ...
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Kullback-Leibler divergence as a measure of irreversibilty?

I watched this recent KITP webinar on Nonequilibrium thermodynamics for active matter yesterday. I saw that KLD(Kullback-Leibler divergence) is used as a measure to quantify irreversibility in the ...
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Biomechanics statics of an push-up [closed]

So I am really struggling with a statics problem about calculating forces and torques of an exercise. So I need to calculate the forces acting on the feet and hands, as well as the torques, for 2 ...
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Why we don't work physically when we don't make something move? [duplicate]

The formula for Work is F*x, where x is distance taken. So by physicially work formula, why don't we experience any work if we do not make any object move? Is there a specific reason? Example, I am ...
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Is there a use of the SI units gray, sievert and katal in pure physics

Since the gray and the sievert are associated with relative biological effectiveness of the radiation and the katal is associated with catalytic activity, do the gray (Gy), sievert (Sv) and katal (kat)...
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Why do small animals appear to move faster than larger ones?

I am keen to understand why smaller creatures move relatively faster than larger ones. Not only do they move faster, but their metabolism runs at a faster rate, they seem to process information faster ...
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Plausibility of detecting viruses using optical spectra [closed]

Ok, this is a huge long shot, and I also apologise if this is a poor question (I'm a newbie here...). This doesn't seem to me a strictly perfect fit for Chemistry.SE, Biology.SE, or Photography.SE ...
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What would the graph look like if the electrodes were non-equidistant from the dipole?

Hypothetically speaking using the diagram above. If the negative electrode was very far away from this excitable tissue and the positive electrode was right next to it. What would the voltage graph ...
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Chloride equilibrium potential is negative shouldn't it be positive?

Chloride flows down its concentration gradient into the cell. At a certain point a minute amount of net positive charge develops on the outside, enough to electrostatically attract chloride ions back ...
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Why are our feet fixed when walking?

Why are our feet fixed when walking? Why does the static frictional force acting on our feet not push our feet forward ?
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Physics-based Demonstrations for biology students

I am looking for resources where physics concepts relevant to biology are explained in simple terms by actual experiments or virtual animations. The site should be suitable for freshman students with ...
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Is there a minimum principle which governs neuronal activity in brain function? [closed]

Reinforcement learning is a well established field which attempts to explain the behavior and decision-making of toddlers, among other agents. The core principle of this theory is based on dynamic ...
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Are vibronic coherences, vibrational coherences and electronic coherences types of quantum coherence or classical coherence?

I am doing a research project on whether quantum coherence is involved in how light energy is transferred after the initial absorption of light during photosynthesis. I have found a research paper ...
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Effect of deep-sea pressures on whales vs humans — how do whales survive?

I believe that humans would be crushed by the ocean at depths that whales regularly dive to. I know that the pressure per square inch is very high but whales can survive, I read, because of various ...
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What causes the diffraction resolution limit of a protein crystal?

My question regards diffraction patterns and resolution limit of protein crystals. I understand that the inner symmetry (i.e. arrangement of the macromolecules) in a protein crystal determines how ...
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1answer
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Where does the activation energy for ATP come from?

ATP provides the energy for energy-consuming endergonic reactions, for example to power a molecular motor. The reaction is: $$\text{ATP}+\text{H}_2\text{O}\to \text{ADP}+\text{P}_i+\text{free energy}$...
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Isovolumetric pressure changes in blood during ventricular contraction

Some background to set up the problem. Blood flows into the left atrium via the mitral valve and leaves through another valve, the aortic valve. There is a moment in the cardiac cycle where these two ...
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Hyperspectral Imaging

Is it possible for a HSI camera to detect how long back a particular wound occured in the body? Eg: There's a body for postmortems with some marks/wounds at some places, can a HSI camera help us in ...
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Why don't we see the violet in the rainbow as blue?

I understand that we perceive the sky as blue and not violet because (1) sunlight has more blue than violet in it (see here), and (2) our eyes are more sensitive to blue than to violet. However, I ...
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Human infrared emission resonance [closed]

I understand (please correct if misinformed), the human body generates approx 100W of infrared energy, which seems (to an old engineer) an incredible amount of energy from a biological. In recently ...
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Force produced by muscles proportional to area or volume?

I've heard it said that the force a muscle can exert is proportional to its cross-sectional area. It seems to me it should be proportional to length also. If you have someone pulling on a large block, ...

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