Questions tagged [biophysics]

The use of methods from the physical sciences to aid in the study of biological systems.

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How badly will warmer air affect birds' ability to migrate long distances?

I recently read about how warmer air decreases lift for airplanes. I wondered whether birds would also experience reduced lift, and whether that might make it harder for them to migrate long distances....
vknowles's user avatar
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Does thermal shock apply to human bones?

I always knew that a drop of cold water would crack a hot glass. But does this apply for our bones tho? Obviously not instantly, but after repeating it for years? I've always wanted to do cold showers ...
Mohammed Ibrahim Daghbouche's user avatar
2 votes
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61 views

Do hair cells in the ear also vibrate at frequencies outside our hearing spectrum?

(The question has its origin because I asked myself in how far frequencies outside our perception can harm our hearing.) First of all, the energy of a mechanical wave (in this case, the sound wave, ...
iwab's user avatar
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Is there a detailed model of the resonance of the basilar membrane and excitation patterns of hair cells?

I've read that it's generally understood that deeper parts of the cochlea are sensitized to lower frequencies, and regions closer to the oval window are sensitive to high frequencies. In a sense, a ...
trbabb's user avatar
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2 answers
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Efficiency of molecular motors vs. human-made motors

On the wikipedia page for "Molecular motor", it says "In terms of energetic efficiency, this type of motor can be superior to currently available man-made motors." without any ...
nullspace's user avatar
-1 votes
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Can Sleeping With Reptiles Reduce Excess Body Heat from Your Partner? [closed]

I'm an engineer and biology is my weakest point, so please forgive if this question is dumb. My wife always complains that I set the air temperature too cold at night. She's exothermic in a number of ...
James Strieter's user avatar
1 vote
1 answer
64 views

Need biological system with specific reset process

I need a biological process that can be described as a stochastic process in statistical physics. I am familiar with some processes such as birth-death or gene expression, but now I need a process ...
caren's user avatar
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Action Potential and Impulse Direction

My textbook describes generation of action potential due to an "induced increased membrane permeability to $Na$+ ions" and presents the ad hoc fact that electric current would flow from the ...
Feldsmithonian's user avatar
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Absorption bands of chlorophyll

I am currently reading this article, which discusses the functional impact of the $Q_x$ and $Q_y$ absorption bands of chlorophyll in photosynthesis. However, the article didn't say where on the ...
slithy-tove's user avatar
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Bernoulli's theorum and the circulatory system [duplicate]

I learnt that when an artery is constricted, the blood pressure in the artery increases, but if the diameter of an artery decreases, the velocity of blood through it increases (the continuity equation)...
Gokul L's user avatar
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Primary charge separation in Photosystem II

I was reading through an article about primary charge separation in Photosystem II when I came across the following graphic: I assumed that the axis is measured with respect to the unexcited system, ...
slithy-tove's user avatar
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Does lower stomatal conductance of water influenced by elevated CO2 decrease overall evapotranspiration?

From what I understand, elevated CO2 levels decrease the stomatal conductance of water in plants. What I remember from irrigation sciences, higher temperatures should be more demanding on ...
Lukáš Tůma's user avatar
2 votes
1 answer
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Why do humans see exactly one octave of light?

The visible spectrum of light is often defined as 350nm to 700nm. On Wikipedia, it says 380nm to 750nm. Either way, the upper bound is very close to double the lower bound. This means humans can see ...
Lycodo's user avatar
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Pressure inside a cell

In this article, in the introduction 3 paragraph first line they said: The flow of water plays a critical part in these processes. Recent experiments suggest the pressure equilibrates within cells ...
Remember's user avatar
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-2 votes
1 answer
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What are the mechanical properties of human skeletal muscle?

TL;DR: I need more information on the mechanical properties of human skeletal muscle; if you have such information, please give it to me. I'm writing something on how much more effective (or otherwise)...
KEY_ABRADE's user avatar
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conduction in unmyelinated axons

(Not a specialist here) Several questions touch the voltage propagation along an unmyelinated axon, but I'd like to focus on the following. How fast does the voltage of a sub-threshold perturbation ...
scrx2's user avatar
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Should soundscape ecology be a component of STEM education? [closed]

I'd like to see soundscape ecology be included in STEM education. I realize there is so much to teach and so little time, but think that primary and secondary students would be highly motivated and ...
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Why don't viruses reach broad concentration outdoors in a city like allergens?

Why don't airborne viruses reach concentrations that infect most people vulnerable outdoors in a city the way an allergen can cause inflammation to everyone sensitive to it. Both are (often) ...
davolfman's user avatar
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Please explain to me the difference of molecular weight in g/mol versus dalton

From my studies i thought so far that: 1 NA * Da = 1 * NA mu = 1 g, However since 2019 SI says that one dalton is only approximately one gram per mol 1 NA Da ≈ 1 g/mol This makes sense if I consider ...
user12256545's user avatar
2 votes
1 answer
175 views

Thermodynamics of passive transport

My question is, where does energy come from for passive translocase's conformational changes? I argue it can't be concentration gradient, as concentration is only statistical phenomenon at micro scale,...
niko papiashvili's user avatar
2 votes
1 answer
111 views

Biomechanics of cells (stress, strain, tension..)

I am confused about the difference between stress, strain, tension, pre-strain and prestress in cells (especially in in-vitro experiments, like cell spreading on a substrate, cell doublets, cell ...
Remember's user avatar
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Contradiction between random molecular collisions and regulated cellular processes [closed]

A cell is a chemical system, consisting of billions of molecules, ions, and atoms. These chemical species are constantly engaged in chemical reactions. Physics gives the impression that chemical ...
seamos's user avatar
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What is the relationship between muscle energy consumption, the period over which the contraction occurs and the mechanical work performed?

I'm asking this question with some basic knowledge of physics and general fitness. Suppose you are lifting a still object with mass $m$ from height $h_1$ to height $h_2$ with an arbitrary (straight or ...
Kinka-Byo's user avatar
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2 answers
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Can tissue flow apart instead of being tightly attached?

Every tissue of our human body consists on cells and cells are not like static "LEGO bricks". They are highly dynamic and can actively move around, due to myosin-actin networks inside the ...
kryomaxim's user avatar
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How to understand the biophysics and math behind a 0.2 second delay between the pulse in my arm and my ankle?

I recently had a test with six blood pressure cuffs; 2 each on arms, ankles and big toes. During the test I could feel the pulses in my arms and legs, and noticed a distinct ~0.2 second delay between ...
uhoh's user avatar
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6 votes
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What does it mean to quantitatively describe a cell?

To begin this question, I will quote Molecular Biology of the Cell (page 38): ... Biological systems are, ..., full of feedback loops, and the behavior of even the simplest of systems with feedback ...
seamos's user avatar
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Is the principle of "the least energy" a fundamental principle of evolution? How does it stand with the rule "the one who replicate the most"? [closed]

The principle of "least energy" seems to be a fundamental law of the universe (is it?). I probably use the wrong word. I'm just talking about the reason why electrons are filling first the ...
JinSnow's user avatar
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1 answer
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Types of structures formed by various types of lipid molecules

Since Phosphatidylcholine (PC) and phosphatidylserine (PS) are roughly cylindrical in shape , they tend to form flat bilayers. Phosphatidylethanolamine (PE) on the other hand is conical in shape which ...
Nikhil Verma's user avatar
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2 answers
224 views

How do physics notions of fluid dynamics relate to pressure gradients in circulation?

I'm having a hard time comprehending why sometimes physiology notions seem to contradict each other and contradict physics teachings. More specifically I don't understand why aortic coarctation causes ...
sha00's user avatar
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20 votes
3 answers
2k views

Why does UV radiation from the Sun cause skin cancer?

What is the specific mechanism makes non-ionizing UVA and UVB radiation carcinogenic? Can lower energy light, like visible light, be carcinogenic because of this mechanism, or is there some kind of ...
ayane_m's user avatar
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Examples for oscillatory behaviour in the human body

I'm looking for examples in the human body which show periodicity, more precisely, I'm looking for examples of oscillating reactions that occur in the human body which can be modelled using the ...
E. Ginzburg's user avatar
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1 answer
192 views

Why do water molecules diffuse along axons direction?

I am studying tractography technique which aims to reconstruct bundles of axons in brain by following the diffusion direction of water. It is very interesting because it is non-invasive. It exploits ...
Manuela's user avatar
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4 votes
1 answer
180 views

Do electric eels produce current as they just move about, and how/why?

https://www.youtube.com/watch?v=y9wktSQdyaE This video demonstrates how an electric eel can supposedly produce up to 800 watts, and power a Christmas tree, which is very topical (a late Merry ...
Johnny's user avatar
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Has anyone tried using functional near-infrared spectropathy to quantitively measure sodium concentrations in the brain?

Functional near-infrared spectropathy "fNIRS", is a biophysics/medical technique that uses the near-infrared part of the electromagnetic spectrum (around 680nm to 810nm in wavelength) to ...
RhinoPak's user avatar
1 vote
1 answer
46 views

The Effects of Large Static Magnetic Fields on the Human Nervous System

How do static magnetic fields impact the nervous system? I imagine with sufficiently intense magnetic fields the Lorentz force is going to change the behavior of nerve impulses, but at what field ...
alessandro's user avatar
-1 votes
1 answer
70 views

What's a cells membrane potential without any leak channels?

Consider the following ion concentrations on either side of a cell membrane (in = inside cell, out = outside cell): $[\text{Na}^+]_{\text{in}} = 10mM$, $[\text{Na}^+]_{\text{out}} = 142mM$, $[\text{K}^...
Jane's user avatar
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4 votes
2 answers
2k views

Why is a solution of cesium chloride used in Meselson & Stahl's DNA replication experiment?

Centrifugation involves separating particles of different sizes, masses, density and etc. In the experiment, the DNA macromolecules are suspended in a solution of cesium chloride gradient and then ...
Bøbby Leung's user avatar
0 votes
1 answer
314 views

Can a hinge joint technically allow rotatory motion?

Let's use a hinge joint and pivot joint as examples. When talking about the difference between them in terms of movements permitted, I see that on any websites and textbooks, the term 'rotation' is ...
Bøbby Leung's user avatar
39 votes
5 answers
9k views

Can bacteria be killed by purely physical trauma?

In a question over on Skeptics Stack Exchange, I half-jokingly listed "blunt force trauma" as a means by which a bacterium could be killed. That makes me wonder if it really is only a joke ...
Robert Columbia's user avatar
2 votes
1 answer
104 views

Question in gel chromatography experiment

Here I am trying to do gel chromatography to separate vitamin B12 and Bovine Serum Albumin (BSA) in this experiment, I am using sephacryl s-100 HR gel column my question is can I use Phosphate ...
HAYA's user avatar
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2 votes
1 answer
48 views

Can viruses be deformed?

Viruses are created in their fully-formed state and do not grow. But one thing has been bugging me lately: can a virus be deformed, e.g. in order to fit into an opening slightly smaller than itself? ...
kaleccrom's user avatar
13 votes
0 answers
186 views

How do the biophysics of how cerebrospinal fluid mechanically protects the brain work?

The two mechanisms I've seen mentioned are the cerebrospinal fluid (CSF) acting as a hydraulic cushion or shock absorber, and how CSF creates a micro-gravity environment through buoyancy. I have very ...
Dahen's user avatar
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1 vote
0 answers
15 views

Can the eye determine which type of defocus is presented to it?

I have a question regarding myopic and hyperopic defocus. My question is, is the eye able to determine which type of defocus is presented to it and if so what mechanisms allow it to distinguish ...
James's user avatar
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1 vote
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How would one model a Neutrophil Extracellular Trap with Hookean Springs?

This is a question based in biology but involves a good amount of physics. Given that a Neutrophil Extracellular Trap (N.E.T) behaves like an aggregate of DNA strands with citrullinated Histones and ...
AandL's user avatar
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1 vote
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Biophysically, how to change from a tonically firing neuron to an occasionally firing one?

In terms of membrane properties, size and neuronal biophysics (assuming no change in incoming excitation), how can a tonically firing neuron become (say during development) an occasionally bursting ...
user7956644's user avatar
1 vote
1 answer
35 views

Question about the Derivation of the cable equation for neurites

I read in Wikipedia how the cable equation was derived (here) and had a specific problem regarding one of its equation: At the start of the derivation it states that we first need to pretend that the ...
Idop11's user avatar
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1 vote
1 answer
181 views

Why the length constant of passive current flow isn't depend on the membrane capacitance?

I read that the equation for the length constant for passive conductance along a neuron depend on the resistance of the plasma membrane, the intracellular axoplasm and the extracellular medium. My ...
Idop11's user avatar
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0 votes
0 answers
32 views

Does the zeta potential of a nanoparticle generally take into account ligand charge?

For example, if I had a quantum dot nanoparticle with conjugated linker peptides capped with polyarginine tracts. Would the localization of negative charge from arginine change the zeta potential ...
Mchiribo's user avatar
2 votes
0 answers
80 views

Why does constant current in electrophoresis mean that the molecule moves at the same rate? [closed]

Two part question: Part 1: I have always learned that when running a SDS-PAGE current is what decideds how fast the macro molecules migrate. However, if the force excerted on a molecule is equal ...
David William Turnell's user avatar
2 votes
0 answers
88 views

What is the charge of (bacterial) ribosome?

Ribosomes are negatively charged and thus electrostaticaly repelled from DNA. However, I could not find a good reference that would allow me to estimate the magnitude of negative charge on a ribosome. ...
Martin's user avatar
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