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Questions tagged [biophysics]

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

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Time span until everything biological is stabilized/finalized after a low-level exposure to ionizing radiation?

Say the x-rays of a common diagnostic CT (< = 10 mSv?). Irrespective of any ultimate effects (linear or threshold detrimental, inconsequential, or even protectively hormetic) just how long until ...
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1answer
35 views

Entropy during neuronal signaling

to begin with: I have some background in cognitive neuroscience, but have not intensely studied the biochemical background of neuronal signalling, so please correct me if my basic understanding is ...
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1answer
83 views

Is there any independent non-DNA based information system in the cell

The information in protein is not neccessarily independent of the genome as the information of amino-acid sequence comes directly from the genome. The process of post-translational modification may ...
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1answer
123 views

Difference between prions and amyloid proteins?

Amyloid and prions are misfolded proteins, but what, if any, is the difference between them? Is amyloid a type of prion with a fibrillar structure?
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37 views

How to derive the deactivation time constant in this model of Acetylcholine Receptor state kinetics?

I came across this simple analytical expression of time constant of deactivation in Elenes et al., 2006. How does one derive this expression $$\displaystyle\tau_\text{deactivation}\approx\frac{1}{D_+ ...
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1answer
75 views

Why is there a layer of moist lining the inner walls of alveoli?

I'm taught that the walls of the alveoli are moist, so gaseous oxygen molecules can dissolve into this water. This then allows the dissolved oxygen (liquid state) to diffuse faster from the alveoli ...
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1answer
29 views

Why does the DSC peak have a bell shape?

I am studying Differential Scanning Calorimetry (DSC) and am not quite understanding why most proteins have a bell shape when the heat capacity is plotted against the temperature. Also, I would ...
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2answers
87 views

Why biologic systems tends to become more complex?

From elements, chemical compounds, cells, multicellular organisms, society evolves and with each step possibilities increase and things get complex. We are builing structures like ribosome builds ...
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2answers
52 views

Effects of horizontal vs. vertical motion on human body

I want to know if moving along a vertical plane in a circle differs in its effects on the human body from moving horizontally in a circle. Imagine a ferris wheel with a diameter of 50 metres. If a ...
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2answers
148 views

Why do neurons have long axons but short dendrites?

Cian O'Donnell, a British neuroscientist, originally asked this question on Twitter: https://twitter.com/cian_neuro/status/1075432086692089857. I am not a biophysicist by training but I wonder whether ...
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2answers
119 views

Can light function as a neurotransmitter?

Any animal with an eye has photoreceptors, which are essentially light-sensitive neurons. Green algae have channelrhodopsin, which are ion channels that open and close in response to light. Clearly, ...
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1answer
96 views

What is meant with “the chest wall and lungs are coupled together”?

Since the lung and chest are elastic, we can represent them with springs. Under normal conditions, they are coupled together: the “lung” springs are stretched and the “chest” springs are compressed. ...
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1answer
44 views

How are sound waves amplified while traveling within the cochlea?

How are sound waves amplified while traveling from the basal membrane to apical membrane within the cochlea? Are they amplified by the movement of the stapes?
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1answer
33 views

What is (are) the medium of conduction for an electrical current with an external source in the human body?

I am trying to get some background for some personal research I am doing into the effects of Electro Convulsive Therapy. I don't understand how electric current from an external household source, say, ...
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0answers
18 views

Electrical mobility of biological relevant ions in solution

I've been trying to find references of electrical mobility of ions relevant in neuroscience (K+, Cl- Ca2+, HEPES). This is important to calculate liquid junction potentials of electrophysiology ...
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0answers
58 views

What waste products do cells secrete in culture, and at what rate?

I am designing microfluidic chips for mammalian cell culture. One aspect I am interested in modeling is the rate at which I must renew media to ensure that: Cells receive enough nutrients Cytotoxic ...
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1answer
315 views

Can multiple antibodies bind the same antigen?

Given the size difference between small molecule antigens and antibodies is it ever possible for multiple antibodies to bind to the same antigen if they recognize different domains on that antigen? ...
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1answer
29 views

Square-cubed law and health

Does the square-cubed law lead to possible health detriments for taller people? I'm not sure what the optimum height is for humans (e.g. due to their cross-sectional bone density constraints), but ...
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1answer
26 views

Is it possible to induce protein activation via frequency-specific mechanical waves? [closed]

Would it be possible to induce shape changes in specific proteins by providing specific frequencies of mechanical waves in a thermostatically controlled environment such that those proteins may be ...
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0answers
60 views

How can diving with 100% oxygen not destroy your lungs? [closed]

It is possible this should be moved to physics, depending on the nature of the answer (i.e. if the reason is physical). But I suspect the explanation is biological, so I posted it here. Sometimes ...
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1answer
68 views

Fraction of channels open at equilibrium

I found the formula for the fraction of channels open at equilibrium for a three-state mechanism (Colquhoun's paper in the microelectrode book http://www.utdallas.edu/~tres/microelectrode/me.html) k1 ...
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2answers
83 views

Are resonances the reason receptors work?

From Visual phototransduction - Wikipedia: When struck by a photon, 11-cis retinal undergoes photoisomerization to all-trans retinal which changes the conformation of the opsin GPCR leading to ...
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1answer
37 views

Is summation linear in a passive membrane?

I am not too sure what it means for summation to be linear? I am running a simulation and as I decrease time for the second EPSP the amplitude decreases. Does summation being linear mean that there is ...
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1answer
595 views

Why does UVA penetrate deeper than UVB, though it's weaker?

Even though UVA radiation ranges in longer wavelengths (315–400 nm) than UVB (280–315 nm) and thus is less energetic, UVA is able to penetrate deeper into the skin and even reach the dermis. Why is ...
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43 views

effect of arterial vasocontriction on the pressure in arteries

if experimentally one induces smooth muscle contraction on an artery and cause it to constrict, keeping the cardiac output same and also the arteriolar resistance(total peripheral resistance) the same ...
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0answers
125 views

What is the biological relevance of RIPPLE phase in membranes?

I was reading about ripple phase in bilayer lipid membranes which is described here as a meta-stable state between lamellar tilted crystalline and lamellar fluid state. It is also known that ripple ...
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1answer
74 views

Causes of the stochastic behaviour of voltage-gated ion channels

I came up with the following electro-mechanical model of a voltage-gated ion channel, resp. of its voltage sensor as described here and here. The voltage sensor is a bistable system with two local ...
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0answers
87 views

law of laplace and pressure developed in arteries

in arterioles the pressure depends on the impedance of the vessel(elasticity and youngs modulus) cardiac output pre arteriolar resistance what i want to ask is will the pressure also depend on law of ...
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0answers
35 views

Calcium and nitric oxide: does a numerical relationship exist?

Currently, I am trying to understand how nitric oxide and calcium are related during the production of the former (I am not a biologist nor a chemist, so my knowledge about these topics is very poor). ...
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1answer
465 views

How can some residues in the active site of enzymes be protonated with a pKa < 7?

It is reported in many papers, that some residues in the active site of enzymes need to be protonated to get functional enzyme, where these residues have a low pKa (for let us say 5). How can that ...
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0answers
34 views

Validity of Acoustic Weapon Effects on Biological Organisms?

There is alot of rather contradictory information present on the biological effects of acoustic weapons with a bevy of scientific articles claiming that they cause harm to biological organisms with ...
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1answer
135 views

What is the point in the Neuromuscular Junction?

Surely a direct connection (i.e. an electrical synapse) between motor neurone and the sarcolemma would allow for much faster neuromuscular transmission? It is my understanding that chemical synapses ...
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0answers
47 views

Are trees still carrying their leaves more likely to be felled by an autumn storm?

Is there evidence that trees still carrying their leaves are more likely to be felled by an autumn storm than trees already having lost their leaves? At first sight this seems plausible (and might be ...
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1answer
251 views

How interrelated are computational biology and biophysics? [closed]

I am considering applying to Ph.D. programs, and am not sure what direction to take. I'm hoping you all can help me out. I have a background in both biology (molecular focus) and physics (condensed ...
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1answer
63 views

Calcium concentration in activated dendritic spines?

What are the typical calcium levels reached in single postsynaptic spines following activation of NMDA receptors by an EPSP or backpropagating spike? Everyone seems to refer to that one Neuron paper (...
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1answer
136 views

Mathematical relationship between membrane conductance and conduction velocity?

By what factor would the myelin need to decrease membrane conductance (gm) if you wanted conduction velocity in a 10 μm myelinated mouse axon to be 100 times faster than in a 10 μm unmyelinated mouse ...
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2answers
211 views

What are the structural factors affect enzyme's Km?

Is there any rules (should not be exact), to estimate the kinetic changes in an enzyme if I did any mutation on it? If I cannot estimate the new kinetic values, is it possible at least to clarify or ...
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2answers
52 views

Does opening of ion channels alter the membrane potential directly?

Does the opening of a voltage-gated ion channel (i.e. the change of configuration of the protein) by an appropriate local change of the membrane potential directly and significantly alter the membrane ...
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1answer
53 views

How are fMRI responses to auditory stimuli measured?

How can fMRI experiments be conducted which measure the response to auditory stimuli (e.g. music) when the apparatus makes such loud, nasty, and distracting noises? Are there quieter MRI tomographs in ...
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1answer
129 views

Half-life and production rate of ion channels

There are "not millions, not a few hundred...somewhere in between (some tens of thousands)" of ion channels in a neuron. Given the number of ion channels per neuron, knowing the half-life of ion ...
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1answer
33 views

Measuring depolarizations over the membrane

Measuring the rest potential of a membrane is relatively easy and straight forward: put one electrode inside the neuron, the other one (the "counter electrode") outside the neuron. Because ...
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1answer
40 views

Are ion channels/resistancies in Rall's model voltage-independent or not?

In the description of the electrical circuit that models a piece of membrane in Rall's Scholarpedia article on Ralls model, I read: "[...] this conductance [$G_e$] is zero under resting ...
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1answer
437 views

Can a mathematical function be assigned to ECG diagram?

This is a 12 lead electeocardiogram of a 26 year old male: This is the graph of function $5sin(7x)sin(.5x)cos(3.25x)$ This graph look quite similar to the ECG diagram.After sketching this graph, I ...
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1answer
96 views

What would EEG recordings reveal if their resolution was better?

1. Temporal resolution Of course, we would see higher frequencies. But would these be informative? Aren't the frequencies measured today near the border to noise? 2. Spatial resolution I guess LFP ...
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1answer
199 views

Speed of passive transport of ions in the dendrite

I tried hard to get them, but I didn't get any numbers. My (subjectively) best Google search was for "speed propagation post-synaptic potential". My question is: How fast are ions transported ...
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3answers
163 views

What is measured by electroencephalograms and local field potentials?

In the Scholarpedia article on local field potentials (2013), I read: The current view is that EEG and LFPs are generated by synchronized synaptic currents arising on cortical neurons, possibly ...
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1answer
90 views

white blood cells and cancer cells transport through lymphatic vessels

It is a well-known fact that both of these cells can reach the lymphatic vessels from interstitial space. How does it do so physically? Are there any mathematical models describing this process? It ...
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0answers
163 views

Protein phosphorylation in the cytoplasm. Typical time scale?

Is there a typical protein phosphorylation rate in the cell cytoplasm under physiological conditions, or at least an upper-bound? Suppose a protein $A$ is being phosphorylated into $A^*$ with the ...
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4answers
363 views

Are there known life forms that are able to transform mechanical energy into chemical energy?

Are there known life forms that are able to transform mechanical energy into chemical energy? This question asks a similar subject, but more specific and has no answers. The background of this ...
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What structures (i.e. organs) are suspended by tensile forces?

In several areas of biomechanical literature I have read, the concept of "tensegrity" has arisen. Definitions are as follows: “The integrity of a stable structure balanced by continuous structural ...