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

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1answer
211 views

Why does the membrane of a neuron not stay at its depolarized state?

When an action potential is transmitted along the axon, the membrane reaches its depolarized state by opening Na+ channels. Both K+ (potassium) and Na+ (sodium) are now on both sides with close to ...
2
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1answer
28 views

What governs the distribution of blood vessels?

Whenever someone is sick, doctor places 2 fingers on wrist & observes the heart-beat-rate by feeling pulses of a certain artery. To me it seems the distribution of blood vessels are pretty ...
3
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1answer
33 views

What is the statistical relationship between radioactivity and mutation rate?

This question tries to narrow down the scope of that question. What is the statistical relationship between radioactivity and mutation rate? By how much would the mutation rate be lowered in a ...
2
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1answer
31 views

What does these $\Delta \Delta G$ numbers signify?

I was reading a paper and came across this table showing $ \Delta \Delta G$ numbers of different nucleotide sequences in DNA/RNA. I know that $\Delta G$ is free energy and $ \Delta \Delta G$ is ...
14
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2answers
1k views

How do birds deal with their eyes drying out at high speeds?

My eyes tear up when cycling at 15 mph, which is nothing compared to bird airspeeds. Do birds continuously produce lots of tears and blink a lot, or do the eyes self-moisturize from the inside ...
5
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1answer
36 views

Stretching and compressing bones

The Young's modulus of elasticity when a bone is stretched is : 16×109 and when it is compressed, it is 9×109 N/m2. That means, change in length will be more if you compress a bone as compared to ...
6
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1answer
84 views

Why do most organisms have negative supercoiled DNA?

It has been observed that in nature most organisms have negative supercoiled DNA and that few organisms have positive supercoiled DNA. Some of the organisms that have the positive supercoiled DNA live ...
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0answers
25 views

How can the directionality of a protein structure be defined?

For a DNA molecule, you can define directionality using the convention of a 5'-3' direction on the Sense strand. However, using an N to C convention for a protein doesn't work since the ends may be on ...
2
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0answers
35 views

How to get a pdb file of a single atom?

I am trying to get a pdb file that contains a single atom, it doesn't matter if it's Hydrogen or another atom. How can I obtain this? Are there any pdb files with just a single atom available to ...
2
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1answer
44 views

Is there any knowledge of physics can be applied in to evolution?

I have asked a similar question in Biology.SE (What physics knowledge can be applied to biology of organisms and ecosystems?), but it just about organisms and ecosystems, not evolution. After watching ...
5
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1answer
195 views

What physics knowledge can be applied to biology of organisms and ecosystems?

In the wiki page of Biophysics: Biophysics spans all scales of biological organization, from the molecular scale to whole organisms and ecosystems. But after searching on the internet; the ...
3
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0answers
53 views

Criteria for compound action potential thresholds

As opposed to action potential thresholds (which are binary yes/no events), electrophysiological thresholds of compound action potentials are arbitrary. Mostly a certain noise level is picked and when ...
5
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2answers
125 views

How do diving marine mammals avoid decompression sickness?

How do marine mammals, whose very survival depends on regular diving, manage to avoid decompression sickness or "the bends?" Do they, indeed, avoid it?
6
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2answers
288 views

How do marine mammals control buoyancy?

Presumably, as a whale or seal dives, its lungs get compressed by the increasing water pressure, and it gets less buoyant. Under this model, for a given amount of air taken in at the surface, the ...
13
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1answer
193 views

Effect of pupil responses on the electroretinogram

The electroretinogram (ERG) is generally considered to reflect the retinal processing of a light stimulus, typically a photoreceptor response followed by secondary neuronal activity. I am wondering ...
11
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1answer
223 views

How fast can a human run?

I'm a runner (cross country) and I'm always amazed at how fast Olympic sprinters are. There's a lot of hype about those in the 100-meter dash being the fastest in the world, and we're constantly ...
0
votes
1answer
73 views

How non-invasive blood glucose concentration measurement work?

Diabetes patients need to conduct the “fingerstick” a few times a day. One of the mechanisms of "fingerstick" is to take small amount of blood sample and put it onto a test strip. The enzyme on the ...
1
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1answer
46 views

How non-invasive blood glucose concentration measurement work? [duplicate]

Diabetes patients need to conduct the “fingerstick” a few times a day. One of the mechanisms of "fingerstick" is to take small amount of blood sample and put it onto a test strip. The enzyme on the ...
2
votes
1answer
278 views

What is the difference between rheobase and threshold?

Neuronal tissues can be excited by electrical stimulation. Two commonly encountered characteristics for electrically stimulating nerve cells is the threshold and the rheobase. My question is what the ...
5
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2answers
109 views

Problems understanding membrane potential

I understand that membrane potential is the difference of the extracellular and intracellular ionic charges, due to their concentrations. We say that the extracellular space has a charge of 0 and then ...
6
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4answers
300 views

Is human vision sensitive to frequency or wavelength?

In a vacuum, there is a one-to-one correspondence between light frequency ($\nu$) and wavelength ($\lambda$), ie. $\lambda=c/\nu$. But in a refractive medium, $\lambda=v/\nu$, so while the frequency ...
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0answers
38 views

Unexpected stoichiometry n in ITC experiments

I'm looking at the binding of a small molecule to several RNA constructs and tried to determine the binding constants. To do this I've performed a few ITC experiments on this system, the results were ...
7
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2answers
153 views

Can a single axon propagate multiple simultaneous action potentials?

I have not been able to locate any research that indicates whether a single axon of a neuron or nerve cell can conduct multiple simultaneous (i.e. spatially separate) action potentials. I am aware ...
4
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1answer
130 views

How efficient is the human body at metabolizing food?

My friend and I were having a discussion over how "efficient" human digestion is. If a human ate a 1000 calorie hamburger, how many of those calories (how much energy) does the body process into ...
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1answer
57 views

How to measure the total number of cells in an average human body?

I have got one assignment to calculate the approximate sum total of all cells in the human body. How to tackle this problem? I know that the current statistics is $10^{13}$ cells. I wanted some hints. ...
1
vote
1answer
89 views

How to estimate the DNA density in human sperm head? [closed]

I have got an estimate of sperm head volume from internet.Like consider it as a disk of order 4-5µm. Now I wanted to find the DNA density in the sperm head. How to find that?
2
votes
1answer
35 views

What is the biding site code recognized by the parts of the spliceosome

Another question about another Youtube video. At 0:50, the splicing process begins to remove the non-coding section of the DNA (intron), so the different parts of the spliceosome attach to the borders ...
6
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1answer
57 views

What regulates the timing of the motion of molecular machines during DNA Replication?

This question is about this video I found on Youtube. I just want to know what is the mechanism which regulates the timing of motion of the parts of these molecular machines. I know that those big ...
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1answer
53 views

How Ants know about Earthquake?

How does an ant know about Earthquake is it because of an organ or due to other factors?
2
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1answer
40 views

Kinesin-5 / cytoplasmic dynein spatial density distribution in neurons

Is there some way to experimentally determine the density distribution of Kinesin and Dynein in a Neuron? Fluorescence labeling would be impossible(?) as GFP markers would probably alter the motor ...
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2answers
52 views

Useful physical information of a protein

Beside energy and heat, I don't know any useful physical information of a protein. Can you help me list some of it. Somethings like Fourier-transform infrared spectroscopy to provide protein structure ...
2
votes
1answer
35 views

Muscle force/energy relationship

I found the Hill muscle model, which helps relate the force a muscle can generate to its change in length over time (its "contraction velocity"). Is there a similar model to get an idea of the energy ...
3
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2answers
89 views

How to determine whether the energy of a stem-loop fold is significant or not?

If I have a predicted RNA stem-loop of energy -0.30 kcal/mol, and another of -4.9 kcal/mol, how do I tell whether such a structure is a significantly stable structure or not? Our two competing ...
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2answers
61 views

Which types of hydrogen bonds are known to exist in RNA secondary structures?

I'm programming an implementation of an algorithm for pattern matching in RNA structures. The algorithm assumes the following types of base pairs: Plain: No base pairs (just the primary structure of ...
2
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1answer
36 views

Protein Conformation Modeling

I'm interested in learning about computational modeling in biophysics. I have heard some amount about people modeling proteins as a network of ideal springs to examine things like conformation ...
1
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1answer
27 views

Nervous System : Signal Translation

If a device were created to monitor the nervous signals from the heart, including stable heartbeats, rapid heartbeats, etc., and this device were capable of transmitting the "stable heartbeat" to the ...
2
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1answer
41 views

What's the best way to measure/calculate the size of a light beam at the sample of a microscope?

I am using a microscope with an LED derived light through the epi-fluorescent port of a microscope. I know that the "field of view" for a given objective is equal to the field number/magnification ...
4
votes
1answer
57 views

Do local field potentials (LFP) create waves on the surfaces of nerve cells?

Are waves created by the LFP on the surfaces of neurons cell bodies? Since the cells have a resting potential, do these waves create harmonic oscillation of the membranes at particular frequencies? ...
4
votes
2answers
419 views

How is membrane capacitance related to the increased speed of saltatory conduction?

Here is the original question which inspired my question. As explained by the answers there, the reason saltatory conduction in myelinated neurons is faster than non-myelinated conduction is because ...
9
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4answers
2k views

How do trees lift water higher than 10 meters?

The atmosphere pressure is 10 meters of water (approx). This means that it is impossible to lift water higher than 10 meters with vacuum or сapillary action (on Earth, under normal conditions). There ...
4
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1answer
3k views

Isotropy of sarcomere bands in skeletal muscle cells

As seen under a polarization microscope, the A-Band in skeletal muscle fibres is so named because it is anisotropic in its refractive index which is a characteristic of orderly crystalline structure. ...
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0answers
25 views

How is saltatory conduction faster than conduction of unmyelinated fibers? [duplicate]

It's always the same explanation that currents are able to "hop" along Ranvier nodes instead of passing continuously along the axon making saltatory conduction more efficient than continuous ...
1
vote
1answer
65 views

What is the strength of human cornea?

What is the difference of pressure a human eyeball cornea (cornea, lens and other elements separating vitreous body from air) can handle? Or asking differently: what the outside pressure should be to ...
9
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2answers
461 views

How do small animals make loud sounds?

Walking past the park today, I heard a cicada so loud I thought at first it must be some sort of large power tool. How is it that that very small animals like cicadas (crickets, etc.) can make such ...
3
votes
1answer
83 views

Do voltage-gated calcium channels affect neuronal conduction speeds?

We have a hypothesis that a drug may block the voltage-gated calcium channels (VGCC) in annelid worms. We are wondering whether there are any correlations between VGCCs and neuron conduction ...
3
votes
1answer
1k views

What is the exact principle of capillary isotachophoresis?

I know it's a type of capillary electrophoresis, but I don't get how does the separation happen exactly.
2
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1answer
550 views

What is the relationship between UV wavelength and penetration depth into human skin?

Some background - Some recent research has strongly suggested that UVA penetration into the skin is far more dangerous than UVB, a very good example is this paper by Agar et al. (2004). My query is, ...
9
votes
2answers
3k views

Why is saltatory conduction faster than continuous conduction?

How does spacing apart sodium and potassium channels allow the action potential to travel faster down the axon? This is the reason always cited for saltatory conduction and myelination, but my mental ...
7
votes
4answers
421 views

Does darker skin color make it easier to live under sun?

I have always thought darker colors absorb more heat from the sun, so if you are wearing a white T-shirt you will be cooler under sun than wearing a darker T-shirt, or a black piece of steel will be ...
1
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1answer
176 views

What is the energy balance of cooking?

If I cook some food, I get apparently several energetic advantages: thermal : the temperature of the food is closer or superior to the temperature of my body or internal organs, so I do not have to ...