Questions tagged [biophysics]

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

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29
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2answers
1k views

What are the trajectories of flying insects?

Many flying insects tend to have very jagged trajectories. For moves of a fruit fly looks like a random walk. Is there any research on the properties of trajectories (e.g. their fractal dimension or ...
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3answers
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How, on a physical level, does ATP confer energy?

When ATP is used as the energy currency to make, say, reaction X + Y → Z happen, is what happens on a physical level down at the molecular scale that during the reaction ATP + H2O → ADP + Pi  &...
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3answers
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Why is saltatory conduction in myelinated axons faster than continuous conduction in unmyelinated axons?

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 ...
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2answers
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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 ...
18
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1answer
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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 ...
17
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4answers
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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 ...
17
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1answer
613 views

Quantum mechanics in biology

There is a growing interest in the applications of non-equilibrium quantum dynamics to describe biological processes (I'm not talking here about Penrose's old theories, but new stuff -- quantum ...
16
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3answers
2k views

Why don't our cells merge when their phospholipid membranes touch each other?

Membranes of our cells consist of lipid bilayer (with some other components mixed in). Why wouldn't those lipid bilayers glue to each other and make the cells merge? If you suppose that it's due to ...
16
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2answers
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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 ...
16
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1answer
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Why doesn't the cell membrane just…break apart?

Forgive me if this is a silly question. I can't understand the basics. Why doesn't the cell membrane just break apart? What's keeping the layers in the phospholipid bilayer together? I know that the ...
15
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3answers
1k views

Is the amount of the soil reduced when plants grow?

According to the principle of mass conservation I think the amount of the soil should be reduced when plants grow. But this reduction is not typically observed. For example, some trees (big trees) ...
15
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2answers
2k views

Can UV radiation be safe for the skin?

It is well known that UV radiation can damage the DNA and generally harm our skin. We also know that UV radiation helps on the production of melanin and Vitamin D. From what I could find, the DNA ...
15
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1answer
559 views

Effect of pupil responses on the electroretinogram

The electroretinogram (ERG) is a measure of electrical activity of the retina. It is typically recorded from the cornea with a wire electrode or gold-foil electrode. Generally, the the ERG is ...
14
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2answers
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Is the EC50 of an activating protein for an enzyme a good indicator for the binding affinity Kd?

We work with a membrane protein system where measuring the affinity between the enzyme and the upstream activating protein has been difficult, and when measured in detergent solution, it is almost 100 ...
12
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5answers
22k 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 ...
11
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1answer
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What is the mass of a pigeon tail feather?

There is question at Space.SE If I drop a feather from orbit, would it burn up or “hit” the ground? there is an attempt to answer the question, but the mass of pigeon tail feather and possibly the ...
11
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2answers
739 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?
11
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1answer
4k views

What is the transmembrane 'Positive-Inside Rule' nowadays? Has the definition changed over time?

First definition. Two publications by von Heijne in 1989 and 1992 coined the 'Positive-Inside rule' and showed it's practical value in topology prediction of transmembrane helices. It was clearly ...
10
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2answers
13k views

Why are potassium channels slower than sodium channels?

I am relatively new in the subject of biology. I have a strong mathematical background and in order to get into the field of computational neuroscience, I am trying to get some biological background. ...
10
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1answer
338 views

Why don't dragonflies wings collapse?

How do dragonflies manage to fly at such high speeds without their wings collapsing? Their wings are thinner than paper, but they do not even flutter. What gives them their strength?
10
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2answers
550 views

Can a living organism run on electricity?

Each time I'm too lazy too cook I think it'd be cool to be able to just plug myselt into an outlet. Yet I know it is not possible - I need amino acids and a lot of other stuff that electricity can't ...
10
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1answer
2k views

What is the difference between organelle membranes?

Cells and organelles are contained in lipid bilayers. I'm particularly interested in eukaryotic organelle bilayers and the biophysicochemical differences between them. Many papers assume a ...
10
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2answers
188 views

Is there a biophysical causation from local field potential (LFP) to spikes?

Many experiments showed that neurons tend to fire at some phase (usually trough) of local field potential (LFP) oscillations, such as theta or gamma rhythm. LFP is supposedly generated by a population ...
9
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2answers
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What is the anatomical term for a two jointed leg?

Allow me to apologize in advance for the layman's terminology. I'm wondering what the anatomical term for a cat- or a goat-style hind leg is. Cats, goats, t-rexes, and many many other animals don't ...
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3answers
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Why don't phospholipid bilayers dissolve?

I just started learning about the structure and composition of cell's membrane and there is something that I fail to understand. The membrane is composed of a phospholipid bilayer. The phospholipid ...
9
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1answer
6k views

Why human cannot stand still in one place?

When a human stands in one place, he cannot stand still but we can see the body slightly swings. Is this due to the Earth rotation or it has something with biology and muscles relaxations? I have ...
9
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4answers
409 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 ...
9
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1answer
609 views

How does membrane potential vary between intraceullar membranes and the cellular membrane?

Question Does each type of membrane have a different membrane potential? I'm especially interested in answers that can cite academic papers that have attempted to measure membrane potentials. ...
9
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2answers
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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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2answers
5k 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 ...
9
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1answer
2k views

What keeps the resting potential of neurons constant at -70 mV?

I know the sodium-potassium pump pumps out 3 Na+ ions and pumps in 2 K+ ions per reaction so the negative charge in the axon increases. However, once the voltage (difference of charge inside and ...
8
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3answers
3k views

Why don't membrane proteins move?

I understand that based on their tertiary structure, intrinsic proteins have hydrophobic non-polar R-groups on their surface and that they 'interact with the hydrophobic core of the cell membrane to ...
8
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3answers
375 views

Is Einstein's mass energy equivalence ($E=mc^2$) relevant to biological systems?

I'm more than 100% sure that the kilograms I eat don't get directly converted to feces and urine. I'm sure some of it goes to regenerating tissue that is constantly being disposed as well, and maybe ...
8
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1answer
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What physical evidence exists that shows motor proteins “walking” within a cell?

Various animations on the internet show the motor protein kinesin walking within a cell. Is this an approximation? How does this happen and (based upon what physical evidence) how do we know it "walks"...
8
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2answers
349 views

Is “exhaustion” of the Hodgkin-Huxley membrane at constant stimulation a real phenomenon?

I was playing around with a simulation of the Hodgkin-Huxley model using their original parameters for the squid giant axon. By applying a constant stimulation current to the model in resting state, ...
8
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2answers
1k views

Which part of human body sustains most pressure when standing up straight?

Let's suppose a healthy fit barefoot young adult standing comfortably on a flat solid surface. A reasonable guess is somewhere around the foot. But is it the ankle, the heel, or the Metatarsus?
8
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1answer
231 views

Can any organisms see non-electromagnetic radiation?

Some examples would be cosmic rays, neutron radiation, alpha radiation, beta radiation, muon radiation, and antimatter radiation. Some related questions: How is non-electromagnetic radiation detected,...
8
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1answer
178 views

PDB Mining: Why Do I Find Atoms Less than 1 Angstrom Apart?

I am attempting to find potential Hydrogen bonds between Hydrogen donors and aromatic ring acceptors. I do this by predicting the location of Hydrogens on residues and then calculating how far these ...
8
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1answer
492 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?
8
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2answers
2k 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 ...
8
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2answers
9k 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 ...
7
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4answers
2k 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 ...
7
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1answer
1k 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 ...
7
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3answers
14k views

How do warm-blooded animals keep their temperatures constant?

Warm blooded animals like us keep their temperature constant irrespective of their surroundings. But how do they do that? Energy should be supplied from the inside. I assume that reactions like making ...
7
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1answer
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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 ...
7
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1answer
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What is the reason behind high resting membrane potential of pacemaker cells?

Pacemaker cells have high resting membrane potentials of -50 to -40 mV, whereas normal cells have their resting membrane potential around -70 mV. Which ions, and what kind of channels are responsible ...
7
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2answers
997 views

Permeability of Plasma Membrane

I’m having trouble grasping why small polar molecules can cross the hydrophobic region of the membrane and not ions. Won’t the polar molecules be attracted to the watery extracellular medium and not ...
7
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1answer
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Why lipophilic molecules can pass phospholipid bilayer, in spite of 2 hydrophilic layers?

It is commonly told that, hydrophobic/ lipophilic/ nonpolar molecules can quite easily pass phospholipid bilayer, and hydrophilic (polar or ionic) molecules can't pass (when no protein aid that); ...
7
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2answers
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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 ...
7
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1answer
638 views

Double stranded nucleic acids are more 'durable' than single stranded nucleic acids?

I'm struggling with a question I've been asked. "Why is double stranded genetic material more 'durable' than single stranded one?" I know that double stranded genetic material is more stable due to ...

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