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

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628 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. ...
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0answers
21 views

Meaning of 'forms of free energy'?

I was doing a practice exam paper and it asked for different 'forms of free energy'. I am a physicist rather then a biologist so 'free energy' to me means Gibb's Free Energy: $$G=H-TS$$ But I cannot ...
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18 views

Is it possible to biologically convert potential energy to chemical energy?

To lift an object x meters it is necessary to expend, at a minimum, an amount of energy corresponding to the increase in that objects potential energy associated with the increase in height. When ...
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8 views

Do a patient's cells have a higher or lower resistance to hemolysis?

There is this answered question in my book, but I don't understand the solution. A sick patient's blood cells have hemolysis in a NaCl solution 5g/l and in normal people blood cells hemolysis happens ...
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0answers
8 views

Interaction study of oligomeric proteins

I'm dealing with two different protein(say, protein_a and protein_b) which stays in an interacting-oligomeric form in biological system. I have so far successfully been able to purify both the ...
2
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0answers
20 views

Photosynthetic efficiency and light harvesting efficiency

Is there some sort of measure of the light harvesting efficiency (possibly like transfer time) that is directly related to the photosynthetic efficiency in some sort of equation? Also, how important ...
2
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1answer
39 views

Can geckos climb a wet surface?

We know geckos can climb vertically or even upside down a surface like glass. But can they do that on wet glass?
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2answers
50 views

Bernoulli’s Principle in the Cardiovascular System

Below are graphs which illustrate the cross-sectional area, velocity, and fluid pressure through each vascular segment of the cardiovascular system. It makes sense that velocity and cross-sectional ...
4
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1answer
102 views

What determines whether an action potential is inhibitory or excitatory?

What determines whether an action potential is inhibitory or excitatory? Is it determined by the receptors, the neurotransmitters, or some other mechanism?
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30 views

How spermaceti makes a whale float

In the biochemistry book I'm reading (Box 10-1, Lehninger Principles of Biochemistry), an example is given in whales of how spermaceti (a wax located in the whale head), when at sea level is a liquid, ...
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3answers
661 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 ...
3
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1answer
45 views

If the average resting potential of a neuron is -70 mV, why is there such a high ratio of potassium ions inside relative to out?

My bio teacher was discussing the ratios of different ions inside versus outside the cell. $$\text{OUT:IN}$$ $$\text{K}^+ (1:20)$$ $$\text{Cl}^- (11.5:1)$$ $$\text{Ca}^{2+} (10000:1)$$ ...
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1answer
34 views

Can Nanodiscs be used to study membrane energetics?

Nanodiscs have changed they way we can study the structures, insertion, and functions of transmembrane proteins. Below is an image of a nanodisc bilayer. The key difference, as far as I can tell, ...
4
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1answer
28 views

Which hydrophobicity scales are best for detecting transmembrane regions, and why?

There are many hydrophobicity scales for protein analysis. Broadly, I gather the differences between them are from the experimental method to acquire the data and the normalisation (or lack thereof) ...
2
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1answer
65 views

Has anyone modelled calcium oscillations using Matlab software? [closed]

I have been trying to model calcium oscillations using MatLab, but I cannot obtain the oscillation. I created a function where I put all the equations and used ode15s to call the function. I have ...
8
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2answers
138 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?
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0answers
77 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 ...
2
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1answer
83 views

What biological processes can affect the temperature of the shadow a tree casts?

Assuming two trees have similar shape and leaf coverage, could differences in the biological processes among them lead to differences in the temperature of the shadow they cast? What biological ...
10
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1answer
1k views

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 ...
3
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2answers
52 views

Why do negative ions flow into a cell in an inhibitory synapse, even though a neuron has a negative resting potential?

In my spare time I have been reading an introductory Psychology textbook and this question came to my mind after reading about action potentials. I have no previous knowledge in chemistry so if I do ...
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0answers
22 views

Book-recommendation: plant biophysics [closed]

I'm a physicist by training am looking to learn more about the biophysics of plants. Can you give me your recommendation of good resources on plant biophysics? Books are preferred.
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3answers
258 views

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 ...
3
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1answer
95 views

Explanation of ECG in MI using an electrostatic model

I found a paper presenting an electrostatic model to explain the ECG recorded in various leads. This model essentially calls for considering the depolarization wavefront to be the major contributing ...
4
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1answer
39 views

How does loss of the electrochemical gradient result in heat production?

As far as I understand, uncoupling of the flow of protons and ATP-synthase provides a bypass for protons between the outer and the inner membrane of mitochondria so that the protons don't have to go ...
4
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1answer
30 views

Wearing sunglasses during a solar eclipse [closed]

Note: I had asked this on Physics, but it is off-topic there due to being about safety. On the BBC's guide to eclipse-watching, Dr Lucie Green says: Watching an eclipse with normal sunglasses ...
2
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0answers
37 views

Infrared emitting diode eye safety

I'm thinking of creating my own laser tag system and am a bit concerned about the eye safety aspect. Most of the homebrew system I've seen use the TSAL 6100 ...
4
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2answers
76 views

Mechanism behind negative conductance of ion channels

I am struggling to understand negative conductance shown on I-V curves on ion channels. Mechanistically, negative conductance means that inward (or outward) current increases when voltage across ...
3
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2answers
59 views

How to conceptualize the action potential?

In my AP Biology class, we were taught that action potentials are not electrical impulses in the same way current travels through a wire. Rather, we were taught that action potentials are changing ...
4
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2answers
114 views

Proteins that give color (without fluorescence)

Is there proteins that have strong color, that could be seen without the need of UV and with naked eyes (with white light) - in mammalian cells? Searching for reporter, something like GFP, but that ...
3
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2answers
56 views

Determining how much energy a plant takes in?

I asked a question on WorldBuilding.SE, "Are diamond berries possible?". This led to asking a question on Chemistry.SE about the amount of energy required to burn a 1 ct. diamond (−6.527kJ). The ...
7
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1answer
197 views

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 ...
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0answers
23 views

What are some commonalities between biology systems and semiconductor physics?

It seems that fundamentally both neural system and semiconductors are operating using similar principles on the same scale. Things such as drift and diffusion current plays major role in both systems. ...
7
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1answer
265 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
41 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
37 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
59 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 ...
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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
42 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
129 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
198 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
40 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 ...
3
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1answer
52 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 ...
7
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1answer
86 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 ...
5
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1answer
292 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 ...
4
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1answer
74 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
169 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?
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2answers
509 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 ...
14
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1answer
238 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 ...
12
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1answer
286 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 ...
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1answer
89 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 ...