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22

Dickinson (2005) has a good review of insect flight, including behavior, biomechanics, electrophysiology, and neural control with links to more of the primary literature. What follows is a general summary thereof. The jagged trajectories you mention are called saccades in the insect flight literature. In Drosophila, saccades are ~90° turns accomplished in ...


18

Usually in biology (and being ATP, it most probably is biology), it's one of two things. The gamma-phosphate (the third one, the one farthest from the adenosine) is very unstable, meaning the phosphoanhydride bond is easy to break. The cell "allows" it to break, but only at the cost of moving the phosphate to some other molecule, such as a serine or ...


18

Phospholipid bilayers found in cells are usually negatively charged. The phosphate groups repel each other by like charges and prevent two membranes from coming too close to each other. Membranes are also full of proteins and often coated with carbohydrates, which serve to keep membranes from interacting too strongly. See this diagram of a membrane bilayer: ...


17

An older answer that referred to the physiological feats of ancient humans, and why modern humans are wimps made me look up a couple of papers on running speeds a while ago. One of the examples used to support the statement that modern humans are "wimps" is a study of ancient fossilized footprints from Australia, which claim that the individuals making the ...


17

Birds have a body part known as the nicitating membrane otherwise known as the "third eyelid". This part has become vestigial in humans, where it remains as the plica semilunaris. This image of a masked lapwing clearly shows its nicitating membrane in action, where it covers the eye in a horizontal motion. This is analogous to blinking in humans, and the ...


16

I just weighed a pigeon tail feather (~10 cm) long. The mass was 0.05 g. Although all tail feathers are not equal in length (and all pigeons are not equal in size), this is probably a good approximation. Measuring the drag coefficient is going to be very challenging, because it will vary with the orientation of the oncoming airflow. A feather falling with ...


14

Although at first sight this might seem to be biology rather than physics, maintenance of human posture is an example of control theory. Indeed a quick Google will find many publications on it - I found a good review here. A standing human is a dynamical system that is not in equilibrium so it requires a (closed loop) feedback system to maintain it. This ...


12

Absolutely a serious part of research - quantum mechanics defines chemical structure and reactivity. Whenever you see a headline like 'Scientists find quantum effects important in protein activity, weird huh?', read it as 'Scientists find pragmatic classical approximations inadequate in describing protein activity'. In protein structure, for example, ...


12

The Cicada A careful study of the noise-making apparatus of the cicada can be found in a 1994 paper by Young and Bennet-Clark.$^1$ The authors generated sounds at about 0-16 kHz at peaks on the order of 100 dB using cicadas in various stages of deconstruction. The cicada uses a resonant organ-system called the tymbal which buckles and unbuckles rapidly to ...


10

Short answer The activation kinetics of Na+ channels are faster than K+ channels. Background Voltage-dependent channel gating basically occurs through three possible states of the channel: open, closed and inactivated (Fig. 1). Fig. 1. Gating of a voltage-activated sodium channel. Source: Balseiro Institute. Basically, ion channels are protein pores in ...


9

You can certainly get massive differences between EC50 and affinity. This is especially true for cell-based assays and membrane protein systems. The reason why is because the appropriate time scales to achieve binding equilibrium (hrs for nM affinity, days for picomolar, feptomolar affinity according to back of the envelope calculations) may be and likely ...


9

There are two factors that need to be taken into account here: 1. Myelination decreases membrance capacitance. The rate at which sodium influx through a node can depolarize the axon at the next node is related to both the current and capacitance across the membrane (in addition to a few other factors). So while adding a new node to the axon would indeed ...


9

Disclaimer: This is not my field of research. First, this is not a complete answer to our question. A nice explanation of the current hypothesis of water transport in trees (Dixon-Joly cohesion-tension theory, originally proposed 1894) can be found at The Amazing Physics of Water in Trees but also in Tyree (1997). The key points are that the stoma (leaf ...


9

Three facts: The K+ ions are heavily concentrated on the inside while the Na+ ions are heavily concentrated on the outside The Na+/K+ ion pump is unidirectional. It can only pump K+ ions inside the cell while expelling the Na+ ions. Finally only the Na+/K+ ion pumps can restore the ionic equilibrium. The full scene: Once the threshold is reached the ...


9

We should first understand what happens when a substance dissolves. During dissolution water interacts with the solute molecule; if the strength of interaction between the molecule and water is higher than the strength of interaction among the solute molecules then the solute dissolves. (Also have a look at this post). Phospholipid is an amphipathic ...


8

That quasi-travesty is the Nernst equation in $\log_{10}$ for a positive monovalent ion at physiological temperatures (37 degrees celsius), but they've hidden all that from you. Shame on them. The canonical form of the Nernst equation, for an ion $S$ is $$ E_{S} = \frac{RT}{z_{S}F}\ln{\frac{[S]_{out}}{[S]_{in}}} $$ where $R$ is the gas constant, $T$ is ...


8

No; the problem is, as you pointed out, that no organism will manage to multiply, grow or even sustain itself without absorbing matter to create new cells and fill metabolic losses. Even photoautotrophic organisms which get energy from light (which is in fact an E-M wave, so pretty close to electricity) collect matter from the environment -- plants for ...


8

Quick search - Some articles that may interest you: 1) Random walk model of insect movements Kareiva P. M., Shigesada N. (1983). Analyzing insect movement as a correlated random walk. Oecologia 56(2-3) 234-238 2) Artificial life model of flying insects and its comparison to real insects navigation strategies. Dale K., Collett T. C. (2001). Using ...


7

I think this question has more to do with kinetics / transport phenomenons than biology, but that's okay, everything is connected especially my computer to the internet. ;-) The basic idea behind transport phenomenons is that there will always be a flux of quantitative properties (e.g. charges, particle number, entropy, volume, etc...) where the qualitative ...


7

It is logically clear that the ankle could only partly be analyzed in the group of joints that are below its height. There is no direct way to measure the pressure on ankle joint (on talus bone), but from the logic it is clear that it should be the point of highest pressure in the group of points lister in the question, however the pressure is distributed ...


6

In what follows I am going to attempt to answer your question using a specific example of (competitive) reversible activation, and I hope to show what a misleading parameter EC50 can be. (Rate law derivation is an area of interest, hence the long-winded answer). It can of course give information, but IMO it needs to be used with extreme care. I am ...


6

The mechanism is called "capillary action". It requires a tube of a small diameter and happens because of the adhesion of water to the walls and the cohesion within the water (=surface tension).


6

if you are using NMR structures you might be making the mistake of using several superimposed structures - it would be nice to develop with x-ray structures at less than 2.0 A resolution for starters. Some of the models at low resolution can be sloppy, but submitted after 1994 or so will not have any center to center distances as that's when the x-ray ...


6

Since there seems to be several distinct sub-topics in your question, I will answer them one-by-one: 1). There are a variety of mechanisms that allow endothermic animals to maintain thermal homeostasis in a cold environment. The main ones are: a). The shivering response: When the core body temperature of a endotherm drops below a critical value (36.8C in ...


6

The System intracellular/membrane/extracellular space is well described by the model of a Concentration cell (see more on Wikipedia). The equation you mentioned is also called the Nernst equation. $$ E_{ion}= 62mV \biggl(\log\frac{[ion]_{outside}}{[ion]_{inside}}\biggr)= \frac{k_B T}{z e} \biggl(\ln\frac{[ion]_{outside}}{[ion]_{inside}}\biggr) $$ where ...


6

It isn't about heat but ultraviolet light. Melanin is the pigment that makes our skin colour whatever it is and in darker skin there's more melanin. Melanin dissipates UV, which otherwise would cause skin cancer as it introduces mutations into DNA. Melanin production is stimulated by UV so that's why tanning beds work, our body senses the danger and responds ...


6

Solar UV radiation is broadly classified as UV- A,B and C (Decreasing order of wavelengths). Penetrating ability of UV is a not a direct function of its wavelength; lesser the wavelength lesser is the penetrating ability (But higher is the energy: a direct function of wavelength). Penetration ability is dependent on scattering and absorption. Most ...


6

It is not the wavelength or frequency that determines light absorption- it is the energy of the photon that matters. The energy of incident light should match the excitation energy of the chromophore. The medium itself can also affect light absorption by electronically interacting with the chromophore. Wavelength plays a role in diffraction and therefore ...


6

I think inf3rno's answer is very complete, so I will just be adding some notes that might help OP understanding what's happening. Say that we increase the intracellular concentration of potassium by 10 mM, a +1 valence ion which contributes to POSITIVE membrane potential. Let's say we do that, in an in vitro cell model, using a syringe with only K⁺ ...


6

This question is really asking for examples, and the list of ways that knowledge of physics can be used in biology could be very long. However, here are a couple of examples: Systems ecology, especially with regard to energy and nutrient flow. This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem ...



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